Impact of Microaxillar Mechanical Ventricular Support on Renal Resistive Index in Patients with Cardiogenic Shock after MI

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Dr Schieffer began by stating that his institution adopted a regionalised system of care in 2013, along the lines of the National Cardiogenic Shock Initiative.1 The results of this initiative showed that networking improves patient outcomes. His institution also established one of the first cardiac arrest centres in Germany. As part of this initiative, 2,117 patients with out-of-hospital cardiac arrest between January 2013 and August 2019 were medically transported over a distance (range 23–97 km) and admitted to their institution. The overall survival was about 45% at 6 months and about 42% at 12 months. Among the 426 patients with post-cardiac arrest cardiogenic shock (CS) receiving Impella, the initiation of support pre-percutaneous coronary intervention (PCI) resulted in lower levels of lactate and lower vasoactive scores over 6–72 hours than post-PCI support. In addition, Impella support pre-PCI was associated with higher survival, a greater increase in left ventricular ejection fraction at 72 hours after support initiation and lower levels of creatinine (indicative of end-organ function).

Based on the above results, Dr Schieffer’s team investigated whether Impella improves renal perfusion in CS. The renal resistive index (RRI) has been studied to gain diagnostic and prognostic insights into a variety of renal pathologies (such as the progression of chronic kidney disease and renal allograft rejection), but also for the prediction of renal outcomes in critically ill patients.2,3 Therefore, Dr Schieffer’s team evaluated if RRI, determined by intrarenal artery Doppler measurements, can serve as an indicator of haemodynamics during Impella support.

RRI, measured as the quotient of (peak systolic velocity − end-diastolic velocity)/peak systolic velocity, was obtained in 15 patients with CS supported with an Impella between May and October 2018 using Doppler ultrasound.4 Simultaneously, blood pressure was determined invasively in the radial artery. RRI was determined in both kidneys in 13 patients and one kidney in two patients. The mean difference between right and left RRI was 0.026 ± 0.023 (p=0.72). When the Impella support was increased by a mean of 0.44 l/min (± 0.2 l/min), the systolic or diastolic blood pressure remained unchanged, whereas RRI decreased significantly from 0.66 ± 0.08 to 0.62 ± 0.06 (p<0.001) consistently in all patients, implying normalisation of renal perfusion.

This observation is consistent with the notion that Impella support may promote renal protection by enhancing renal perfusion. The RRI measurement serves as an early, easy and fast method for monitoring kidney function. The early detection of kidney hypoperfusion aids in prompt initiation of therapeutic manoeuvres, which are not possible when using alternative markers of acute kidney injury, such as low urine output or serum creatinine levels.

In closing, Dr Schieffer mentioned two ongoing studies investigating RRI-guided Impella treatment in high-risk PCI and CS due to acute MI.


  1. Tehrani BN, Truesdell AG, Sherwood MW et al. Standardized team-based care for cardiogenic shock. J Am Coll Cardiol 2019;73:1659–69.
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  2. Radermacher J, Chavan A, Bleck J, et al. Use of Doppler ultrasonography to predict the outcome of therapy for renal-artery stenosis. N Engl J Med 2001;344:410–7.
    Crossref PubMed
  3. Le Dorze M, Bouglé A, Deruddre S, et al. Renal Doppler ultrasound: a new tool to assess renal perfusion in critical illness. Shock 2012;37:360–5.
    Crossref PubMed
  4. Markus B, Patsalis N, Chatzis G et al. Impact of microaxillar mechanical left ventricular support on renal resistive index in patients with cardiogenic shock after myocardial infarction. Eur Heart J Acute Cardiovasc Care 2019; epub ahead of press.
    Crossref PubMed