Acute Cardiac Unloading and Recovery - Autumn 2017

Received
27 October 2017
Accepted
27 October 2017
Citation
Interventional Cardiology Review, 2017;
 
 
 
Foreword

Welcome to this special supplement of Interventional Cardiology Review. This supplement is devoted to the proceedings of the second annual Acute Cardiac Unloading and REcovery (A-CURE) Working Group meeting, which was held on 25 August 2017 in Barcelona, Spain. The A-CURE Working Group is comprised of leading academic experts in clinical and basic cardiac research and is dedicated to advancing the science and clinical application of acute cardiac unloading. This meeting also brought together experts from multiple disciplines, including interventional cardiologists, heart failure specialists, cardiac surgeons, molecular biologists and biomedical engineers.

Cardiac traumas such as myocardial infarction (MI), myocarditis, cardiomyopathy and cardiogenic shock impair the ability of the heart to pump blood, resulting in end organ failure and, ultimately, death. Most therapeutic approaches to these traumas aim to maintain cardiac output but, in the process, impose further stress on the heart. This meeting focused on the use of new technologies in the treatment of these traumas. Acute cardiac unloading decreases myocardial oxygen consumption and maximises the ability of the heart to rest and recover after damage. Mechanical unloading employs percutaneously inserted ventricular assist devices such as the FDA-approved and CE-marked Impella family of devices, the Tandem Heart and the Investigational HeartMate PHP.

This supplement features a number of presentations covering a broad range of subjects related to cardiac unloading. The first sessions were devoted to the basic science underlying the concept of mechanical unloading. The meeting began with a presentation by Daniel Burkhoff describing the basic science behind acute ventricular and myocardial unloading. This was followed by Navin Kapur, who provided some insights into the molecular basis of mechanical unloading, describing the mechanism of cardioprotection at the cellular level. Gene therapy is receiving considerable current interest as a therapeutic strategy in heart failure (HF). Roger Hajjar presented data in support of his hypothesis that acute mechanical unloading using the Impella may improving gene delivery by enhancing viral uptake. Jacob Møller closed the first session by comparing the differential haemodynamic responses of Impella and extracorporeal membrane oxygenation (ECMO) support in a new large animal model of cardiogenic shock.

In the second session, which discussed progress towards a clinical mandate for cardiac unloading, Carsten Tschöpe examined the role of acute mechanical unloading as a bridge to recovery in patients with fulminant myocarditis. Babar Basir described the Detroit Cardiogenic Shock Initiative, which has produced a protocol for the treatment of cardiogenic shock. Finally, Perwaiz Meraj presented details of the first prospective feasibility study to evaluate the use of the Impella CP pump for unloading of the left ventricle prior to primary percutaneous coronary intervention in patients presenting with acute ST-segment elevation MI. The morning ended with three talks from featured abstracts: Carlos Del Rio presented data from his investigation into how mechanical support may affect the mechano-energetic relationship in the heart, Silvia Burchielli described a study that showed that cardiorespiratory support in a swine model of acute MI was able to drastically reduce mortality and provide an effective bridge to reperfusion, and Kiyotake Ishikawa discussed his innovative research demonstrating that left ventricle support using Impella reduces left atrial stretch and inhibits atrial arrhythmias through reduced oxidative stress.

The afternoon’s presentations had a stronger focus on the clinical applications of ventricular unloading. The keynote speaker, Valentin Fuster, discussed the evolution of cardiovascular disease therapy, including identifying risk at early stages of life, treating subclinical disease and the challenges of treating older patients. Elazar Edelman discussed the use of hysteresis loops generated by support devices to track cardiac function. Mark Anderson described the clinical applications of the Impella RP, which is designed for right heart support. Ralf Westenfeld discussed the role of Impella support in facilitating pulmonary decongestion in cardiogenic shock. This session ended with Dirk Westermann discussing the use of the combination of ECMO and Impella support in cardiogenic shock.

The meeting concluded with two talks from selected abstracts. Kapil Lotun presented a study investigating mechanical circulatory support during cardiac arrest. In addition, Daniel Scheiber, the Young Investigator Scholarship awardee, described his research demonstrating that mitochondrial reactive oxygen species production is reduced in the left ventricle of mechanically unloaded hearts.

The presentations highlighted some exciting new developments and represent the substantial advances in the field of acute myocardial unloading and recovery in the last year. The A-CURE Working Group meeting is unique in involving a diverse group of experts from multiple disciplines within a unique setting.

Interventional Cardiology Review would like to thank all expert reviewers who contributed towards this edition. A special thanks goes to our Editorial Board for their continued support and guidance. We hope that you find this supplement informative and interesting.

Perspectives on Acute Unloading

Dr Burkhoff is an Associate Professor of Medicine at Columbia University, Division of Cardiology. He has authored more than 300 peerreviewed publications and is a world expert in heart failure, haemodynamics, and heart muscle mechanics. Dr Burkhoff is a founding member of the A-CURE Working Group and Co-Chair of the 2017 A-CURE Symposium.

Dr Burkhoff introduced the meeting by emphasising the need for consistent terminology in the field of acute cardiac unloading. The proposed definition of unloading is the reduction of total mechanical power expenditure of the ventricle, which correlates with reductions in myocardial oxygen consumption and haemodynamic forces that lead to ventricular remodelling.

The aim of myocardial unloading is twofold: first to achieve myocardial salvage and second to prevent heart failure (HF) and cardiac remodelling. It is important to recognise these as two distinct and important goals of acute cardiac unloading.

The benefits of left venticle (LV) unloading are well documented in both basic and clinical literature. Pharmacological unloading using captopril, an angiotensin-converting enzyme inhibitor, in an animal model of myocardial infarctino (MI) was first reported in 1985, and showed a shift in the end diastolic pressure.1 Following this initial study, the shift from basic to clinical research occurred rapidly. Clinical trials showed that, after anterior MI, ventricular dilation is progressive and that captropril may curtail the process, as well as reducing filling pressures and improving exercise tolerance.2

However, there are inherent limitations to pharmacological approaches to myocardial unloading. Unloading the LV and decreasing heart rate by these methods leads to a corresponding compromise in aortic pressure and cardiac output. Appropriate device-based therapies can overcome these limitations, as well as facilitating optimal use of other pharmacological or device-based therapies. These can have synergistic effects.

A 2003 study by Meyns et al. showed that by providing LV support using a catheter-mounted axial flow pump during the ischaemic period and during reperfusion the infarct size was reduced in animal models. Furthermore, oxygen demand during unloading is not an ‘allor- nothing’ phenomenon, but there is a dose-dependence; the more unloading is achieved, the more oxygen demand can be reduced during the ischaemic period and during reperfusion, and the more myocardial salvage can be achieved.3 Since the publication of this study, a growing body of literature has established the benefits of mechanical myocardial unloading,4–8 and has led to the increased clinical application of the technique.

The difference between myocardial unloading using drugs and devices can be demonstrated by examining the impact of LV-aorta (LV-Ao) assist devices on haemodynamics and energetics. An LV-Ao device takes blood directly from the LV to the aorta and maintains systemic and coronary perfusion pressures while simultaneously unloading the ventricle – a phenomenon known as LV-aortic pressure uncoupling.

Figure 1: Determinants of myocardial oxygen consumption

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Uncoupling the LV from the systemic circulation minimises the mechanical work of the heart. This concept is the essence of the differences between drugs and devices and explains why devices are more effective than drugs alone in unloading the LV.

Dr Burkhoff emphasised that the determinants of myocardial oxygen consumption are not solely determined by the stroke work of the heart. This is important to remember when comparing different modes of mechanical circulatory support such as the left ventricular assist device (LVAD), which takes blood from the LV to the aorta and ECMO, which takes blood from the right atrium to the aorta. The oxygen consumption of the heart is linearly related to a parameter known as the pressure volume area (PVA) (see Figure 1). This is the sum of the stroke work and the potential energy, i.e. the energy that is stored in the myocardial filaments after contraction rather than being released as external work. It is also important to note that even when the heart is producing no external work, it still consumes energy, largely due to calcium cycling, but also due to basal metabolism. As drugs increase contractility, they increase oxygen consumption independent of the increased workload of the heart because of the increased energy requirement for calcium cycling.

Figure 2: The 'dose-dependence' of myocardial support and unloading

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It is also important to understand that the effects of unloading are not restricted to the acute phase, and ventricular support has known consequences on ventricular remodelling associated with HF. Longterm mechanical unloading of the failing ventricle can, under certain conditions, lead to reverse remodelling, a restoration of a normal pressure-volume relationship in failing heart. Sustained unloading offers the potential for significant and sustained myocardial recovery through this reverse remodelling process; this was first reported in human hearts in 1996.9

Studies of LV unloading are still in their infancy but basic research is accelerating, and clinical studies are in their early stages. Therefore, Dr Burkhoff stressed the need to introduce consistency in the literature and into clinical studies, not only in terminology, but also in methodologies. We need to think critically of the methodologies that are being used, particularly in terms of measuring pressure-volume loops. It is difficult to compare studies that enrol different patient populations. It is also important to be consistent in the definition of clinical trial endpoints.

With respect to terminology, it is essential to understand the difference between support and unloading, and their dose-dependence (see Figure 2). Partial support and partial unloading occurs when the heart continues to provide some of the cardiac output while the device provides the remainder. This results in decreased myocardial oxygen demand and a small reduction in the PVA. In full support/partial unloading, the entire cardiac output is provided by the device, and there is still a volume cycle in the ventricle to generate some LV pressures throughout the cardiac cycle. In this scenario, the aortic pressure is uncoupled from ventricular function, and the pressure-volume loop shifts further leftwards and myocardial oxygen consumption is further decreased. Only when the ventricle is fully unloaded and the heart is performing zero work, i.e. during full support/full unloading, is myocardial oxygen consumption minimised. This shifts the pressurevolume relationship further leftward, almost obliterating the PVA. This emphasises the fact that unloading is dose-dependent and, in clinical practice, the flow rate of a device may have a different impact on different patients depending on their loading conditions that result from the use of the device.

In his closing remarks, Dr Burkhoff also highlighted the Training and Education in Advanced Cardiovascular Haemodynamics (TEACH) training initiative that aims to enhance the understanding of basic haemodynamic principles. This will involve two courses that will be held at Transcatheter Cardiovascular Therapeutics (TCT) Annual Meeting 2017 (www.tctmd.com, www.crfteach.com and www.pvloops.com).

