Composite Trends of Cardiogenic Shock Complicating Acute Myocardial Infarction

Abstract

This article refers to ‘Trends in cardiogenic shock complicating acute myocardial infarction’ by N. Aissaoui et al., published in this issue on pages 664–672. Cardiogenic shock (CS) is the leading cause of death in patients with acute myocardial infarction (AMI), with in-hospital mortality as high as 40–50%.1-12 Although improved AMI care had significantly reduced the incidence of CS in the early 2000s, more recent observational studies showed varying trends with a decreased, stable or even slightly increased (usually when administrative datasets are used) incidence of CS, currently ranging from 3% to 15% of AMI cases (Figure 1).1-12 These conflicting data and the wide ranges might reflect differences in definitions and patient profiles, since CS patients are a heterogeneous population, encompassing those at high risk of developing shock due to isolated myocardial dysfunction to those critically ill patients with severe multi-organ dysfunction or resuscitated cardiac arrest. In this issue of the Journal, data from three nationwide French registries conducted 5 years apart and including approximately 10 000 consecutive AMI patients admitted to intensive cardiovascular care units are presented.13 The overall prevalence of CS complicating AMI halved in a decade: from 5.9% in 2005 to 2.8% in 2015. This reduction was observed both for CS developing prior to admission (primary CS), and even more for CS developing after hospitalization and coronary reperfusion (secondary CS). However, the number of CS patients presenting after out-of-hospital cardiac arrest (OHCA) increased over time.13 Despite an increase in early medications and percutaneous coronary intervention (PCI), 1-year mortality remained exceptionally high (58%) and did not change over the decade of observation. This was the result of different trends in primary vs. secondary CS: mortality decreased significantly from 60% to 38% (P = 0.038) in patients with primary CS, but remained unchanged in patients developing secondary CS (from 64.5% to 69.1%; P = 0.731).13 The decreasing incidence of CS developed during hospitalization, more evident in western countries, might be due to an earlier arrival at hospital and an increased usage of timely PCI with reduction in infarct size and subsequent incidence of mechanical complications and acute heart failure. On the other hand, with improvements in AMI network and medical care leading to more frequent and rapid transportation of even sicker patients, the increased incidence of advanced heart failure developing after AMI, early and careful attention to the maintenance of acceptable haemodynamic parameters, novel treatment options and adherence to effective secondary prevention strategies, CS on admission now represents the majority of CS cases. For the same reason, resuscitated OHCA patients are steadily increasing over time, encompassing more than 50% of cases in recent studies such as the CULPRIT-SHOCK (Culprit Lesion Only PCI versus Multivessel PCI in Cardiogenic Shock) trial.14 Notably, adjusting for OHCA, the high rate of mortality for CS is gradually decreasing over decades.15 Therefore, in order to further reduce the trend in CS complicating AMI, it seems crucial to implement emergency networks and protocols for early recognizing ‘pre-shock’ conditions, during which a potentially reversible haemodynamic state exists and for reducing delays in reperfusion, especially in patients with OHCA at increased risk for developing CS. In this regard, in the analysis published in this issue of the Journal,13 some baseline characteristics such as older age, OHCA, and ST-elevation myocardial infarction were associated with both primary and secondary CS, while higher C-reactive protein levels, left bundle branch block or right bundle branch block on admission were specifically associated with secondary CS. These findings might be used to better identify patients at high risk of developing CS during hospitalization following AMI, facilitating prompt clinical decision making. Another important aspect emerging from the analysis of the French registries is that more patients with CS were treated with mechanical ventilation and cardiac assist devices over the period of observation.13 These findings may reflect either more severe forms of CS in current patient populations, or simply a change toward a broader use of more ‘aggressive’ therapies. To date, interventions targeted to improve systemic perfusion in patients with CS have not yielded the anticipated benefits with respect to clinical outcomes. Although venoarterial extracorporeal membrane oxygenation is a potentially attractive alternative and is increasingly being used to preserve organ perfusion and prevent multisystem organ dysfunction in patients with CS, specific randomized clinical trials are warranted in order to identify the best timing for implantation and the ideal clinical profile who would benefit most. Conflict of interest: none declared.

Topics & Concepts