Article

Haemodynamic Support Devices for Complex and High-risk Percutaneous Coronary Intervention

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Abstract

Patients at high risk, such as those with marked left ventricular dysfunction, acute coronary syndromes with unstable haemodynamics and arrhythmias, as well as single target vessels that supply a large area of myocardium, are undergoing percutaneous coronary intervention (PCI) with increasing frequency. Percutaneous haemodynamic support devices, including intra-aortic balloon counterpulsation pumps, percutaneous cardiopulmonary support and left ventricular assist devices, have been developed as adjunctive therapies during these complex procedures. Improvements in haemodynamic profiles with the use of these devices enhance procedural safety, allowing successful PCI to be performed in a more stable environment. Nevertheless, the use of these devices is associated with potentially serious complications and solid evidence for their routine use in high-risk PCI is lacking. Ongoing improvements in device designs and deployment techniques may eventually allow earlier, prophylactic use of support devices. Until then, the use of haemodynamic support devices should be individualised after careful consideration of the potential benefits and risks involved.

Keywords

Percutaneous coronary intervention (PCI), percutaneous haemodynamic support, cardiogenic shock,

Disclosure:Vladimír Džavík receives partial funding from the Brompton Funds Professorship in Interventional Cardiology and has received speaker's honoraria from Abiomed Inc. Kay Woon Ho has no conflicts of interest to declare.

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DOI:https://doi.org/10.15420/ecr.2012.5.1.17

Correspondence Details:Vladimír Džavík, Interventional Cardiology Program, Peter Munk Cardiac Centre, University Health Network, 6-246 EN Toronto General Hospital, 200 Elizabeth Street, Toronto, Ontario, Canada, M5G 2C4. E: vlad.dzavik@uhn.on.ca

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Techniques and devices used in percutaneous coronary intervention (PCI) have evolved significantly since the inception of the procedure. Procedural and patient outcomes have improved, while more complex coronary lesions in high-risk patients are being attempted with increasing frequency. High-risk procedures are carried out in patients with marked left ventricular dysfunction, acute coronary syndromes – often with unstable haemodynamics and cardiac arrhythmias – as well as single target vessels that are survivaldependent or supply a large area of myocardium. Haemodynamic compensatory mechanisms are often extremely limited in such patients and transient ischaemia during PCI can rapidly lead to a downward spiral of haemodynamic collapse and death. Unsurprisingly, intervention in these high-risk situations often demands the prophylactic use of circulatory support devices. The use of intracoronary stents in the majority of PCI cases has dramatically reduced the incidence of abrupt closure and flow-limiting dissections. As a result, the focus of circulatory support during PCI has shifted from the maintenance of coronary perfusion, using techniques such as anterograde coronary perfusion or coronary sinus retroperfusion, to systemic haemodynamic stabilisation with mechanical support devices.1,2 Indications for haemodynamic support devices have expanded from support during haemodynamic collapse to include prophylactic insertion for high-risk PCI. Percutaneous haemodynamic support devices can be classified into three major types, namely, the intra-aortic balloon counterpulsation pump (IABP), percutaneous cardiopulmonary support (CPS) and left ventricular assist devices (VADs). The limitations and benefits of each device are summarised in Table 1. Evidence of their use in acute myocardial infarction (AMI)/emergent PCI and in elective high-risk PCI will be reviewed in detail.