References

  1. Pfeffer JM, Pfeffer MA, Braunwald E. Influence of chronic captopril therapy on the infarcted left ventricle of the rat. Circ Res 1985;57:84–95.
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  2. Pfeffer MA, Lamas GA, Vaughan DE, et al. Effect of captopril on progressive ventricular dilatation after anterior myocardial infarction. N Engl J Med 1988;319:80–6.
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  3. Meyns B, Stolinski J, Leunens V, et al. Left ventricular support by catheter-mounted axial flow pump reduces infarct size. J Am Coll Cardiol 2003;41:1087–95.
    Crossref | PubMed
  4. Kapur NK, Paruchuri V, Urbano-Morales JA, et al. Mechanically unloading the left ventricle before coronary reperfusion reduces left ventricular wall stress and myocardial infarct size. Circulation 2013;128:328–36.
    Crossref | PubMed
  5. Kapur NK, Qiao X, Paruchuri V, et al. Mechanical preconditioning with acute circulatory support before reperfusion limits infarct size in acute myocardial infarction. JACC Heart Fail 2015;3:873–82.
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  6. Doenst T, Bugger H, Leippert S, et al. Differential gene expression in response to ventricular unloading in rat and human myocardium. Thorac Cardiovasc Surg 2006;54:381–7.
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  7. Derwall M, Brücken A, Bleilevens C, et al. Doubling survival and improving clinical outcomes using a left ventricular assist device instead of chest compressions for resuscitation after prolonged cardiac arrest: a large animal study. Crit Care 2015;19:123.
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  8. Anderson MB, Goldstein J, Milano C, et al. Benefits of a novel percutaneous ventricular assist device for right heart failure: The prospective RECOVER RIGHT study of the Impella RP device. J Heart Lung Transplant 2015;34:1549–60.
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  9. Birks EJ, Tansley PD, Hardy J, et al. Left ventricular assist device and drug therapy for the reversal of heart failure. N Engl J Med 2006;355:1873–84.
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Insights into the Molecular Basis of Acute Cardiac Unloading and Cardioprotection

Dr Kapur is an Associate Professor and Executive Director of Cardiovascular Center for Research and Innovation Tufts Medical Center in Boston. His research focuses on acute and chronic heart failure, circulatory support device development, and cardioprotective mechanisms in the setting of acute myocardial infarction. Dr Kapur is founding member of the A-CURE Working Group, and Co-Chair of the A-CURE Symposium.

Dr Kapur began by presenting an overview of the history of left ventricle (LV) unloading over the past decade. He noted that mechanical devices developed in recent years have provided hope for heart failure (HF) patients who previously had no options. The mechanical devices that have been employed for unloading have developed from biventricular devices (BVADs) and HeartWare® HVAD® pumps, where the aim was cardiac replacement as bridge to transplant or destination therapy, to an increasing use of percutaneous technologies such as the Impella pumps, where the goal is cardiac recovery and not replacement. He highlighted that percutaneous heart pumps have given clinicians the chance to promote the recovery of a patient’s native heart.

He then presented a brief history of the A-CURE movement, which began in Boston in 2015 and has since hosted meetings in Paris and Rome prior to this meeting in Barcelona. In those 2 years, research has progressed rapidly from preclinical testing to clinical trial launch. However, despite considerable progress in the field of LV unloading, questions remain, notably whether we can reduce the burden of ischaemic HF after a myocardial infarction (MI), and what are the cardioprotective mechanisms underlying LV recovery.

Myocardial infarct size remains an important target of therapy.1 However, even if infarct size is reduced following an MI, if the haemodynamics are consistent with HF, this will remain a major cause of mortality for patients.2 Two years ago, Dr Kapur’s team published the concept of the primary unloading hypothesis, which suggested that first unloading the LV, then delaying reperfusion, activates a cardioprotective programme that limits myocardial damage in acute MI (Figure 1).3 This study also identified an early molecular signal, release of the cytokine stromal-derived factor 1 alpha (SDF-1-alpha), which is known to be cardioprotective. This correlated with infarct size and led to the hypothesis that mechanical unloading leads to an increase in the SDF-1 CXCR4 signalling pathway, which is linked to a number of other cardioprotective mediators, including protein kinase B, extracellular signal-regulated kinase and glycogen synthase kinase 3 beta. This results in a shift to a cardioprotective phenotype.

Another important question concerns the kinetics of primary unloading: how important is the delay to reperfusion? Dr Kapur’s team tested the idea of delaying reperfusion after activating the Impella device by 15, 30 or 60 minutes. Delaying reperfusion appeared to be necessary for reducing infarct size (see Figure 2).4 One possible reason for this is that functional reperfusion may reduce the area of risk. With the left anterior descending artery (LAD) still occluded, enhanced collateral flow through non-occluded vessels may lead to a reduction in the area at risk. This may, in part, drive the benefits in terms of reducing infarct size.

Figure 1: The primary unloading hypothesis

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Figure 2: Effect of delaying reperfusion

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The release of SDF-1-alpha in ventricular tissue is highest after a 30-minute delay in reperfusion. In order to fully understand the biological mechanisms underlying unloading, it was important to explore the cause of this release. SDF-1-alpha is ubiquitously expressed, but is rapidly degraded by a number of metalloproteases as well as dipeptidyl peptidase-4 (DPP4) and the CXCR7 pathway.5 Further study revealed that primary unloading reduces the activity of these proteases that promote SDF-1-alpha degradation. Dr Kapur’s team is currently investigating the hypothesis that, by reducing the activity of these degradation pathways, primary unloading can increase the concentration of SDF-1- alpha in the myocardium, particularly during acute injury, leading to a protective phenotype that increases cell survival (Figure 3).6 It is known that ischaemic injury leads to an uncoupling of SDF-1-alpha and CXCR signalling.7 Dr Kapur suggested that primary unloading re-aligns the SDF- 1-alpha:CXCR signalling axis, which is vital for myocardial repair.

Figure 3: Effect of primary unloading in the myocyte at the molecular level

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An important question to address was whether the acute cardioprotective effect of primary unloading provides a durable reduction in HF. The cardiac response to increased work includes a reactivation of foetal genes, and remodelling following acute MI is largely driven by the foetal gene programme.8 An animal study found that, compared to primary reperfusion, primary unloading reduces LV scar and preserves cardiac output at 30 days after acute MI.6 No early signs of change in cardiac volume were seen but this may be due to the short timescale of the study. The study also showed that, at 30 days, primary unloading limits the activation of a gene programme associated with maladaptive cardiac remodelling. It also reduces tissue expression and circulating levels of brain natriuretic peptide, an important marker of HF, and increases the circulating levels of SDF-1-alpha in the first week, which correlates directly with reduction of scar size. Primary unloading appears to mechanically reprogramme myocardial responses to injury in acute MI, which involves the foetal gene programme.9

In summary, research to date has provided a platform for further investigation. Administration of primary unloading and stabilising haemodynamics following acute MI offer the potential for interventions that have until now been considered impossible. These include the administration of adjunct pharmacotherapy during an anterior STEMI including intravenous beta blockade, intracoronary vasodilators, glucose, insulin, potassium, SDF-1-alpha, protease inhibitors, and neuromodulation. Current research is investigating the administration of intravenous esmolol during primary unloading to increase the oxygen supply:demand ratio.

Dr Kapur concluded by reminding the audience that, in 2015, it was predicted that mechanical preconditioning would not translate into a successful clinical strategy that reduces myocardial infarct size.10 In 2017, the US Food and Drug Administration approved a Phase I clinical trial examining the safety and feasibility of primary unloading.

References

  1. Stone GW, Selker HP, Thiele H, et al. Relationship between infarct size and outcomes following primary PCI: patientlevel analysis from 10 randomized trials. J Am Coll Cardiol 2016;67:1674–83.
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  2. Desta L, Jernberg T, Lofman I, et al. Incidence, temporal trends, and prognostic impact of heart failure complicating acute myocardial infarction. The SWEDEHEART Registry (Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies): a study of 199,851 patients admitted with index acute myocardial infarctions, 1996 to 2008. JACC Heart Fail 2015;3:234–42.
    Crossref | PubMed
  3. Kapur NK, Qiao X, Paruchuri V, et al. Mechanical preconditioning with acute circulatory support before reperfusion limits infarct size in acute myocardial infarction, JACC Heart Fail 2015;3:873-82.
    Crossref | PubMed
  4. Zhang Y, Schnitzer G, Eposito M, et al. Gene expression profiles underlying the cardioprotective effects of mechanical primary unloading of the left ventricle before reperfusion in acute myocardial infarction. Circulation 2016;134:A19156.
  5. Zhong J, Rajagopalan S. Dipeptidyl peptidase-4 regulation of SDF-1/CXCR4 axis: implications for cardiovascular disease. Front Immunol 2015;6:477.
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  6. Kapur NK. Journal of Cardiovascular Translational Research 2017. In press.
  7. Penn MS. Importance of the SDF-1:CXCR4 axis in myocardial repair. Circ Res 2009;104:1133–5.
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  8. Whelan RS, Mani K, Kitsis RN. Nipping at cardiac remodelling. J Clin Invest 2007;117:2751–3.
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  9. Depre C, Shipley GL, Chen W, et al. Unloaded heart in vivo replicates fetal gene expression of cardiac hypertrophy. Nat Med 1998;4:1269–75.
    Crossref | PubMed
  10. Bates ER. Limiting infarct size in ST-segment myocardial infarction: the holy grail of reperfusion therapy. JACC Heart Fail 2015;3:883–5.
    Crossref | PubMed
Impella Support and Cardiac Gene Therapy for Heart Failure

Dr Hajjar is the Director of the Cardiovascular Research Center and the Arthur and Janet C Ross Professor of Medicine at the Mount Sinai School of Medicine. His research focuses on molecular mechanisms of heart failure (HF) and his team has validated the cardiac sarcoplasmic reticulum calcium ATPase pump (SERCA2a) as a target in HF, developed methodologies for cardiac-directed gene therapy, examined the functional consequences of SERCA2a gene transfer in the failing heart, and conducted first-in-man clinical trials testing the efficacy of gene transfer in patients with HF. Dr Hajjar is a founding member of the A-CURE Working Group.

Dr Hajjar began by examining the role of gene therapy in HF. He drew a distinction between cellular therapy, which allows the introduction of new cells that can help the remodelling of damaged or diseased myocardium or extracellular matrix, and gene therapy, which focuses on altering the function of diseased cardiac cells at the level of the single gene. In the last decade there has been invigorated interest in cardiac gene therapy as a result of increasingly efficient gene transfer technologies and safer vectors that allow the homogeneous transduction of cardiomyocytes. Critical advances that have supported the increased use of gene therapy include the ability to induce long-term expression of the target gene, viral vectors with higher cardiac specificity and minimally invasive vector delivery techniques.1,2 Dr Hajjar’s team is investigating gene replacement therapy using adeno-associated virus (AAV) vectors delivering the SERCA2a gene. These vectors have been demonstrated to be safe and non-pathogenic; the majority of the population has been exposed to the wild-type virus in childhood without any evidence of disease.

The efficiency of gene transfer is has been a major obstacle to the successful translation of gene therapy into the clinic. The rate of in vivo viral transduction reported in clinical trials is too low to induce any physiological impact. The efficiency of gene transfer to the heart can be improved by increasing perfusion pressure, coronary flow, vector dose, and dwell time. The preferred method of administering the vector is through percutaneous intracoronary artery infusion, since this approach more readily ensures gene delivery to the viable myocardium. The Calcium Up-Regulation by Percutaneous Administration of Gene Therapy In Cardiac Disease (CUPID) clinical trials investigated this method of intracoronary administration of AAV type 1 (AAV1)/SERCA2a in patients with Class III/IV HF. CUPID 1 was a randomised, doubleblind, placebo-controlled, Phase IIa study in patients with advanced HF. Following the administration of intracoronary AAV1/SERCA2a or placebo, significant increases in time to clinical events and decreased frequency of cardiovascular events were observed at 12 months in the treatment group (hazard ratio=0.12; P=0.003), and mean duration of cardiovascular hospitalisations over 12 months was substantially decreased (0.4 versus 4.5 days; P=0.05) on high-dose treatment versus placebo.3

The follow-up and larger Phase IIb study (CUPID 2) is the largest gene transfer study carried out in humans to date (n=250). However, AAV1/SERCA2a at the dose tested did not show an improvement in the primary endpoint.4 Possible reasons for this disappointing result include insufficient myocardial uptake, because the AAV concentration was too low (the US Food and Drug Administration did not allow the use of higher doses), and the method of gene transfer was inadequate. While previous data in animals had showed a high percentage of infected cardiomyocytes (30–75 %), data from CUPID 2 showed that the uptake in humans was much lower (<0.5–1 %). The method of gene transfer in CUPID 2 trial was clearly inadequate.

