Mechanical Circulatory Support for AMI and Cardiogenic Shock

Abstract

Cardiogenic shock following acute myocardial infarction affects 5% to 10% of patients and carries a grave prognosis. The dismal prognosis associated with post-MI cardiogenic shock, allied with surgical and technological advancements, has shifted the treatment paradigm toward wider use of mechanical circulatory support devices (MCSD). Current experience demonstrates that better outcomes may be achieved with early MCSD deployment (prior to the onset of end-organ dysfunction). However, perceived limitations with existing devices mean that they remain infrequently applied. There is an urgent need for increased awareness of MCSD options among clinicians treating post-MI shock patients.

Short-Term Mechanical Management of Cardiogenic Shock

“…Proper functioning of the balloon pump requires a stable intrinsic cardiac rhythm; thus, the IABP cannot augment blood flow adequately in patients with tachycardia or arrhythmias. More importantly, IABP support requires a certain level of residual left ventricular function and, therefore, is frequently ineffective in patients with severe MI [1] or even cardiac arrest [4]. Additionally, in many cases, the hemodynamic support derived from an IABP is not efficient enough to reverse CS [8].…”

“…Presystolic deflation of the balloon reduces afterload and augments diastolic blood pressure and coronary perfusion. The net effect is an improved myocardial oxygen supply and reduced demand through a reduction in myocardial work, as well as an approximate 1.5-L/min increase in cardiac output [1,4]. & Currently, the joint American College of Cardiology/American Heart Association guidelines recommend the early use of IABP support to stabilize patients with CS [1], but IABPs have several limitations.…”

“…The net effect is an improved myocardial oxygen supply and reduced demand through a reduction in myocardial work, as well as an approximate 1.5-L/min increase in cardiac output [1,4]. & Currently, the joint American College of Cardiology/American Heart Association guidelines recommend the early use of IABP support to stabilize patients with CS [1], but IABPs have several limitations. Proper functioning of the balloon pump requires a stable intrinsic cardiac rhythm; thus, the IABP cannot augment blood flow adequately in patients with tachycardia or arrhythmias.…”

“…This condition is associated with in-hospital mortality rates of 50-80%. The most common cause of CS is acute myocardial infarction (AMI), and 5-10% of AMI patients develop CS [1]. The incidence of CS in the Global Utilization of Streptokinase and Tissue Plasminogen Activator (TPA) for Occluded Coronary Arteries (GUSTO-I) trial was 7.2%, and CS was associated with an overall in-hospital mortality of 56% and a 1-year mortality of 80% [2], making AMI complicated by CS the leading cause of in-hospital death for patients admitted with acute coronary syndromes [3].…”

“…The aim of MCS in CS is to restore cardiac output and end-organ perfusion by off-loading the left ventricle to optimize the balance between myocardial oxygen supply and demand, allowing ischemic but viable myocardium to recover [1]. Current expert guidelines support intra-aortic balloon pump (IABP) counterpulsation as the method of choice for mechanical assistance in CS [3, 7•], but there are other options that have demonstrated an impressive ability to rapidly reverse the hemodynamic derangements of CS.…”