Intra-aortic Balloon Counterpulsation

The concept of using counterpulsation to support the failing heart was first described by Harken in 1958.3 In 1962, Moulopoulos developed the counterpulsation principle and described the use of a single-chambered intra-aortic balloon positioned in the descending thoracic aorta.4 The balloon inflation begins with closure of the aortic valve until the onset of ventricular systole, when the balloon is rapidly deflated. Inflation of the balloon during diastole was postulated to augment coronary perfusion by displacing intra-aortic blood towards the coronary tree. Decreased pressure caused by deflation of the balloon results in reduced afterload and, consequently, less left ventricular work (see Figures 1 and 2). Six years later, Kantrowitz described the first clinical experience with IABP in patients in cardiogenic shock.5 Continued advancement in IABP technology over the years has led to expanded clinical applications and adoption of its use worldwide. A review of the IABP utility has revealed haemodynamic support during or after cardiac catheterisation as the most common clinical indication.6

Widespread availability in the modern cardiac catheterisation laboratory, familiarity with the device, its relatively low cost and ease of insertion are key advantages of the IABP. In addition to this, haemolysis is minimal, as is the need for monitoring or technical support, with improvements in automated algorithms to detect changes in the patient or environmental conditions and optimal setting adjustment by the newer IABP consoles. Limitations of the IABP include the need for stable cardiac rhythm and output for its use as well as only modest augmentation of cardiac output. Contraindications to IABP insertion include significant aortic regurgitation, aortic dissection or aneurysm, bleeding diathesis, uncontrolled sepsis and severe peripheral vascular disease. Data from the Benchmark registry showed overall major complications to be low, at 2.6%.6 The incidence of major limb ischaemia was 0.9%, balloon leak 1.0%, severe bleeding 0.8% and in-hospital mortality related to IABP was 0.05%. Female gender, old age and peripheral vascular disease were independent predictors of a serious complication. The rate of unsuccessful IABP deployment was low (2.3%), with the majority of cases being due to balloon leaks, poor inflation, poor augmentation or difficulty of insertion.

Use in Acute Myocardial Infarction/Emergent Percutaneous Coronary Intervention

Clinical application of the IABP in AMI was investigated in several studies. One multicentre randomised trial evaluated the effects of IABP compared to standard management to sustain infarct-related artery patency after successful reperfusion with PCI within 24 hours of AMI.7 The use of IABP was associated with significantly lower reocclusion (8% versus 21%, p<0.03) and composite clinical endpoint of death, stroke, reinfarction, need for emergency revascularisation or recurrent ischaemia (13% versus 24%, p<0.04) than standard management. Conflicting findings were found in a similar randomised study where prophylactic IABP usage following primary PCI did not significantly reduce infarct-related artery reocclusion, reinfarction, myocardial recovery or mortality. IABP was in fact associated with a higher incidence of stroke (2.4% versus 0%, p=0.03).8 In a meta-analysis of IABP use in ST elevation AMI, IABP was found not to confer significant survival benefits or improvement in left ventricular ejection fraction (LVEF), and was associated with higher stroke and bleeding rates (see Figures 3 and 4). In a separate meta-analysis of cohort studies investigating ST elevation myocardial infarction (STEMI) in patients with cardiogenic shock with primary PCI, IABP was associated with a 6% (95% confidence interval: 3–10%; p=0.0008) increase in 30-day mortality. This was in contrast to an absolute decrease in 30-day mortality of 18% with adjunctive IABP use in a thrombolysis study (Figure 5).9 Hence, routine IABP support of PCI in STEMI patients is not evidence based.

The ongoing Counterpulsation reduces infarct size pre-PCI for AMI (CRISP-AMI) trial is a multicentre, randomised, controlled study that aims to determine the effect of IABP before mechanical reperfusion on infarct size, post-PCI cardiovascular function and major adverse cardiac events up to six months. Eligible patients with ST elevation of the anterior leads scheduled for PCI within six hours from onset of AMI symptoms are randomised to receive either IABP or standard of care without IABP. The CRISP-AMI trial, in contrast to prior trials where the IABP is deployed after PCI, will shed light on the strategy of prophylactic IABP use prior to PCI in anterior MI.10

Use in High-risk, Non-emergent Percutaneous Coronary Intervention

Until recently, studies of IABP use in high-risk PCI other than AMI were small and non-randomised. Their results have suggested benefits of IABP support in patients with poor left ventricular function,11–13 abrupt vessel closure,14,15 hypotension11,14 and unprotected left main PCI, especially in the setting of impaired left ventricular function or intervention of the distal bifurcation.16 A recently published prospective, multicentre, randomised-controlled trial examined the use of IABP in 301 high-risk patients undergoing elective PCI.17 High risk was defined as the presence of impaired left ventricular function (LVEF <30%) with a large amount of myocardium subtended by the target vessels, characterised by:

  • a jeopardy score of eight or greater;
  • left main stenosis; or
  • a target vessel providing collateral supply to an occluded second vessel that in turn supplies >40% of the myocardium.