Figure 1: Coronary occlusion with and without left ventricular support

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Dr Hajjar presented his current hypothesis that involves improving gene delivery by using the Impella device to enhance viral uptake. He proposed that Impella support could affect uptake in two ways. First, viral uptake is adversely affected by increased left ventricle (LV) diameter, end diastolic pressure and sympathetic activation, leading to increased wall stress. Further, the inflammation, cell death, ischaemia and myocyte destruction at the time of a myocardial infarction (MI) also provides a hostile environment for vectors. Acute unloading with the Impella mitigates these adverse conditions. Second, the Impella could be used to haemodynamically support the patient while the vector is delivered into the coronary system during temporary coronary balloon occlusion. This would allow for a longer dwell time and minimise the risk of haemodynamic collapse.

Dr Hajjar presented data from his current studies. In a porcine model of subacute ischaemic HF, MI is induced, and the heart is allowed to remodel for 2 weeks. Gene delivery under Impella support then commences at this time point. Early data shows that this approach reduces LV wall stress, decreases end diastolic pressure, increases epicardial coronary flow, and increases myocardial perfusion, specifically in the infarct region (see Figure 1).5 Thus far, all pigs receiving Impella support during vector delivery while occluding the coronary artery have been successfully bridged through the procedure without incident, while all pigs that did not receive mechanical support suffered haemodynamic collapse and required cardioversion or other intervention.

In conclusion, these ongoing studies hope to demonstrate that by enhancing coronary flow, perfusion pressure can be increased while at the same time the unloading will allow a better environment for more aggressive gene delivery.

References

  1. Kawase Y, Ladage D, Hajjar RJ. Rescuing the failing heart by targeted gene transfer. J Am Coll Cardiol 2011;57:1169–80.
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  2. Hayward C, Patel H, Lyon A. Gene therapy in heart failure. SERCA2a as a therapeutic target. Circ J 2014;78:2577–87.
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  3. Jessup M, Greenberg B, Mancini D, et al. Calcium upregulation by percutaneous administration of gene therapy in cardiac disease (CUPID): a phase 2 trial of intracoronary gene therapy of sarcoplasmic reticulum Ca2+- ATPase in patients with advanced heart failure. Circulation 2011;124:304–13.
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  4. Greenberg B, Butler J, Felker GM, et al. Calcium upregulation by percutaneous administration of gene therapy in patients with cardiac disease (CUPID 2): a randomised, multinational, double-blind, placebo-controlled, phase 2b trial. Lancet 2016;387:1178–86.
    Crossref | PubMed
  5. Hajjar R. J Cardiovasc Transl Res 2017. In press.
Comparative Haemodynamic Response to Impella Versus Extracorporeal Membrane Oxygenation Support in a Porcine Cardiogenic Shock Model

Professor Møller is a Professor and Head of Cardiac Research at Odense University Hospital Denmark. Professor Møller has published more than 160 peer-reviewed articles. His research focuses on cardiogenic shock, myocardial infarction, heart failure, valvular disease, and controlled clinical trials. Professor Møller is founding member of the A-CURE Working group.

Prof Møller opened his talk by emphasising the importance of understanding the whole concept of unloading the heart in a clinical setting, particularly in patients with cardiogenic shock (CS). Despite the urgent need for experimental research in the field of CS, there are limited options in large animal models enabling research using devices applied to human subjects. Since it is impossible to conduct controlled haemodynamic studies at the bedside in patients with CS undergoing mechanical circulatory support, Prof Møller’s team is developing an animal model that mimics severe CS after myocardial infarction. This aim of this model is to allow for detailed haemodynamic assessment of the CS state. However, inducing CS in large animal is associated with unacceptably high rates of premature mortality and the inability to acquire a complete data recoding. An ideal model would avoid this, would anatomically mimic humans, and would allow for the placement of a device percutaneously in the same manner as in the catherterisation laboratory.

Prof Møller’s work has focused on porcine models for the various size advantages they have compared to other animals. In particular, large porcine models allow for the placement of multiple catheters, enabling monitoring of the heart and peripheral perfusion. The induction of CS was based on an earlier model that involved the repeated injection of plastic microspheres into the left main coronary artery. In this model, this causes microembolisation in the coronary circulation and stepwise elevations of left ventricle end-diastolic pressure (LVEDP).1 The new model uses Contour embolisation particles, which are small and irregular flakes of polyvinyl alcohol 45–150 microns in diameter. Serial injections of these particles into the coronary circulation allows precise control of the degree of CS, ultimately producing increased lactate and severe LV failure (see Figure 1). Of note, induction of CS using this model was achieved in a study of 16 animals without the loss of a single animal. The pressure-volume loops from the LV confirmed the low pressurevolume area (PVA), demonstrating the severity of the CS. This model also allowed percutaneous placement of an extracorporeal membrane oxygenation (ECMO) cannula and an Impella CP® assist device, aiming to mimic conditions that would be used in the catheterisation laboratory.

Figure 1: Controlled cardiogenic shock in a porcine model

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This model was employed in a study that aimed to compare active unloading with the Impella CP to VA-ECMO in large pigs with profound acute CS. The clinical endpoints were PVA, LVEDP and organ perfusion. Following the induction of profound CS, six pigs were treated with VA-ECMO, and six pigs treated with the Impella CP.2 As expected, the afterload was increased with ECMO, and the pressure-volume loop initially shifted rightward (reflecting increased myocardial work), but eventually resulted in a small leftward shift, likely reflecting the recovery of contractility while on support. In contrast, the Impella was found to provide almost full support immediately, giving partial unloading with low pulsatility, then the LV recovered. The PVA and LVEDP were significantly higher in CS pigs treated with the ECMO compared with Impella. Lactate was normalised in both groups. However, the ECMO-treated animals immediately restored renal perfusion, and this aspect was more efficient than the Impella.

In conclusion, this study confirms the ability of the Impella CP to unload the heart efficiently and effectively while providing increased tissue perfusion. However, ECMO is superior in restoring systemic perfusion in the acute stages of support. Chronic studies would be necessary to assess the effect of both platforms on restoring systemic perfusion relevant to the clinical setting.

References

  1. Smiseth OA, Mjøs OD. A reproducible and stable model of acute ischaemic left ventricular failure in dogs. Clin Physiol 1982;2:225–39.
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  2. Moller JE. J Cardiovasc Transl Res 2017. In press.
Institutional Algorithms, Mechanical Circulatory Support & Patient Outcomes: The Detroit Cardiogenic Shock Initiative

Dr. Basir is an Interventional Fellow at the Henry Ford Hospital in Detroit, Michigan.

Dr Basir commenced his presentation by reminding the audience that, despite the fact that the number of cases of cardiac shock (CS) during acute myocardial infarction (AMI) has steadily risen,1 the rates of in-hospital mortality have remained unchanged for more than 20 years.2 A group of physicians, including Dr Basir, examined the Abiomed Impella Quality (IQ) database on Impella use, with the aim of identifying factors that may be associated with survival. They used this information to derive an institutional protocol that could be systemically implemented across several hospitals in the region of the Henry Ford Hospital. This prospective approach was focused on improving survival in this patient population. Of note, there is a wide variation in outcomes with Impella use across different sites: IQ data (791 sites supporting >4 patients with AMI CS, 15,529 patients total) show that the bottom 20 % performing sites have a mean survival of only 30 %, whereas the top 20 % of sites have a higher volume of Impella utilisation and a mean survival of 76 %. In 2016, the mean survival rate was 58 %, a relative improvement of 14 % since the US Food and Drug Administration (FDA) approval on the Impella.3

One factor observed to be associated with early mortality in AMI/CS is increased inotrope exposure.4 This does not determine causality as the severity of a patient’s condition correlates with the number of inotropes and vasopressors. Nevertheless, it is likely that the load of inotropes and vasopressors directly influences outcomes.5 Similarly, a delay in support is clearly associated with mortality in AMI/CS. Data indicate that if a patient receives mechanical circulatory support (MCS) in the first 75 minutes following AMI, outcomes are substantially improved compared with those who have a longer delay in support (see Figure 1).5 In addition, the use of haemodynamic support prior to percutaneous coronary intervention (PCI) has been shown to improve survival, due to effects on the reperfusion injury and ischaemia (see Dr Navin Kapur’s talk). The separation of the Kaplan–Meier curves occurs very early following PCI, reinforcing the idea that early MCS is a key determinant in clinical outcomes (see Figure 2).5

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These factors have been used to develop a protocol for use by the Detroit Cardiogenic Shock Initiative (CSI), a collaboration between four hospitals in Detroit, under the leadership of Dr William O’Neill, with the aim of increasing survival in MI/CS (see Figure 3).6 This protocol is specific to a defined group of patients, and has proscribed exclusion and inclusion criteria. Although this was a protocol-led treatment, individual decisions were based on operator preference. Nevertheless, this approach allows for better assessment of real-world outcomes. The protocol was comprised of early detection of CS, immediate catheterisation laboratory activation, mechanical support prior to PCI, invasive haemodynamic monitoring, decreased vasopressor/inotrope use and early escalation to a larger support device if needed (cardiac power output < 0.6 W and a pulmonary artery pulsatility index <0.9). Quality measures include doorto- support time of less than 90 minutes, establishment of Thrombolysis In Myocardial Infarction (TIMI) III flow, weaning of vasopressors and inotropes, maintaining a cardiac power output in excess of 0.6 W and improving survival to discharge.

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Using this protocol, the Detroit CSI pilot study has been initiated and has treated 41 patients at the time of the A-CURE Symposium. The average age of participants was 65 years, and 70 % were male. A total of 95 % were taking vasopressors and 41 % were in cardiac arrest.6 This patient populations is similar to that of the SHOCK trial (n=302).7 The population differed from that in the Impella versus Intra-Aortic Balloon Pump in Cardiogenic Shock (IMPRESS) trial (n=48), a prospective trial in which the patients were much sicker, all were mechanically ventilated and 92 % had a cardiac arrest.8 In the Detroit CSI study, the median lactate levels were 4.7 g/dl compared with 8.2 g/dl in the IMPRESS trial.

Of 55 screened patients, 14 were excluded based on the inclusion/ exclusion criteria. The pilot study showed favourable outcomes. Outof- hospital cardiac arrest occurred in 6 participants and there were 11 in-hospital cardiac arrests. Overall survival rate was 76 %, compared with 53 % in the SHOCK trial and 53 % in IMPRESS.7,8 Implantation of Impella prior to PCI occurred in 66 % of participants and there was a 66 % improvement in cardiac power output (0.57 W to 0.95 %; P<0.001) after the initiation of MCS and PCI. Of note, as the study progressed, protocol adherence increased, with a corresponding improvement in outcomes.6

In conclusion, rapid early delivery of MCS guided by invasive haemodynamic monitoring is associated with significantly improved survival in an AMI/CS patient population. This multi-institutional effort demonstrates the effectiveness of an institutionalised protocol to address CS and significantly improve patient outcomes in this difficult patient cohort. Dr Basir described this as a “war on shock”, which involves a systematic team effort using regional shock protocols that can be summarised as follows:

A – Access
B – Basic Haemodynamics (blood pressure, left ventricular end diastolic pressure and cardiac power output)
C – Circulatory Support
D – Decrease vasopressors and inotropes
E – (Early) Escalation.

