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.