One hundred and fifty-one patients were randomised to receive elective IABP support that was initiated prior to PCI, while 150 were randomised to no IABP. There were no significant differences in major adverse cardiac and cardiovascular events (15.2% versus 16.0%, p=0.85) or all-cause mortality (4.6 versus 7.4%, p=0.32).17 Major or minor bleeding occurred in 19.2% and 11.3% (p=0.06; odds ratio: 1.86; 95% CI: 0.93–3.79) and access site complications in 3.3% and 0% (p=0.06) of the elective and no planned IABP groups, respectively.17 Major procedural complications (including prolonged hypotension, ventricular tachycardia/fibrillation requiring defibrillation or cardiorespiratory arrest requiring assisted ventilation) occurred more often in the no IABP group (10.7% versus 1.3%; p=0.001).17 This was driven mainly by prolonged procedural hypotension in 13 patients in the no IABP group. The use of IABP in high-risk PCI can either be prophylactic or as standby when haemodynamic instability occurs. A study of 68 consecutive patients who underwent high-risk PCI with prophylactic IABP support were compared with those of 46 patients who required rescue IABP. High-risk patients analysed included those with an acute coronary syndrome with clinical congestive heart failure, LVEF of <30%, multivessel disease, a left main or saphenous vein graft PCI target vessel, and pulmonary capillary wedge pressure >15mmHg and/or mean pulmonary artery pressure >50mmHg.18 Patients with cardiogenic shock or acute STEMI and those who were on mechanical ventilators were excluded. Procedural success was higher in the prophylactic group, with lower in-hospital mortality and major complications, compared to the rescue group. At six months, the mortality and major adverse cardiac event rates were lower in the prophylactic group (8% versus 29% [p<0.01] and 12% versus 32% [p=0.02], respectively).18 Prophylactic IABP insertion was the only independent predictor of survival at six months. The incidence of vascular complications was low and comparable, except for more major bleeding (15% versus 3%; p=0.03) in the rescue group.18 In summary, the evidence does not show clear clinical benefits. It shows the possible harm of routine IABP use in STEMI PCI or non-emergent, high-risk PCI. Routine use of IABP in these settings should be discouraged unless further studies show benefits.

Percutaneous Cardiopulmonary Support

In contrast to IABP, which requires stable cardiac rhythm and modestly augments existing cardiac output, CPS provides full support even during cardiac arrest and haemodynamically unstable arrhythmias. The development of percutaneously inserted thin-wall, large-bore catheters has allowed for the initiation of CPS without direct surgical cannulation of the right atrium and aorta, required in traditional cardiopulmonary bypass.19,20 Percutaneous initiation of CPS requires femoral venous and arterial access, followed by progressive dilation of the vessels to allow placement of 18–20Fr cannulae at the inferior vena cava–right atrial junction and distal descending aorta.21 After heparinisation, the cannulae are attached to a portable CPS system (CR Bard). Venous blood is pumped through a heat exchanger and membrane oxygenator, driven by a centrifugal pump and returned to the arterial system via the arterial cannula. Flow rates of 4–6l/min can be obtained and complete cardiopulmonary bypass achieved. Insertion of CPS cannulae and set up is, however, technically more demanding compared to IABP. There is considerable delay between initiation and achievement of full support, as well as the need for continuous, highly technical support and monitoring by skilled perfusionists. With the insertion and passage of stiff, large-bore cannulae, the most common complications are local vascular and neurological. Data from initial experiences with CPS from a national registry showed these local complications to be common (25%).22 With improvements in techniques, major complications have been dramatically reduced to 1.5%. Overall hospital mortality rate was 7.6%, with half of the deaths occurring in patients >75 years of age and those with left main disease.23