References

  1. Sandhu A, McCoy LA, Negi SI, et al. Use of mechanical circulatory support in patients undergoing percutaneous coronary intervention: insights from the National Cardiovascular Data Registry. Circulation 2015;132:1243–51.
    Crossref | PubMed
  2. Jeger RV, Radovanovic D, Hunziker PR, et al. Ten-year trends in the incidence and treatment of cardiogenic shock. Ann Intern Med 2008;149:618–26.
    Crossref | PubMed
  3. Abiomed, Impella Quality (IQ) Database, US AMI/CGS January 2009-Dec 2016. Survival to Explant.
  4. Samuels LE, Kaufman MS, Thomas MP, et al. Pharmacological criteria for ventricular assist device insertion following postcardiotomy shock: experience with the Abiomed BVS system. J Card Surg 1999;14:288–93.
    Crossref | PubMed
  5. Basir MB, Schreiber TL, Grines CL, et al. Effect of early initiation of mechanical circulatory support on survival in cardiogenic shock. Am J Cardiol 2017a;119:845–51.
    Crossref | PubMed
  6. Basir MB. J Cardiovasc Transl Res 2017b. In press.
  7. Hochman JS, Sleeper LA, Webb JG, et al. Early revascularization in acute myocardial infarction complicated by cardiogenic shock. SHOCK Investigators. Should we emergently revascularize occluded coronaries for cardiogenic shock. N Engl J Med 1999;341:625–34.
    Crossref | PubMed
  8. Ouweneel DM, Eriksen E, Sjauw KD, et al. Percutaneous mechanical circulatory support versus intra-aortic balloon pump in cardiogenic shock after acute myocardial infarction. J Am Coll Cardiol 2017;69:278–87.
    Crossref | PubMed
Paradoxical Mechano-energetic Costs of Acute Mechanical Intra-ventricular Unloading

Dr. del Rio is a Research Scientist at MyoKardia in San Francisco, California. He was the recipient of the Best in Research Scholarship for the 2017 A-CURE Symposium.

Dr Del Rio presented data from his investigation into how mechanical support may fundamentally alter the mechano-energetic relationship in the heart. He began by providing the background to his study. By design, durable intra-cardiac left ventricular assist devices (LVAD) support the systemic circulation and cardiac output by removing blood from the left ventricle (LV), resulting in preserved systemic pressures and decreased stroke work (SW), stroke volume, filling pressures and preload. Unfortunately, these beneficial effects have not translated to recovery of heart function in these patients. In questioning this, Dr Del Rio examined the determinants of oxygen consumption in the left heart, particularly contractility and haemodynamic load. Historically, researchers have assumed that the heart does not respond to its altered physiological state resulting from implantation of an LVAD. Dr Del Rio’s team proposed the hypothesis that LVAD support can lead to paradoxical increases in the effective arterial elastance (Ea) and intrinsic cardiac contractility during ventriculoarterial coupling, therefore hindering mechano-energetic unloading.1 This imposes an intrinsic barrier to achieving LVAD-mediated recovery/reverse remodelling.

Dr Del Rio described an experiment in which an LVAD was inserted into a healthy animal and provided chronic partial support (>70 % of cardiac output). Over the course of 7 weeks, rather than maintain a steady state of lower device-dependent LV end diastolic volumes, the preload increased despite LVAD support. The Ea also showed an acute increase that normalised over time as the LV end diastolic pressure increased. There was a concomitant increase in early contractility, increased ventricle fibrosis and early release of atrial natriuretic peptide (ANP). There was an acute increase in contractility and an increase in fibrosis of the ventricle. This suggested that chronic partial support in healthy animals may trigger LV remodelling.

A subsequent study assessed the acute effects of LVAD support on systemic haemodynamics, LV mechano-energetics, and myocardial oxygen consumption (MVO2) in vivo.2 The study involved 12 mixedbreed sheep (34 to 54 kg), which were given acute LVAD support. The study assessed MVO2, using coronary sinus/arterial sampling catheters and left circumflex artery [LCX] coronary flow probe), systemic/LV haemodynamics, cardiac output (pulmonary artery flow) and load-independent LV inotropy/lusitropy via pressure-volume relationships. A continuous-flow LVAD (RotaFlow) device was used. Energetic components were determined before and during LVAD unloading, at both partial (50 % support, aortic valve opening) and complete (100 % uncoupling) support). These were compared with data obtained during partial inferior vena cava occlusion (IVCX, n=8) at matched level of volume unloading. Data were also collected when phenylephrine was administered to restore systemic haemodynamics (IVCX+PE) in order to mimic partial support.

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Results showed that partial LVAD support (57±4 % total cardiac output) preserved systemic/peak LV pressures (–3 ± 2 %) and cardiac output (–1±1 %), while decreasing LV preload (–13 ± 2 %), filling pressures (–29±7 %) and stroke volume (–28±5 %). Both the estimated LV chamber elastance (Ea; +40±11 %) and effective arterial elastance (Ees; +33±7 %) increased with support. The release of ANP was also reported during partial support. Despite marked reductions in SW (–29±5 %) and PVA (–31±4 %), there was a negligible change in MVO2 (+1±2 %). By contrast, complete support (109±9 %) decreased LV pressures (–33±10 %), normalised ANP release, and normalised Ea (–1±14 %) but not Ees (+54±12 %). There were further reductions in SW and PVA, with moderate MVO2 reductions (–13±4 %). Unsupported reductions in the preload (IVCX) decreased pressures. There was a decrease in MVO2 (–39±4 %), and PVA (–58±4 %). The Ea and Ees remained unchanged. Pressure support (CTRL+PE) increased Ea and blunted the MVO2 reductions (–7±2 %). Of interest, the LVAD support altered the MVO2 versus PVA relationship in the ventricles (see Figure 1).2

In conclusion, acute intra-cardiac LVAD support, particularly under partial unloading, can trigger mechano-energetic alterations, paradoxically hindering the ability of an LVAD to energetically unload the ventricle. There may be a limit to MVO2 reductions under LVAD support. Use of the LVAD engages intrinsic coupling mechanisms of the ventricles. Finally, an LVAD is, perhaps, perceived as a 'stress' signal, reflected in the release of ANP. On the basis of this research, Dr Del Rio said that there was a need for an increased understanding of the coupling and the mechanism that allows the heart to perceive the LVAD signal. This may allow us to pharmacologically inhibit this mechanism and increase the effectiveness of LVAD-mediated unloading on heart recovery. This should give us the beneficial effects of circulatory support as well as the potential for PVA reduction without a shift in the PVA/MVO2 relationship.

References

  1. Burkhoff D, Sayer G, Doshi D, et al. Hemodynamics of mechanical circulatory support. J Am Coll Cardiol 2015;66:2663–74.
    Crossref | PubMed
  2. Del Rio CL, Bennett S, Noel-Morgan J, et al. J Cardiovasc Transl Res 2017. In press.
Door to Unload in ST-segment elevation MI: Safety and Feasibility Study

Dr Meraj is an Interventional Cardiology Specialist at the Hofstra Northwell Health School of Medicine in New York.

Dr Meraj began his presentation with an overview on the current treatment paradigm in acute myocardial infarction (MI) with or without cardiogenic shock (CS), which focuses on primary perfusion in the first 2 hours. In acute coronary occlusion, time is of the essence, and the relationship between shorter door-to-balloon (DTB) times and improved outcomes is well established. Maximal benefit of reperfusion therapy is observed when the therapy is applied within 2 hours of the patient presenting at the hospital.1 This has led to the adoption of a target 90 minutes DTB time. However, the maximal effect of DTB time may have been reached. Recent data have indicated that while the average DTB has fallen well below 90 minutes, a corresponding drop in mortality rates of MI patients has not been observed.2 Additional strategies are therefore needed to reduce in-hospital mortality rates in this population.

Understanding the balance between myocardial oxygen supply and demand in MI has enabled us to develop effective left ventricle (LV) unloading protocols.3,4 Numerous preclinical investigations have supported the hypothesis that primary LV unloading and delaying coronary reperfusion provides both cardioprotective signalling and myocardial salvage. These scientific investigations have in part led to a recent paradigm shift in acute MI management that proposes door-tosupport time as an emerging target of therapy to reduce reperfusion injury and improve outcomes associated with MI/CS.5

In late 2016 the US Food and Drug Administration gave approval for the Door to Unloading (DTU) in ST-segment elevation MI (STEMI) safety and feasibility study. This study is a prospective feasibility study to evaluate the use of the Impella CP device for unloading of the LV prior to primary percutaneous coronary intervention (PPCI) in patients presenting with acute STEMI, without CS.6 The main inclusion criteria are age 21–80 years, first MI and acute anterior STEMI with ≥2 mm in two or more contiguous anterior leads or ≥4 mm total ST-segment deviation sum in the anterior leads, and presentation between 1 and 6 hours of symptom onset.

Patients are randomised to two treatment arms: immediate Impella implantation followed by 30 minutes of mechanical unloading prior to PPCI, or immediate Impella implantation directly followed by PPCI. The Impella is explanted after 3–4 hours of support. This time was chosen as the optimal unloading time is not known and the implications for leaving in a 14 Fr sheath for longer than 4 hours may have safety implications. The primary endpoints are the composite of cardiovascular mortality, re-infarction, stroke or transient ischaemic attack, major vascular complication at 30 days, and also an additional exploratory efficacy endpoint of the infarct size as percentage of LV mass, evaluated by cardiac magnetic resonance (CMR) at 30 days post- PPCI (see Figure 1).

The first patient was enrolled in April 2017. To date, all patients have met the <90 min DTB times, including those who had delayed reperfusion. The DTU metric will be determined for each patient as the study continues. We will need an understanding of 3- to 5-day and 30-day magnetic resonance imaging (MRI) to guide optimisation of infarct size reduction. Results from these patients will be used to guide best practices for the pivotal study. Given the design of the study and its time-sensitive nature, enrolment decisions are based only on the patient history taken at the time of initial presentation. It can be difficult to explain the treatment and precisely ascertain clinical symptom start time. A radial approach is used for access for the non-large bore site to reduce unnecessary vascular complications. Patient screening should also be considered to enable adequate MRI; some patients may be claustrophobic and unable to undergo the procedure, an unanticipated complication of the study design. Other clinical considerations include the completeness of revascularisation in STEMI, use of adjunctive pharmacotherapy during Impella support, duration of Impella support after PPCI, and access site management, i.e. removal of the pump using manual compression or pre-close suture.

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In summary, this ongoing study has a strong focus on safety, using large bore access and device therapy. Appropriate patient selection is key to help us to understand the physiology and clinical correlates to DTU and how to use concomitant therapies to improve patient outcomes.

