Cardiogenic shock (CS) develops in about 6% of patients who suffer an acute myocardial infarction (AMI), with a relative incidence of 1 in 40 AMI patients [American Heart Association. Heart Disease and Stroke Statistics–2011 Update. 2011]. The rate of mortality associated with CS after AMI continues to remain at about 45% to 50%, unchanged from 1997 to 2006, despite the increased use of an intra-aortic balloon pump (IABP) and percutaneous coronary intervention (PCI) and the decreased use of thrombolysis and coronary bypass surgery [Jeger RV et al. Ann Intern Med. 2008].

The time to intervene is within 90 minutes to reverse CS or the opportunity to repair the heart is lost, based on physiological responses to CS, stated Ramesh Daggubati, MD, East Carolina Heart Institute at Vidant Medical Center, East Carolina University, Greenville, North Carolina, USA. A device for hemodynamic (HD) support should be considered when a moderate dose of inotropes is needed, said Dr Daggubati. None of the most commonly used devices (eg, IABP, TandemHeart, and Impella), however, have been shown to reduce mortality, despite their ability to improve hemodynamics. The limited beneficial effects and the increased side effects associated with the current drugs and devices to treat CS are summarized in Table 1.

The lack of a mortality benefit with IABP was shown in the IABP SHOCK II study [Thiele H et al. Lancet. 2013] and in a meta-analysis of studies conducted in the 1990s comparing it to no IABP [Sjauw KD et al. Eur Heart J. 2009], which also showed that mortality was about 6% higher with IABP in patients who underwent PCI, based on pooled data from the National Registry of Myocardial Infarction 2 and the Amsterdam Medical Center Cardiogenic Shock registries. IABP increased the risk of stroke by 2% (95% CI, 0 to 4; P = .03) and bleeding by 6% (95% CI, 1 to 11; P = .02), according to this meta-analysis.

HD support with IABP remains controversial and is being challenged because of the lack of evidence of benefit, stated Dr Daggubati, and the new percutaneous left-ventricular assist devices (TandemHeart, Impella) provide better HD support than IABP but do not improve mortality. In the ISAR-SHOCK study, the Impella LP 2.5 device versus IABP significantly improved the primary end point of cardiac index (0.49 vs 0.11 L/min/m², respectively; P = .01), but mortality was similar (log-rank P = .97) [Seyfarth M et al. J Am Coll Cardiol. 2008].

The timing of mechanical support, however, may lead to improved outcomes. The preintervention placement of an IABP compared with no IABP or an IABP placed after the intervention in the CS group significantly reduced the incidence of ventricular fibrillation (P = .02), cardiopulmonary arrest (P = .01), and total events in the catheterization laboratory (P = .0009) [Brodie BR et al. Am J Cardiol. 1999]. A similar result was found in the Impella registry, stated Dr Daggubati, and the pre-intervention approach is being studied in the upcoming TandemHeart to Reduce Infarct Size Trial [TRIS Trial; NCT02164058]. Implementation of a CS protocol with quick escalation of percutaneous ventricular assist devices has been shown to reduce mortality of in-hospital CS in a small registry of 32 patients from 44% to 24%. Dr Daggubati presented these data at the Society of Cardiovascular and Angiography Interventions national meeting in May 2014.

The management of CS with circulatory support will evolve with new paradigm shifts and treatment protocols as technology evolves, but better identification of the patients most likely to benefit based on stronger clinical evidence is needed.