Use in Acute Myocardial Infarction/Emergent Percutaneous Coronary Intervention

Reports of CPS deployment in AMI patients are confined to patients with critical haemodynamic profiles, including those with cardiogenic shock, unstable cardiac arrhythmias or after out-of-hospital cardiac arrest during AMI undergoing emergency PCI.24–29

Nagao et al. conducted a prospective study to evaluate the use of emergency CPS in PCI of AMI patients who presented with refractory ventricular fibrillation.28 Thirty-two patients with AMI who had ventricular fibrillation that persisted despite advanced cardiac life support, including unsynchronised electric shock at least six times, were included. Nineteen patients presented with out-of-hospital arrest and 13 with refractory ventricular fibrillation after admission to the hospital. With full CPS support, successful PCI was performed in 29 patients (90.6%), with return of spontaneous circulation in 28 patients (87.5%). Despite the high rate of successful PCIs with CPS, 29 patients died during the acute hospitalisation. In a retrospective study, 24 patients with cardiogenic shock secondary to AMI received CPS support prior to cardiac catheterisation and PCI.29 Complete revascularisation was achieved in 12 patients (50%), with seven patients reverting to stable haemodynamic profiles after successful PCI. Seventeen patients remained in cardiogenic shock after PCI, however, requiring inotropic drug support. Two patients required IABP support. Three patients stabilised in 24 to 48 hours, while 14 patients (58%) died in hospital. Two patients (8%) had groin complications related to IABP insertion. The remaining 10 patients (42%) survived the acute hospitalisation and were discharged within 22 days.

Use in High-risk, Non-emergent Percutaneous Coronary Intervention

Several studies have demonstrated the feasibility of CPS in high-risk PCI.20–23 The national CPS registry evaluated 105 high-risk PCI patients with reduced LVEF of <25%, a target vessel supplying more than half the myocardium, or both.22 The use of CPS was associated with infrequent chest pain and electrocardiographic changes despite prolonged balloon inflations. The angioplasty success rate was 95%. A subsequent report demonstrated durable benefits of CPS-supported angioplasty, with one- and two-year survival rates (free of cardiac death) of 83% and 77%, respectively. Event-free survival for one and two years was 76% and 69.5% respectively.23

Considering factors of morbidity with CPS insertion and delay in CPS set up, prophylactic versus standby CPS for high-risk PCI was evaluated in a study of 569 patients.30 In this study, the standby approach involved placement of 5Fr sheaths in the contralateral femoral vein and artery, and cardiopulmonary system priming. Patients undergoing angioplasty with CPS were only initiated if there was irreversible haemodynamic compromise. These measures allowed full cardiopulmonary bypass to be initiated within a few minutes if haemodynamic collapse occurred. Thirteen of 98 patients in the standby group had irreversible haemodynamic compromise requiring CPS. CPS was successfully initiated within five minutes in 12 of these patients. Procedural success and major complications were similar between the two groups. Significantly more patients in the prophylactic group (42%) had local access site complication or needed blood transfusion compared to the standby group (11.7%; p<0.01). In the subset with LVEF<20%, mortality was higher in the standby group (4.8% versus 18.8%; p<0.05). This study suggested standby CPS to be an adequate strategy in most patients, but in those with LVEF<20%, prophylactic CPS use was shown to be preferred.