References

  1. Cannon CP, Gibson CM, Lambrew CT, et al. Relationship of symptom-onset-to-balloon time and door-to-balloon time with mortality in patients undergoing angioplasty for acute myocardial infarction. JAMA 2000;283:2941–7.
    Crossref | PubMed
  2. Menees DS, Peterson ED, Wang Y, et al. Door-to-balloon time and mortality among patients undergoing primary PCI. N Engl J Med 2013;369:901–9.
    Crossref | PubMed
  3. Burkhoff D, Sayer G, Doshi D, et al. Hemodynamics of mechanical circulatory support. J Am Coll Cardiol 2015;66:2663–74.
    Crossref | PubMed
  4. Suga H, Hayashi T, Shirahata M. Ventricular systolic pressurevolume area as predictor of cardiac oxygen consumption. Am J Physiol 1981;240:H39–44.
    PubMed
  5. Esposito ML, Kapur NK. Acute mechanical circulatory support for cardiogenic shock: the “door to support” time. F1000Res 2017;6:737.
    Crossref | PubMed
  6. Door To Unloading With IMPELLA CP System in Acute Myocardial Infarction (DTU), https://clinicaltrials.gov/ct2/ show/NCT03000270 (accessed 5 October 2017.)
Ventricular Unloading and Inflammation – The Role of Impella in Myocarditis

Dr Tschöpe is a Professor of Medicine and Cardiology and the Vice Director of the Department of Cardiology, Charité, CVK, Berlin, guiding the cardiomyopathy programme. His main research interests are the potential of cell therapies to cure heart failure and the role of the immune system in heart failure.

Acute fulminant myocarditis and giant cell myocarditis have a poor prognosis.1 At present, short-term mechanical circulatory support (MCS) for myocarditis patients with refractory cardiogenic shock (CS) has predominantly used extracorporeal membrane oxygenation (ECMO),2 despite the use of Impella CP® for all other CS situations. Several case reports of successful short-term use of the Impella in fulminant myocarditis and giant cell myocarditis have been published.3–7

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These reports have suggested that peripheral unloading with the Impella may not be merely providing circulatory support, but it also may be conferring additional anti-inflammatory effects that modify the disease state, thus allowing a bridge to recovery in patients with fulminant myocarditis. In order to explore this hypothesis further, Dr Tschöpe presented the known pathophysiological processes underlying myocarditis, including pro-inflammatory and fibrotic processes that lead to cardiac remodelling and failure during disease progression. In an overloaded myocardium such as is present during fulminant myocarditis, mechanical stress activates integrins (mechanoreceptors) in the heart, which are known to mediate pro-inflammatory and fibrotic processes. Furthermore, integrins are known to have direct detrimental effects on the contractile apparatus. These combined effects exacerbate myocarditis, and contribute to the observed poor patient outcomes. Therefore, the hypothesis is logically raised whether haemodynamically unloading the heart by means of MCS (thereby decreasing mechanical stress) is a sufficient means to overcoming these pathophysiological mechanisms.

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The hypothesis that mechanical unloading may improve reverse remodelling in fulminant myocarditis was tested in a 62-yearold patient recently admitted to the practice of Dr Tschöpe with severe myocarditis and pre-CS despite immunosuppressive therapy. An axillary Impella 5.0 was implanted, which remained in place for 40 days. After 2 days in bed, the patient was mobile. Steroid therapy and unloading gave a significant improvement in ejection fraction from 5 days after implantation. In addition, the patient’s NT-pro brain natriuretic peptide levels reduced over time (see Figure 1), and increases were seen in EF and global longitudinal strain during short-time loading (see Figure 2). After 4 weeks, an echocardiogram showed the first signs of recovery.

Serial left ventricular biopsies taken at various time points during treatment to assess biomarkers of inflammation. These data demonstrate that the inflammatory response was significantly reduced during the time of Impella support. During this time steroids were also applied to decrease the inflammatory response. However, importantly, when the Impella was removed, the inflammatory response significantly increased, despite continued steroid use (see Figure 3). This suggests that Impella support may provide clinically important additional antiinflammatory benefits beyond that observed with steroids alone. This pattern was seen for the levels of adhesion molecules ICAM-1 and VCAM-1, and also integrin receptors. Mass spectroscopic analysis of the biopsy samples revealed significant changes in protein composition, notably in the matrix proteins collagen and vimentin, which are important for integrin function. There was also a rapid improvement in titin function after unloading, which is essential for maintaining the elasticity of cardiomyocytes. Finally, energy consumption was assessed by measurement of glucose uptake and mitochondrial malate dehydrogenase. Again, a significant improvement was seen during the period of mechanical unloading.8

In conclusion, experience to date supports the hypothesis that prolonged unloading with an Impella device offers circulatory support with additional disease-modifying effects that are important for bridging fulminant myocarditis patients to recovery.

References

  1. Cooper LT Jr, Berry GJ, Shabetai R. Idiopathic giant-cell myocarditis – natural history and treatment. Multicenter Giant Cell Myocarditis Study Group investigators, N Engl J Med 1997;336:1860–6.
    Crossref | PubMed
  2. den Uil CA, Akin S, Jewbali LS, et al. Short-term mechanical circulatory support as a bridge to durable left ventricular assist device implantation in refractory cardiogenic shock: a systematic review and meta-analysis. Eur J Cardiothorac Surg 2017;52:14–25.
    Crossref | PubMed
  3. Andrade JG, Al-Saloos H, Jeewa A, et al. Facilitated cardiac recovery in fulminant myocarditis: pediatric use of the Impella LP 5.0 pump. J Heart Lung Transplant 2010;29:96–7.
    Crossref | PubMed
  4. Fox H, Farr M, Horstkotte D, et al. Fulminant myocarditis managed by extracorporeal life support (Impella® CP): a rare case. Case Rep Cardiol 2017;2017:9231959.
    Crossref | PubMed
  5. Narain S, Paparcuri G, Fuhrman TM, et al. Novel combination of Impella and extra corporeal membrane oxygenation as a bridge to full recovery in fulminant myocarditis, Case Rep Crit Care 2012;2012:459296.
    Crossref | PubMed
  6. Suradi H, Breall JA. Successful use of the Impella device in giant cell myocarditis as a bridge to permanent left ventricular mechanical support. Tex Heart Inst J 2011;38:437– 40.
    PubMed
  7. Perry P, David E, Atkins B, et al. Novel application of a percutaneous left ventricular assist device as a bridge to transplant in a paediatric patient with severe heart failure due to viral myocarditis. Interact Cardiovasc Thorac Surg 2017;24:474–6.
    Crossref | PubMed
  8. Tschöpe C. J Cardiovasc Transl Res 2017. In press.
Clinical Data and Experience With a Novel Right Ventricular Support Device, the Impella RP

Mark Anderson is the vice chair of cardiac surgery services and a cardiothoracic surgeon in the Hackensack University Medical Group. He is a leading expert in minimally invasive heart surgery, robotic techniques and mechanical assist devices. Dr Anderson is a founding member of the A-CURE Working Group.

Dr Anderson began his presentation by highlighting the high incidence of right ventricular (RV) failure during clinical interventions, including implantation with ventricular support devices.1,2 The pathophysiology of RV failure includes impaired RV contractility, RV pressure overload, and RV volume overload.3 Univentricular RV failure does occur, though biventricular involvement is commonly seen. RV failure increases morbidity and mortality rates in all clinical settings. Early management of RV failure is essential to improve survival.

The Impella RP is a modified version of the Impella CP that is designed for right heart support. One important difference is that, rather than pulling blood, it pushes blood from the inferior vena cava to the pulmonary artery. The Impella RP has received approval from the US Food and Drug Administration (FDA).4 Approval was based on the findings of the RECOVER RIGHT study, which investigated the use of Impella RP support system in patients with RV failure (n=30).5 Each study had two cohorts: patients with RV failure after left ventricular assist device implantation and patients with RV failure after cardiotomy or myocardial infarction, with a duration of support of 3 to 4 days. Haemodynamic improvement was seen following Impella implantation. There was also a decrease in the use of inotropes and vasopressors in all patients after Impella RP support. The primary endpoint was defined as survival at 30 days post device explant or hospital discharge (whichever is longer). The overall survival rate at 30 days was 73.3 %. All patients discharged were alive at 180 days. This endpoint was reached in 77 % of patients. The rate of device-related bleeding and haemolysis was low.

A continuous access protocol with same inclusion/exclusion criteria as those in the RECOVER RIGHT study was set up to continue the RECOVER RIGHT study during the initial FDA application. In addition, the Impella RP® Post Approval Study, a prospective, single arm, multi-centre study monitoring the safety and outcomes trends of the Impella RP device in patients with RV failure who require haemodynamic support (n=26), was completed in the last year.

Dr Anderson discussed some unresolved clinical issues that have been identified during these studies, primarily the challenge in accurately predicting and sometimes diagnosing RV failure. He also mentioned that there are still several practices that need further refinement and standardisation, including the anticoagulation approach and weaning protocols.

In conclusion, RV failure is associated with increased mortality rates and is difficult to predict and sometimes to diagnose. The Impella RP device is easy to use and consistently improves patient haemodynamics while providing ventricular unloading. The Impella RP has a favourable safety profile with low adverse events across all studies. The use of Impella RP in RVF has demonstrated improved survival. The Impella RP therefore represents a viable tool to enable recovery or as a bridge to other destination therapies.

References

  1. Kormos RL, Teuteberg JJ, Pagani FD, et al. Right ventricular failure in patients with the HeartMate II continuous-flow left ventricular assist device: incidence, risk factors, and effect on outcomes. J Thorac Cardiovasc Surg 2010;139:1316–24.
    Crossref | PubMed
  2. McIlvennan CK, Magid KH, Ambardekar AV, et al. Clinical outcomes after continuous-flow left ventricular assist device: a systematic review. Circ Heart Fail 2014;7:1003–13.
    Crossref | PubMed
  3. Piazza G, Goldhaber SZ. The acutely decompensated right ventricle: pathways for diagnosis and management. Chest 2005;128:1836–52.
    Crossref | PubMed
  4. FDA, Impella RP: Summary of safety and probable benefit, https://http://www.accessdata.fda.gov/cdrh_docs/pdf14/ H140001B.pdf (accessed 5 October 2017).
  5. Anderson MB, Goldstein J, Milano C, et al. Benefits of a novel percutaneous ventricular assist device for right heart failure: The prospective RECOVER RIGHT study of the Impella RP device. J Heart Lung Transplant 2015;34:1549-60.
    Crossref | PubMed
Impella Support Improves Pulmonary Congestion in Cardiogenic Shock

Dr Westenfeld is head of the intensive care medicine and heart failure section at University Hospital, Dusseldorf, Germany. His research interests include the pathomechanisms of cardiovascular calcification, interventional treatment strategies in high-risk patients, and myocarditis and transplant rejection.

Dr Westenfeld began by describing the current state of understanding of pulmonary congestion in cardiogenic shock (CS). The evolution of systemic inflammatory response and multiple organ dysfunction syndrome following cardiopulmonary resuscitation may affect postcardiac- arrest-syndrome.1 Acute lung injury is an unrecognised problem in patients on extracorporeal life support (ECLS) who undergo implantation of a long-term mechanical circulatory support (MCS) device.2 In addition, early progression of pulmonary oedema (within 24 hours) has been found to predict mortality in patients with extracorporeal membrane oxygenation (ECMO).3 Increased pulmonary congestion in patients with ECMO carries the same mortality risk as dialysis. However, there have been no studies on the evolution of pulmonary congestion in CS.

