Unloading in cardiogenic shock: the rationale and current evidence

Purpose of review Discussing the rationale and current evidence for left ventricular unloading in cardiogenic shock. Recent findings Microaxial flow pumps (MFP) and intra-aortic balloon pumps (IABP) augment cardiac output while simultaneously unloading the left ventricle (e.g. reducing left ventricular pressure), thereby targeting a key mechanism of cardiogenic shock. A recent randomized trial has shown a mortality reduction with MFP in selected patients with cardiogenic shock, strengthening the rationale for this strategy, although the evidence for the IABP is so far neutral. MFP/IABP can also be used concomitantly with veno-arterial extracorporeal membrane oxygenation (va-ECMO) to alleviate the va-ECMO-related increase in left ventricular afterload, to facilitate weaning and ultimately to improve myocardial recovery and prognosis of affected patients. However, the use of MFP/IABP in this indication solely relies on retrospective data, which need to be interpreted with caution, especially as these strategies are associated with more complications. Currently ongoing randomized trials will help to further clarify the role of left ventricular unloading in patients on va-ECMO. Summary Left ventricular unloading addresses a key mechanism of cardiogenic shock, with strong evidence to support MFP use in selected patients, but further randomized controlled trials are required to clarify the role of different devices/strategies for the overall shock population.