Evidence of the use of CPS in AMI and high-risk PCI has been drawn from small trials and registry data. In the emergent settings, patients generally had catastrophic haemodynamic profiles or were in extremis. Haemodynamic support with CPS facilitated completion of PCI and stabilised patients acutely. Despite this, mortality in the emergent PCI remains high, in keeping with the unfavourable presentations. In elective high-risk PCI, CPS support was feasible and again facilitated PCI completion. Due to the complexity of use and the relatively short period of time that the device could be deployed before onset of significant haemolysis, however, this technology has fallen out of favour.

Left Ventricular Assist Devices

A left VAD provides considerable systemic flow independent of a patient’s intrinsic cardiac rhythm or output. Of the various left VADs available, two designs – the percutaneous transeptal ventricular assist device and the axial flow pump – have developed into practical percutaneous haemodynamic support devices for use in the cardiac catheterisation laboratory and will form the focus of the following discussion.

Percutaneous Transeptal Ventricular Assist Devices

The TandemHeart (Cardiac Assist) system epitomises the percutaneous transeptal ventricular assist devices. Its design has evolved from the CPS system, where partial left heart bypass is achieved with the percutaneous transeptal placement of a 21Fr cannula into the left atrium. Oxygen-rich blood is pumped from the left atrium and returned to the systemic circulation via a 15Fr arterial cannula percutaneously inserted into the femoral artery, with the distal end lying above the aortic bifurcation (see Figure 6).31 TandemHeart technology eliminates the need for an oxygenator, which is used in the CPS system. It is driven by a centrifugal external pump capable of producing a non-pulsatile flow rate of 5lmin in the cardiovascular laboratory. The additional need for transeptal puncture increases the complexity of the procedure compared to other haemodynamic support devices, especially in emergent situations. Other limitations include not infrequent vascular access complications32 and iatrogenic atrial septal defects.33

Use of TandemHeart in Acute Myocardial Infarction/Emergent Percutaneous Coronary Intervention

A multicentre randomised trial compared use of the TandemHeart with IABP in the treatment of cardiogenic shock in 42 patients, 26 of these cases being secondary to AMI. Compared to patients on IABP support, patients who received TandemHeart support had significantly improved haemodynamic parameters with:

  • 20% higher cardiac index (95% CI: -5.8–46.1; p=0.13);
  • 18% higher mean arterial pressure (95% CI: -7.1–43.6; p=0.16); and
  • 18.5% lower pulmonary capillary wedge pressure (95% CI: -41.9–4.8; p=0.12).

Overall 30-day survival and incidence of adverse events were not significantly different between the two groups. There was one instance of TandemHeart failure, while another TandemHeart device had to be removed due to blood clotting in the cannula. The most common complications for the TandemHeart group included arrhythmias (57.9%), bleeding (42.1%), neurological dysfunction (31.6%), distal leg ischaemia (21.1%) and sepsis (21.1%). No specific adverse events were related to transseptal puncture and cannulation.34

In another randomised study, Thiele et al. evaluated TandemHeart compared to IABP use in patients with revascularised AMI complicated by cardiogenic shock. Although haemodynamic and metabolic parameters were significantly improved with TandemHeart compared to IABP, there were no differences in 30-day mortality (IABP 45% versus TandemHeart 43%, p=0.86). Complications such as severe bleeding and limb ischaemia were more common in the TandemHeart group.32

A recent study by Kar et al. evaluated the emergent use of TandemHeart support in 117 patients with severe refractory cardiogenic shock, defined as a systolic blood pressure of <90mmHg, a cardiac index of <2.0L/min/m2 and evidence of end-organ failure despite IABP/pressor support. Eighty patients had ischaemic and 37 patients had non-ischaemic aetiology. Mean duration of support was 5.8 ± 4.8 days. TandemHeart support resulted in a significant improvement in cardiac index, from a median of 0.52 to 3.0l/min/m2, as well as improvement in systolic blood pressure, mixed venous oxygen saturation, urine output, pulmonary capillary wedge pressure, lactic acidosis and creatinine levels. Complications included one wire-mediated perforation of the left atrium requiring emergent surgical repair, subsequent death due to post-operative complications and one case of a right common femoral artery dissection requiring surgical repair. Groin haematoma occurred in six patients (5.1%) and bleeding at the cannula site in 34 patients (29.1%). Other complications included:

  • coagulopathy (11%);
  • gastrointestinal bleeding (19.7%);
  • limb ischaemia (3.4%);
  • sepsis (29.9%); and
  • stroke (6.8%).