Dr Westenfeld’s team proposed the hypothesis that that pulmonary congestion in CS develops differently according to the type of MCS (Impella versus intra-aortic balloon pump [IABP]), and also that early increase of pulmonary congestion in CS is associated with adverse outcome and recovery. In order to investigate this hypothesis, a method of quantifying pulmonary congestion without the use of a CT scan was required. The Halperin score identifies six areas from chest X-rays and assigns scores according to the observed opacification. Congestion is then classified according to the Halperin score as mild (score 100), moderate (230) or severe (310).

Dr Wentenfeld presented a retrospective study that identified 74 patients with CS who had received either IABP (January 2012– May 2015, n=43) or Impella (April 2014–June 2016, n=31) support.4 After excluding patients who died during the blanking period or those who required ECLS, 60 patients remained for analysis; 30 who received IABP and 30 who received the Impella. On admission, patient characteristics were similar between groups (see Table 1). They had high serum lactate during MCS support, which was higher in the Impella group (see Table 1). Similarly, troponin levels, inotropic score, and levels of lactate dehydrogenase were also high, but not significantly different between groups. Data suggest that the patients treated with Impella may have been associated with increased tissue perfusion, which could lead to the observed higher lactate levels, or this group may have included sicker patients, supported by the data that an upgrade to ECLS or left ventricular assist device was needed in 10 % of the IABP group versus 33 % in the Impella group (P=0.03). Pneumonia was reported in 76 % of patients receiving IABP and 56 % receiving the Impella (P=0.18). Hospitalisation in the intensive care unit was required for 15±15 days and 24±14 days in the IABP and Impella groups, respectively (P=0.03). Total hospitalisation was 30±35 days and 48±30 days, respectively (P=0.03). At 30 days, survival was 42 % and 48 %, respectively (P=0.8).

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Regarding the impact of ventricular unloading by the Impella on pulmonary congestion, a significant decrease in the Halperin score at 72 hours was observed in patients treated with Impella compared with those treated with IABP (see Figure 1). When the entire cohort was divided into patients who did or did not experience pulmonary decongestion as defined by the Halperin score, an association was seen between reduction of pulmonary congestion within the first 24 hours and improved survival in CS (see Figure 2). However, this Impella-dependent effect did not translate directly into a significant survival benefit in the overall cohort. Dr Westenfeld commented that in the cohort he examined, decongestion was achieved in 73 % of Impella-supported patients, but only 50 % of IABP patients.

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In conclusion, in this single centre study, data suggest that early progression of pulmonary oedema is associated with poor outcome in CS. Left ventricular unloading by Impella may more effectively facilitate pulmonary decongestion in CS compared with IABP support. This study was limited by its small sample size and retrospective design. There is a need for a large-scale analysis of outcomes and confounders in large registry studies. In addition, prospective analysis is needed of pulmonary congestion in CS, using early assessment by ultrasound, guiding escalation strategies, and investigating weaning and haemodynamics. Finally, mechanistic studies in large animal models will help elucidate the effects at the molecular level in terms of mitochondrial function, reactive oxygen species production and the effects of unloading on inflammation.

References

  1. Werdan K, Gielen S, Ebelt H, et al. Mechanical circulatory support in cardiogenic shock. Eur Heart J 2014;35:156–67.
    Crossref | PubMed
  2. Boulate D, Luyt CE, Pozzi M, et al. Acute lung injury after mechanical circulatory support implantation in patients on extracorporeal life support: an unrecognized problem. Eur J Cardiothorac Surg 2013;44:544–50.
    Crossref | PubMed
  3. Westenfeld R, Saeed D, Horn P, et al. Early progression of pulmonary edema predicts mortality in patients with extracorporeal life support. J Heart Lung Transplant 2014;33(Suppl):S251.
  4. Westenfeld R, et al. Impella support improves pulmonary congestion in cardiogenic shock. J Cardiovasc Transl Res 2017. In press.
Plenary Lecture: The Evolution of Cardiovascular Disease Worldwide: New Frontiers

Dr Fuster is a distinguished figure in the cardiology field. Following his graduation from the University of Edinburgh he commenced work at the Mayo Clinic and Mount Sinai, where he is now physician-in-chief. In 1996 he received the Principe de Asturias Award of Science and Technology, the highest award given to a Spanish-speaking scientist. In 2010 Dr Fuster received an Honoris Causa from the University of Edinburgh, one of the 40 that he has achieved to date. As of December 2016 Dr Fuster has served as Program Director for the American College of Cardiology’s Annual New York Cardiovascular Symposium for 22 consecutive years. He has also authored books and starred in a movie, The Resilient Heart, which focused on his work in prevention of cardiovascular disease (CVD). Dr Fuster is a member of the Institute of Medicine of the National Academy of Sciences.

The evolution of CVD therapy worldwide is moving towards identifying risk at early stages of life.1 While recent advances in surgery, intervention, pharmacology, imaging and genetics have been impressive for the treatment and understanding of later stage CVD; mechanisms of disease differ at different life stages. The 2013 American College of Cardiology Foundation/American Heart Association (ACCF/AHA) Guideline for the Management of Heart Failure (HF) guidelines was based on advanced disease.2 While recent work has highlighted the rapid advances that have been made in understanding dilated cardiomyopathy, a precursor to HF,3 and assist devices have proven effective in end-stage disease,4 Dr Fuster emphasised the need to focus on people at high risk for HF, but without structural heart disease.

He highlighted recent additions to the guidelines that have included biomarkers that may help identify an at-risk population.5 These include screening assays based on levels of pro-brain natriuretic peptide6 and troponin,7 leading to high-sensitivity cardiac troponin (hs-cTn) assays.8 Sixyear increases in the levels of hs-cTn, suggestive of progressive myocardial damage, are independently associated with HF.9 A risk model based on these biomarkers has been used to develop a robust tool for the prediction of cardiovascular death in patients with stable coronary heart disease.10 Other aspects of changing approaches to CVD include a greater focus on the atherosclerotic disease burden rather than on features of individual plaques,11 and the evolving paradigm of CVD as a systemic disease that is dependent on macrophage activity.12 Imaging studies of patients after acute coronary syndrome (ACS) have demonstrated increased splenic metabolic activity after ACS and its association with proinflammatory remodelling of circulating leukocytes.13 Evolving non-invasive technologies are also evaluating ischaemia at the microcirculation level.14 In the future, Dr Fuster predicts that ischaemia of each artery will be assessed by noninvasive techniques.

Dr Fuster turned his focus to the evolving landscape of CVD and what he believed the future hold for its various treatments. Due to the increasing prevalence of diabetes, Dr Fuster predicts an increasing use of coronary artery bypass grafts and decreasing use of optimal medical therapy and percutaneous intervention. However, pharmacology may play a role in earlier disease stages. Of particular interest are the proprotein convertase subtilisin/kexin 9 inhibitors,15 and the results emerging from cardiovascular outcome trials involving sodium-glucose cotransporter 2 inhibitors and glucagon-like peptide 1 analogues.16 In addition, new treatment modalities for HF that are employed at the early stages of the disease are emerging,17 and cardiovascular regenerative medicine using genetic editing is advancing rapidly and offers considerable future potential.18

Dr Fuster turned his attention to the challenges of treating HF in older patients. Chief among his concerns was patient adherence to therapy, which has led to the development of the polypill for cardiovascular prevention.19–21 Also important is the issue of cognitive degeneration due to microvascular disease. The cumulative burden of cardiovascular risk factors from childhood/adolescence has been associated with worse midlife cognitive performance independent of adulthood exposure.22 Dr Fuster is currently undertaking a study known as the Trans-Atlantic Network to Study Stepwise Noninvasive imaging as a Tool for Cardiovascular Prognosis and Prevention (TANSNIP) heart to heart (H2H), to investigate the relationship between levels of dementia and cardiovascular risk factors.

Finally, Dr Fuster emphasised that of all the risk factors for CVD, behaviour is the most difficult to modify. However, a number of successful community interventions have illustrated the value of education.25 Several studies and health programmes have independently indicated that behaviour modification, in terms of preventing CVD, is best achieved if the intervention is applied at early ages. Dr Fuster is personally involved in many educational initiatives that promote cardiovascular health during childhood.26 Dr Fuster concluded by reinforcing the importance of identifying CVD at an early stage.

References

  1. Fuster V. Stratified approach to health: integration of science and education at the right time for each individual. J Am Coll Cardiol 2015;66:1627–9.
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  2. Yancy CW, Jessup M, Bozkurt B, et al. 2013 ACCF/AHA guideline for the management of heart failure: a report of the American College of Cardiology Foundation/American Heart Association Task Force on practice guidelines. Circulation 2013;128:e240–327.
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  3. Weintraub RG, Semsarian C, Macdonald P. Dilated cardiomyopathy. Lancet 2017;390:400–14.
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  4. Rogers JG, Pagani FD, Tatooles AJ, et al. intrapericardial left ventricular assist device for advanced heart failure. N Engl J Med 2017;376:451–60.
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  5. Yancy CW, Jessup M, Bozkurt B, et al. 2017 ACC/AHA/HFSA Focused Update of the 2013 ACCF/AHA Guideline for the Management of Heart Failure. J Am Coll Cardiol 2017;70:776–803.
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  6. McKie PM, Burnett JC Jr. NT-proBNP: the gold standard biomarker in heart failure. J Am Coll Cardiol 2016;68:2437–9.
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  7. Westermann D, Neumann JT, Sorensen NA, et al. Highsensitivity assays for troponin in patients with cardiac disease. Nat Rev Cardiol 2017;14:472–83.
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  8. Twerenbold R, Boeddinghaus J, Nestelberger T, et al. Clinical use of high-sensitivity cardiac troponin in patients with suspected myocardial infarction. J Am Coll Cardiol 2017;70:996– 1012.
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  9. McEvoy JW, Chen Y, Ndumele CE, et al. Six-year change in high-sensitivity cardiac troponin t and risk of subsequent coronary heart disease, heart failure, and death. JAMA Cardiol 2016;1:519–28.
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  10. Lindholm D, Lindback J, Armstrong PW, et al. Biomarker-based risk model to predict cardiovascular mortality in patients with stable coronary disease. J Am Coll Cardiol 2017;70:813–26.
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  11. Arbab-Zadeh A, Fuster V. The myth of the “vulnerable plaque”: transitioning from a focus on individual lesions to atherosclerotic disease burden for coronary artery disease risk assessment. J Am Coll Cardiol 2015;65:846–55.
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  12. Libby P, Nahrendorf M, Swirski FK. Leukocytes link local and systemic inflammation in ischemic cardiovascular disease: an expanded “cardiovascular continuum”. J Am Coll Cardiol 2016;67:1091–103.
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  13. Emami H, Singh P, MacNabb M, et al. Splenic metabolic activity predicts risk of future cardiovascular events: demonstration of a cardiosplenic axis in humans. JACC Cardiovasc Imaging 2015;8:121–30.
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  14. Kato S, Saito N, Nakachi T, et al. Stress perfusion coronary flow reserve versus cardiac magnetic resonance for known or suspected CAD. J Am Coll Cardiol 2017;70:869–79.
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  15. Lloyd-Jones DM, Morris PB, Ballantyne CM, et al. 2017 Focused update of the 2016 ACC expert consensus decision pathway on the role of non-statin therapies for ldl-cholesterol lowering in the management of atherosclerotic cardiovascular disease risk. J Am Coll Cardiol 2017;70:1785–822.
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  16. Sattar N, Petrie MC, Zinman B, et al. Novel diabetes drugs and the cardiovascular specialist. J Am Coll Cardiol 2017;69:2646–56.
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  17. von Lueder TG, Krum H. New medical therapies for heart failure. Nat Rev Cardiol 2015;12:730–40.
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  18. Climent AM, Sanz-Ruiz R, Fernández-Santos ME, et al. General overview of the 13th TECAM conference: time for a global initiative in 2016. Circ Res 2016;119:409–13.
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  19. Sanz G, Fuster V, Guzmán L, et al. The fixed-dose combination drug for secondary cardiovascular prevention project: improving equitable access and adherence to secondary cardiovascular prevention with a fixed-dose combination drug. Study design and objectives. Am Heart J 2011;162:811–7 e1.
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  20. Castellano JM, Sanz G, Penalvo JL, et al. A polypill strategy to improve adherence: results from the FOCUS project. J Am Coll Cardiol 2014;64:2071–82.
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  21. Yusuf S, Lonn E, Pais P, et al. Blood-pressure and cholesterol lowering in persons without cardiovascular disease. N Engl J Med 2016;374:2032–43.
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  22. Rovio SP, Pahkala K, Nevalainen J, et al. Cardiovascular risk factors from childhood and midlife cognitive performance: the young Finns study. J Am Coll Cardiol 2017;69:2279–89.
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  23. Baber U, Mehran R, Sartori S, et al. Prevalence, impact, and predictive value of detecting subclinical coronary and carotid atherosclerosis in asymptomatic adults: the BioImage study. J Am Coll Cardiol 2015;65:1065–74.
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  24. Khera AV, Emdin CA, Drake I, et al. Genetic risk, adherence to a healthy lifestyle, and coronary disease. N Engl J Med 2016;375:2349–58.
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  25. Gómez-Pardo E, Fernández-Alvira JM, Vilanova M, et al. A comprehensive lifestyle peer group-based intervention on cardiovascular risk factors: the randomized controlled Fifty- Fifty program. J Am Coll Cardiol 2016;67:476–85.
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  26. Bansilal S, Vedanthan R, Kovacic JC, et al. Rationale and design of family-based approach in a minority community integrating systems-biology for promotion of health (FAMILIA), Am Heart J 2017;187:170–81.
    Crossref | PubMed
Left Ventricular Support Using Impella Relieves Left Arterial Stretch and Inhibits Atrial Arrhythmias Through Reduced Oxidative Stress

