Mechanical Circulatory Support Devices in Acute Myocardial Infarction-Cardiogenic Shock: Current Studies and Future Directions

Abstract

Cardiogenic shock (CS) caused by acute myocardial infarction (AMI) accounts for most deaths in the population with AMI and continues to be associated with high short-term mortality. Several temporary mechanical circulatory support (MCS) devices have been developed to treat CS and studied in randomized controlled trials (RCTs) of patients with AMI-CS. Unfortunately, none of these RCTs has demonstrated an improvement in survival with temporary MCS in AMI-CS. Potential reasons for these negative results in RCTs are numerous and reflect the challenges of enrolling critically ill patients with CS. Researchers have used observational study designs to provide insights about outcomes associated with the use of temporary MCS in AMI-CS. These observational studies have yielded conflicting results, in some cases contrary to the results of RCTs. Several limitations pertinent to both RCTs and observational analyses, mostly relating to selection bias and failure to consider unmeasured confounding variables and population heterogeneity, preclude drawing strong inferences regarding the effects of temporary MCS on survival in populations with AMI-CS. Understanding these limitations is essential to correctly interpreting the literature regarding temporary MCS to treat AMI-CS and is necessary to inform the design of future studies that will potentially provide stronger evidence. Optimally matching temporary MCS devices to the needs of individual patients with AMI-CS will presumably be more successful than indiscriminate application in unselected patients. In this review, we discuss the existing literature on temporary MCS to treat AMI-CS and describe the specific challenges that must be overcome to develop an improved evidence base for guiding clinical practice.

Keywords: acute myocardial infarction; cardiogenic shock; extracorporeal membrane oxygenator; intra-aortic balloon pump; mechanical circulatory support; ventricular assist device.

Graphical abstract

Figure 1

Updated SCAI SHOCK classification schema. Reproduced with permission from Naidu et al. AMI, acute myocardial infarction; CS, cardiogenic shock; HF, heart failure; SCAI, Society for Cardiovascular Angiography & Interventions.

Figure 2

SCAI SHOCK Classification 3-axis model for conceptualization of patients with CS. Reproduced with permission from Naidu et al. CS, cardiogenic shock; LV, left ventricle; RV, right ventricle; SCAI, Society for Cardiovascular Angiography & Interventions.

Central Illustration

Potential reasons why published RCTs of temporary MCS in AMI-CS have not demonstrated significant differences in mortality. AMI-CS, acute myocardial infarction related cardiogenic shock; MCS, mechanical circulatory support; RCT, randomized controlled trial.

Figure 3

Kaplan-Meier curves demonstrating long-term mortality in patients with AMI-CS who were randomized to IABP vs medical therapy in the IABP-SHOCK-II trial. Reproduced with permission from Thiele et al. AMI, acute myocardial infarction; CS, cardiogenic shock; IABP, intra-aortic balloon pump.

Figure 4

Utilization of temporary MCS and mortality for patients with CS in centers participating in the Critical Care Cardiology Trails Network (CCCTN) based on the presence of an institutional shock team. ∗Advanced MCS includes percutaneous LVADs and ECMO. Reproduced with permission from Papolos et al. CICU, critical intensive care unit; CS, cardiogenic shock; MCS, mechanical circulatory support; PAC, pulmonary artery catheter.

Figure 5

Variability in the use of temporary MCS devices for AMI-CS in the United States Nationwide Inpatient Sample in 2014. MCS ratio denotes proportion of AMI-CS hospitalizations using temporary MCS. Reproduced with permission from Strom et al. AMI, acute myocardial infarction; CS, cardiogenic shock; MCS, mechanical circulatory support.