The 30-day mortality rate was 40.2%, which was lower despite worse baseline patient haemodynamic status compared to that observed in the Should we emergently revascularize occluded coronaries for cardiogenic shock (SHOCK) trial (47%).35 A meta-analysis of percutaneous left VAD versus IABP in cardiogenic shock that included two Tandem Heart trials32,34 and an Impella trial36 demonstrated superior haemodynamic support with left VAD use compared with IABP. This was shown by greater improvements in cardiac indexes, mean arterial pressures and lower pulmonary capillary wedge pressures.37 This did not translate into improved 30-day mortality (see Figure 7). Complication rates were higher in the VAD group (see Figure 8).

Use of TandemHeart in High-risk, Non-emergent Percutaneous Coronary Intervention

The use of the TandemHeart device in high-risk PCI in patients with unprotected left main artery stenting38 and severely compromised LVEF39,40 were evaluated in small non-randomised studies. Aragon et al. performed high-risk PCI on eight patients with the above-mentioned high-risk features. The patients were considered to be at exceptionally high risk for decompensation due to procedural complexity combined with underlying left ventricular dysfunction. Mean LVEF of the study population was 30%. Seven patients underwent multivessel PCI, including three with PCI of an unprotected left main artery. Procedural success was 100%. TandemHeart devices were removed immediately post-PCI with no recorded groin complications. One patient died 10 days after lower extremity bypass surgery, while another developed acute renal failure requiring haemodialysis post PCI. The remaining patients were symptom and event free during a mean follow-up period of 189 ± 130 days.40 To date, there are no convincing clinical data to suggest improved clinical outcome using TandemHeart compared to IABP in cardiogenic shock patients, despite superior haemodynamic support. The feasibility of TandemHeart support in highrisk PCI is suggested by small studies, but again clinical benefits have yet to be firmly established. More evidence is needed to demonstrate improved patient outcome before recommendations can be made for TandemHeart selection over the IABP in high-risk PCI in the emergent setting or otherwise.

Axial Flow Pumps

Axial flow pumps have adopted the principle of an Archimedes screw, whereby blood is pumped by a rotating turbine from the left ventricle via the inflow across the aortic valve into the ascending aorta. The earliest clinically available axial flow pump was the Hemopump (Medtronic).41 This device was introduced in the late 1980s and generated non-pulsatile flow rates of 3–4l/min, reducing left ventricular volume and augmenting systemic circulation. It had a large profile (21Fr), requiring placement in the left ventricle via a surgical insertion in the femoral artery.

The Hemopump has been superseded by the Impella device (Abiomed). The currently available Impella 2.5 and 5.0 devices are capable of pumping up to 2.5l/min or 5.0l/min of blood from the left ventricle into the ascending aorta. The Impella 2.5 is a 12Fr device that can be inserted percutaneously through the femoral artery (13F sheath) utilising a modified monorail technique under direct fluoroscopic control, across the aortic valve into the left ventricle. The Impella uses both a pressure lumen adjacent to the motor, as well as motor current monitoring for correct positioning verification. The tip of the device is an atraumatic pigtail that rests in the left ventricle (see Figure 7). In contrast, the Impella 5.0 is a 21Fr device and requires a surgical cutdown of the femoral artery for insertion.42 Compared to the IABP, superior haemodynamic support is provided by the Impella, independent of intrinsic cardiac rhythm and output.36 Myocardial ischaemic protection is achieved by simultaneous reduction of left ventricular workload and end-diastolic pressure, with extrusion of oxygenated blood from the left ventricular cavity into the aortic root and increased perfusion through the coronary ostium.43,44 Insertion of the Impella, especially the 2.5 version, is technically straightforward and reduces the complexity of set-up and support maintenance. Contraindications to Impella use include moderate to severe aortic insufficiency or aortic valve stenosis, a mechanical aortic valve or heart constrictive device and severe peripheral arterial disease.