Dr Ishikawa is an assistant professor at Icahn School of Medicine at Mount Sinai, New York.

Dr Ishikawa's talk focused on his investigations into how left ventricular mechanical support affects left atrial haemodynamics. He recalled the common observation that following implantation of an Impella CP into the ventricle of a porcine model of myocardial infarction (MI), a dramatic reduction in left ventricular end diastolic pressure (LVEDP) is immediately seen. As flow is gradually increased, a further decrease in LVEDP follows. This led Dr Ishikawa to question how the unloading of the left ventricle would affect left atrium (LA) physiology, as the latter is closely linked to LVEDP. He investigated this by placing a pressurevolume catheter inside the LA through an atrial septostomy, and recording the effects of LV mechanical on atrial haemodynamics. In the same porcine model of MI, he observed a flow-dependent unloading of the LA (see Figure 1).1 A characteristic LA-PV loop was seen (see Figure 2), in which the left side of the loop represents atrial contraction, giving rise to atrial pressure and a simultaneous decrease in volume as blood is expelled. When the mitral valve (MV) closes, the LA relaxes and we can observe the passive filling phase of the chamber by blood flow from the pulmonary veins. When the LA is stiff, the slope of the pressure–volume relationship is steeper because the same amount of volume increase will lead to a higher increase in pressure. This slope may, therefore, be considered as an index of LA stiffness. In patients with cardiac disease leading to a less compliant myocardium, steeper slopes are observed (see Figure 2).

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Dr Ishikawa compared the slopes of these atrial pressure-volume loops in the same pigs before and after Impella LV support. The steepness of the slope, and therefore LA stiffness, was significantly decreased after LV Impella support. During MI, LVEDP increases together with LA pressure. This stretches the LA, making it more difficult to expand. Dr Ishikawa highlighted the interdependence of LA haemodynamics on those of the LV. The observed reduction in LVEDP while on Impella supported correlated well with the LA pressure as well as maximal LA volume (see Figure 3). In terms of LA function, LA ejection fraction was improved when the Impella was supporting the LV. Importantly, this was not associated with an increased atrial load, indicated by reduction of LA atrial work and developed pressure (dp/dt max) when the Impella was in place.1 This suggested that atrial contraction was more efficient when the atrium was unloaded.

Since atrial stretch is a known mechanism for atrial arrhythmia, Dr Ishikawa’s team investigated whether the use of the Impella reduced arrhythmogenesis. Using pacing of the right atrium, atrial tachycardia or atrial fibrillation was induced in the majority (70 %), while not unloaded by the Impella. By supporting these same pigs with an Impella in the LV, the rate of atrial arrhythmia was reduced to only 30 % (see Figure 4). Furthermore, the duration of the arrhythmia events was found to correlate with the maximum LA volume, suggesting that LA stretch may play a key role in mediating the maintenance of atrial arrhythmias.1

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Dr Ishikawa’s team then explored the molecular mechanism underlying this effect. Earlier research found that stretching cardiomyocytes in vitro induces oxidative stress and increases spontaneous Ca2+ leak from the sarcoplasmic reticulum, which is a demonstrated arrhythmogenic trigger.2 Dr Ishikawa’s team therefore measured the expression level of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2), a stretch-dependent source of reactive oxygen species. He found levels of NOX2 to be increased in the LA after MI compared with controls, but NOX2 levels were remained unaffected in those animals that underwent LV Impella support for 2 hours. He demonstrated that increased NOX2 levels were associated with increased phosphorylation the ryanodine receptor 2, the source of diastolic Ca2+ leak. This increased phosphorylation was not observed in atria supported with the Impella.

In conclusion, LV unloading with the Impella CP also significantly affects the haemodynamics of the upstream LA. Directly unloading the LV with mechanical support leads to passive unloading of the LA, reduces LA stretch, and inhibits atrial arrhythmogenesis by modulating stretch-dependent oxidative stress.

References

  1. Ishikawa K, Watanabe S, Bikou O, et al. J Cardiovasc Transl Res 2017. In press.
  2. Prosser BL, Ward CW, Lederer WJ. X-ROS signaling: rapid mechano-chemo transduction in heart. Science 2011;333:1440–5.
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Utilisation of Support Device Hysteresis to Track Cardiac Function

Dr Edelman is the Thomas D and Virginia W Cabot Professor of Health Sciences and Technology at MIT, Professor of Medicine at Harvard Medical School, and Senior Attending Physician in the coronary care unit at the Brigham and Women’s Hospital in Boston. His team has pioneered basic findings in vascular biology and the development and assessment of biotechnology. Dr Edelman directs the Harvard-MIT Biomedical Engineering Center, dedicated to applying the rigors of the physical sciences to elucidate fundamental biological processes and mechanisms of disease. Dr Edelman is a founding member of the A-CURE Working Group.

Dr Edelman commenced his presentation by reminding the audience that the Impella can be utilised not only as a therapeutic tool, but also as a diagnostic tool. Since it resides in the ventricle, it is uniquely positioned to provide insights into the function of the heart. It works in concert with the heart, is relatively non-disruptive, and its design allows the extraction of a substantial amount of information. The pump maintains a constant rotor speed by changing the motor current in response to the variable load caused by a pulsatile flow envirwonment. The motor current undergoes subtle variations in every beat. Dr Edelman’s team therefore proposed the hypothesis that the relationship between a pump parameter (motor current) and a physiological parameter (pressure head) could be used to obtain diagnostic information on the function of the left ventricle (LV). The plotted relationship between the pressure head and the motor current forms a hysteresis loop which is asymmetric, non-linear and changes with each cycle, making extraction of information challenging. However, every pump exhibits the same hysteresis loop phases, making it possible to extract information about heart function such as the LV end diastolic pressure (LVEDP), peak pressure, slope of relaxation and slope of contraction.

In a recent study that aimed to validate this hypothesis, an Impella CP with both ventricular and aortic pressure sensors was implanted into a mock circulation loop.1 The contractility was kept constant and the LVEDP was varied (see Figure 1). Similarly, it was possible to maintain a constant preload and vary the contractility. The motor current and aortic pressure were extracted from the console and plotted to illustrate the hysteresis relationship (see Figure 1). These inputs were then used to calculate LVEDP and contractility measurements. Using these techniques, multiple indices of LV function may be measured. Dr Edelman presented a flow chart describing the method for the use of device extracted metrics to predict physiological function, such as LVEDP during (see Figure 2).1 It is hoped that this approach to estimating metrics of heart function will be placed into next generation of Impella devices.

Swan-Ganz catheters are used in patients regularly to estimation of LVEDP with real-time wedge tracing during end-expiratory hold. This new method of estimating heart function using device derived metrics would decrease the number of catheters in patients on Impella support by having one catheter residing in the LV that provides both circulatory support and heart function information.

In summary, understanding the dynamic changes of disease progression and its effect on cardiac state allows for standardised care of the patient, as well as improved outcomes using quantitative optimisation. From the clinician point of view, it also allows determination of the optimal Impella therapy in conjunction with other forms of therapy.

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References

  1. Chang BY, Keller SP, Feng KY, et al. Utilization of support device hysteresis to track cardiac function. J Cardiovasc Transl Res 2017. In press.
Optimal Haemodynamic Support during Cardiac arrest in the Cardiac Catheterisation Laboratory

Kapil Lotun is Associate Professor of Medicine, Associate Director Cardiac Cath Lab, Director of TAVR Program, Director of Vascular Medicine, Director of Structural Heart Disease, Sarver Heart Center, Division of Cardiology, University of Arizona, USA.

The goals of therapy for cardiac arrest in the catheterisation laboratory are to maintain vital end organ perfusion and correct the precipitating cause of cardiac arrest, usually achieved by percutaneous coronary intervention (PCI). However, these goals often compete with each other. Manual chest compression is very challenging in the catheterisation laboratory, partly because of space limitations, and can result in the provider experiencing excessive radiation exposure. Mechanical cardiopulmonary resuscitation (CPR) provides unique advantages over manual chest compression for treating cardiac arrest in the cardiac catheterisation laboratory.1

Mechanical circulatory support (MCS) has the potential to provide adequate end organ perfusion in this situation. It is readily available and can be initiated quickly. The available MCS devices have low complication rates and are inexpensive. Of the available devices, the TandemHeart is not practical to implant during cardiac arrest. Use of the Impella or extracorporeal membrane oxygenation (ECMO), however, hold more potential (see Table 1). A recent study found that the use of MCS during resuscitation of cardiac arrest in the catheterisation laboratory increases the rate of return of spontaneous circulation (ROSC).2 A case series (n=8) found that use of the Impella was feasible in selected patients with cardiac arrest and gave a 6-month survival rate of 50 %.3 The same survival rate was reported in a case series (n=14) that employed miniaturised ECMO systems.4

Recently, Dr Lotun’s team conducted a study in which 30 pigs were randomly assigned to interrupted manual chest compressions (n=10) versus either a piston chest compression device (LUCAS™; n=10) or a percutaneously inserted Impella device (n=10), supporting systemic haemodynamics and perfusion during two clinically relevant time periods of cardiac arrest associated with a left main/proximal left anterior descending (LAD) coronary occlusion in the cardiac catheterisation laboratory.5 The primary endpoint was favourable neurological function of survivors at 24 hours. Secondary endpoints included defibrillation success, ROSC and resuscitation-generated haemodynamics. The primary endpoint was achieved in 29 % of the LUCAS group and 33 % of the Impella group compared with none of the manual group.5 ROSC was achieved in 78 % of the Impella group, compared with 50 % and 59 % in the manual and LUCAS groups, respectively.