Use of Impella in High-risk, Non-emergent Percutaneous Coronary Intervention

Studies to date have suggested the safety and reliability of the Impella, with low rates of implant or device failure and complications.45–47 In the Prospective feasibility trial investigating the use of the Impella Recover LP 2.5 system in patients undergoing high-risk PCI (PROTECT I), 20 patients who underwent high-risk PCI with an Impella 2.5 support were followed prospectively. All patients had LVEF <35% and underwent PCI on an unprotected left main artery or last patent coronary conduit. The Impella device was successfully deployed in all study patients. None of the patients developed haemodynamic compromise during PCI. At 30 days, two patients had died and two had a periprocedural myocardial infarction. Two patients developed mild, transient haemolysis without clinical sequelae. There were no cases of cardiac perforation, vascular injury or limb ischaemia, although one patient developed a groin haematoma requiring transfusion.48

The Europella registry evaluated 144 patients undergoing high-risk PCI with Impella 2.5 support.49 High-risk features included PCI of the left main artery PCI (52.8%) or last patent vessel (17.4%), multivessel disease (81.9%) and low LVEF (35.4%). Mortality at 30 days was 5.5%. Rates of myocardial infarction, stroke, bleeding requiring transfusion/surgery, and vascular complications at 30 days were 0%, 0.7%, 6.2% and 4.0%, respectively.49 Interim results of the USPELLA registry, detailing the use of Impella 2.5 in North America, were presented at Transcatheter Cardiovascular Therapeutics in 2010. There were 352 patients recruited from 24 centres. Indications for Impella deployment included high-risk urgent PCI (37%), high-risk elective PCI (29%), AMI with cardiogenic shock (20%) and other forms of shock (14%). High-risk features for elective PCI included LVEF <35%, an unprotected left main artery or last patent coronary artery PCI (52%), and multivessel PCI (88%). Mean support time was 60 minutes, with an average pump flow of 2.2 ± 0.2l/min. There was significant improvement in mean LVEF by 17% and improvement in the New York Heart Association classification by one or more categories in 52% of patients after Impella-supported PCI. Overall, the major adverse cardiovascular event rate was low, at 8%, and the 30-day survival rate was 96%.50 A prospective, multicentre, randomised controlled trial of the Impella recover LP 2.5 system versus IABP in patients undergoing non-emergent high-risk PCI (PROTECT II) trial was initiated in October 2007 to evaluate the comparative use of the Impella and IABP in non-emergent high risk PCI.51 In December 2010, after analysis of the outcomes by the Data and Safety Monitoring Board of the first 305 patients enrolled, the trial was halted for futility to reach the primary end-point of one-month adverse events. Further analyses are ongoing and the final results will be presented later this year.

Use of the Impella in Acute Myocardial Infarction/Emergent Percutaneous Coronary Intervention

The Efficacy study of left ventricular assist device to treat patients with cardiogenic shock (ISAR-SHOCK) trial compared the use of IABP and Impella in 26 AMI patients with cardiogenic shock.36 The use of Impella was found to be safe and provided better haemodynamic support compared to IABP. The increase in cardiac index at 30 minutes was significantly greater in Impella patients than in patients with IABP (+0.49 ± 0.46l/min/m2 versus +0.11 ± 0.31L/min/m2; p=0.02). The mean arterial pressure increased in patients with Impella LP 2.5 by 9.0 ± 14.0mmHg versus -1.2 ± 16.2mmHg in the IABP group (p=0.09). Improved haemodynamics did not translate into any signal to suggest improved clinical outcome, however, with 30-day mortality being 46% in both groups. Again, this was a small study and not powered to detect differences in mortality. Nonetheless, the lack of a signal of improved outcome with the device dictates that if it is to be utilised clinically, which it is in the US (see the USPELLA Registry), further adequately-powered trials are needed. Unfortunately, the only such trial to be launched – the Trial using Impella LP 2.5 System in patients with acute myocardial infarction-induced hemodynamic instability (RECOVER II) – was terminated in May 2010 after only one patient had been enrolled since July 2008.52