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In conclusion, cardiac arrest in the catheterisation laboratory is a devastating event and will be more common with increasingly complex interventional procedures. The goal of circulatory support is to provide vital organ perfusion while the operator is correcting the underlying cause. Mechanical compression devices offer unique advantages over manual compression in this setting. The placement of percutaneous MCS devices can be considered but further studies are needed to define the optimal device and clinical outcomes.

References

  1. Chang BY, Keller SP, Feng KY, et al. Utilization of support device hysteresis to track cardiac function. J Cardiovasc Transl Res 2017. In press.
  1. William P, Rao P, Kanakadandi UB, et al. Mechanical cardiopulmonary resuscitation in and on the way to the cardiac catheterization laboratory. Circ J 2016;80:1292–9.
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  2. Venturini JM, Retzer E, Estrada JR, et al. Mechanical chest compressions improve rate of return of spontaneous circulation and allow for initiation of percutaneous circulatory support during cardiac arrest in the cardiac catheterization laboratory. Resuscitation 2017;115:56–60.
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  3. Vase H, Christensen S, Christiansen A, et al. The Impella CP device for acute mechanical circulatory support in refractory cardiac arrest. Resuscitation 2017;112:70–4.
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  4. Arlt M, Philipp A, Voelkel S, et al. Early experiences with miniaturized extracorporeal life-support in the catheterization laboratory. Eur J Cardiothorac Surg 2012;42:858–63.
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  5. Truong HT, Lotun K, Kern KB, et al. Poster presented at the American Heart Association Annual Meeting 2016.
Myocardial Mitochondrial Reactive Oxygen Species Production is Reduced in the Left Ventricle of Mechanically Unloaded Hearts

Dr. Scheiber is a practicing cardiac physician at Heinrich Heine Universität Düsseldorf. He was the recipient of the Young Investigator Scholarship for the 2017 A-CURE Symposium.

Dr Scheiber was the recipient of the Young Investigator Scholarship Award. He commenced his presentation with a discussion of mitochondrial energy metabolism in the failing heart. The heart consumes more energy than any other organ. To match this high energy demand, myocardial mitochondria cycle up to 6 kg of ATP every day, which is about 20 to 30 times the heart’s own weight. Myocardial mitochondrial energy metabolism in the failing heart has, therefore, become a field of considerable interest.1,2

Increased ventricular filling pressure and volume are hallmarks of heart failure (HF) pathophysiology.3,4 This pressure and volume overload is linked to alterations in myocardial substrate utilisation, mitochondrial energy production, and mitochondrial reactive oxygen species formation.5,6 Clinical evidence suggests that ventricular unloading can reverse systemic and local metabolic dysfunction in patients with advanced HF treated with durable ventricular assist devices.7 However, there are no functional data on mitochondrial respiration in the failing heart under these unloading conditions.

Dr Scheiber’s team proposed the idea that chronic left ventricular unloading in terminal patients with HF would improve myocardial mitochondrial oxidative phosphorylation and reduce myocardial mitochondrial reactive oxygen species production. In order to investigate this hypothesis, a prospective study evaluated 13 patients undergoing heart transplantation between October 2016 and July 2017. Eight patients had a left ventricular assist device (LVAD) surgically implanted as a 'bridge to transplant' prior to heart transplantation. Myocardial tissue specimens were harvested from macroscopically scar-free areas of the left ventricular free wall of the explanted heart. Patients did not differ significantly in age or body mass index. The average time of unloading in the LVAD-supported patients was 20 months.

The ex vivo maximal myocardial oxidative phosphorylation capacity was analysed in tissue specimens. There was a similar maximum oxygen flux on fatty acids and tricarboxylic acid cycle derivates in chronically unloaded compared with standard heart explants. Interestingly, the respiratory control ratio, which is a surrogate marker of coupling efficiency, was significantly increased in the unloaded group compared with the standard transplant group, suggesting more efficient ATP production in these mitochondria. Analysis of myocardial mitochondrial hydrogen peroxide production between these two groups showed that reactive oxygen species production during mitochondrial respiration was decreased in tissue samples of the chronic unloaded hearts (see Figure 1).

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In conclusion, this study found an increased mitochondrial coupling efficiency and decreased hydrogen peroxide production in chronically unloaded hearts, but no differences in maximal mitochondrial respiration when comparing those hearts haemodynamically unloaded by LVADs with hearts that were unsupported. Future research will investigate whether alterations of mitochondrial respiration occur during ventricular unloading in acute cardiogenic shock and, if so, how this may impact patient outcomes and heart recovery. Other planned studies include the impact of acute ventricular unloading on mitochondrial respiration and hydrogen peroxide production.

References

  1. Bayeva M, Gheorghiade M, Ardehali H. Mitochondria as a therapeutic target in heart failure. J Am Coll Cardiol 2013;61:599–610.
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  2. Stride N, Larsen S, Hey-Mogensen M, et al. Decreased mitochondrial oxidative phosphorylation capacity in the human heart with left ventricular systolic dysfunction, Eur J Heart Fail 2013;15:150–7.
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  3. Ponikowski P, Voors AA, Anker SD, et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J 2016;37:2129–200.
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  4. Miller WL. Fluid volume overload and congestion in heart failure: time to reconsider pathophysiology and how volume is assessed. Circ Heart Fail 2016;9:e002922.
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  5. Neubauer S. The failing heart – an engine out of fuel. N Engl J Med 2007;356:1140–51.
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  6. Sawyer DB, Siwik DA, Xiao L, et al. Role of oxidative stress in myocardial hypertrophy and failure. J Mol Cell Cardiol 2002;34:379–88.
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  7. Chokshi A, Drosatos K, Cheema FH, et al. Ventricular assist device implantation corrects myocardial lipotoxicity, reverses insulin resistance, and normalizes cardiac metabolism in patients with advanced heart failure. Circulation 2012;125:2844–53.
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  8. Scheiber D, et al. J Cardiovasc Transl Res 2017. On press.
Combining Extracorporeal Membrane Oxygenation and Impella for the Treatment of Cardiogenic Shock

Dr Westermann is Deputy Director of the Department of General and Interventional Cardiology, University Heart Centre Hamburg. He is a specialist in Internal Medicine and Cardiology.

Dr Westermann opened his talk by reminding the audience of the surprising findings of the intraaortic balloon pump (IABP) SHOCK II study, which showed that the use of an IABP did not significantly reduce 30-day mortality in patients with cardiogenic shock (CS) complicating acute myocardial infarction.1 Alternative methods of treating CS have, therefore, been sought. Many doctors have turned to using extracorporeal membrane oxygenation (ECMO) to support these patients. Dr Westermann presented unpublished data from a large study (n=9,258) that showed a rapid growth in the use of ECMO in Germany from 2007–2014.2 Survival at 30 days was lower in patients over 65 years old and in those who required cardiopulmonary resuscitation (CPR). Using these data, an ECMO mortality score has been developed and validated.2 However, prolonged use of ECMO (>2 days) is associated with greatly increased mortality.3 The use of ECMO presents a number of clinical challenges. In particular, Dr Westermann highlighted that ECMO leads to an increased ventricular afterload. This increased afterload can become pathophysiological in ECMO patients causing vascular complications (bleeding, ischaemia, embolism), increased left ventricular (LV) filling pressures, increased in LV wall stress, pulmonary congestion, and the watershed phenomenon. The solution to this pathophysiological haemodynamic derangement is to vent the ECMO patient and relieve increased LV pressures and volume.

Recently, Dr Westermann’s team has investigated a different LV venting strategy in ECMO patients. The addition of VA-ECMO leads to decreased stroke volume and a right-shift of the pressure-volume loop. This increased afterload is due to retrograde femoral flow in CS. This causes further ECMO-dependent increases in LV wall stress and LV pressures, conditions that are unfavourable to the patient. Therefore, there is a need to shift pressure-volume loops to the left, which can be achieved by unloading the LV. This can be achieved through transseptal methods (e.g. atrioseptostomy, TandemHeart) or the less invasive transvalvular route (e.g. Impella). Dr Westermann suggested that the use of the Impella in addition to VA-ECMO may improve outcomes in patients with CS due to LV unloading.

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This hypothesis was tested in a study that enrolled 157 patients with CS: 123 received VA-ECMO support and 34 had concomitant treatment with VA-ECMO and an Impella device. A propensity-matching analysis was performed in a 2:1 ratio, comparing 42 patients undergoing VA-ECMO alone (control group) with 21 patients treated with VA-ECMO and Impella. Patients in the VA-ECMO plus Impella group (termed Ecmella) had a significantly lower rate of in-hospital mortality (47 % versus 80 %; P<0.001) and a higher rate of successful bridging to either recovery or further therapy (68 % versus 28 %; P<0.001) compared with patients receiving VA-ECMO alone.4 Similar findings have been observed in Dr Westermann’s recent registry study in Hamburg (n=81).5 There is increased haemolysis in the Ecmella group, but he indicated this did not lead to increased clinical complications. Those patients treated with ECMO/Ecmella also had significantly more rapid weaning from inotropes.

In conclusion, ECMO therapy may improve survival in CS; however, there is a lack of randomised controlled trial data. In addition, haemodynamic challenges remain with ECMO therapy in CS, including increases in afterload, LV wall stress, and pulmonary congestion. LV unloading with concomitant use of an Impella device may positively affect outcomes in patients with CS on VA-ECMO. It should be noted that data in support of this new concept have been derived from a registry study. Randomised controlled trial data are required. Nevertheless, Dr Westermann’s group have decided to use the Ecmella strategy as their clinical standard for future ECMO patients.

References

  1. Thiele H, Zeymer U, Neumann FJ, et al. Intraaortic balloon support for myocardial infarction with cardiogenic shock. N Engl J Med 2012;367:1287–96.
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  2. Becher PM, Westermann D. Unpublished data.
  3. Chang CH, Chen HC, Caffrey JL, et al. Survival analysis after extracorporeal membrane oxygenation in critically ill adults: a nationwide cohort study. Circulation 2016;133:2423–33.
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  4. Pappalardo F, Schulte C, Pieri M, et al. Concomitant implantation of Impella® on top of veno-arterial extracorporeal membrane oxygenation may improve survival of patients with cardiogenic shock. Eur J Heart Fail 2017;19:404–12.
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  5. Westerman D. Unpublished data.
Concluding Remarks

In the closing remarks, Dr Kapur commented that the work presented has provided a huge breadth of research related to acute unloading and myocardial recovery, acknowledging the support of the sponsorship from Abiomed. Dr Anderson commented that this meeting represents an advance from last year and exciting and inspiring to see new thoughts and investigations that will further advance the field. He made special reference to Dr Fuster, whose passion for the cardiovascular field has driven him to accomplish so much. Dr Anderson hopes that passion for this new field of cardiology will encourage investigators to think outside the box. Dr Burkhoff concluded the meeting by acknowledging the quality of the presentations and posters, which is unprecedented in an emerging field. While he recognised the unique advantages of being a small group in a unique setting, he encouraged future growth of the A-CURE group.