Decisions on Haemodynamic Support During High-risk Percutaneous Coronary Intervention

With the increasing availability of haemodynamic devices in the cardiac catheterisation laboratory, important considerations must be taken into account. These include which patient would benefit from use of these devices, which device would produce the most appropriate support needed and whether such devices should be used in a prophylactic manner or as standby support.

The decision as to whether to even consider the use of a haemodynamic support device is based on the interplay of patient and coronary anatomical factors. Clearly, haemodynamic instability or frequent haemodynamically-compromising arrhythmias should prompt early support device deployment, even before PCI, in an attempt to stabilise the clinical situation. Other considerations include factors that lower patients’ threshold for ischaemia and additional contrast load. These factors include:

  • markedly depressed LVEF, especially with decompensated, symptomatic heart failure; and
  • PCI on a single coronary artery that supplies a large area of viable myocardium, e.g. PCI on the last remaining patent vessel or on an unprotected left main artery in a left dominant system, in anticipation of intraprocedural haemodynamic compromise.

The amount of myocardium at risk of ischaemia can be estimated with ischaemic testing or by applying the Duke myocardium jeopardy score53 or Balloon pump-assisted coronary intervention (BCIS-1) study jeopardy score54 on the coronary anatomy. In the BCIS-1 trial, a jeopardy score of eight or more was arbitrarily used to identify significantly large myocardium at risk of ischaemia as high-risk PCI for IABP support.17 Subgroup analysis showed a non-significant trend towards event reduction with IABP use in patients with a high BCIS score of 12, compared to a neutral effect in those with a BCIS score of eight. No specific cut-off of the jeopardy score is available to identify patients who will benefit from haemodynamic support during high-risk PCI, although it would appear that patients with a higher score would benefit more than those with low scores. When deciding which of the available support devices to use, factors to consider include:

  • ease/speed of insertion;
  • anticipated complications with device usage;
  • adequacy of flow rates generated by the device;
  • cost;
  • availability of resources for technical monitoring;
  • maintenance post device insertion; and
  • stability of a patient’s intrinsic cardiac output or rhythm for proper device augmentation (IABP).

An ideal device would be one that is rapid, easy and safe to set up. It should provide adequate haemodynamic support, both in elective high-risk and emergent situations. Cardiac output produced should be physiological in terms of pulsatile flow, offloading of the left ventricle and adequate supply of oxygenated blood to all systemic organs, particularly the coronary arteries and myocardium. In addition, there should be minimal need for anticoagulation, negligible trauma to blood components and automated technical monitoring/maintenance post-deployment. The available devices have advantages and limitations, as detailed previously. An understanding of considerations will help the interventionalist make an informed decision on haemodynamic support device usage. In current clinical practice, ease of use, cost, availability and familiarity with the IABP will see continued use of this device as first-line therapy in many complex PCI cases requiring haemodynamic support. When superior haemodynamic support is needed, percutaneous left VAD will play an increasingly important role, especially with refinement of device design and deployment techniques. Left VAD haemodynamic superiority will need to be translated into improved clinical outcomes in adequately powered randomised trials.

Conclusion

Extensive improvements have been made to haemodynamic support devices over the past decades. These improvements have allowed for more extensive use of these devices, with considerably less morbidity. Ongoing clinical trials will provide insights into the comparative advantages and disadvantages of these devices in different clinical situations and guide daily clinical decisions.

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