Cardiogenic Shock: A Summary of the Randomized SHOCK Trial

Venu Menon, MD, Rupert Fincke, MD

Disclosures

CHF. 2003;9(1) 

In This Article

Abstract and Introduction

Cardiogenic shock is the most common cause of death for patients hospitalized with acute myocardial infarction. The Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock (SHOCK) trial randomly assigned 302 patients with predominant left ventricular failure following an acute myocardial infarction to a strategy of emergency revascularization or initial medical stabilization. Emergency revascularization by either coronary artery bypass grafting or angioplasty was required within 6 hours of randomization. Patients assigned to initial medical stabilization could undergo delayed revascularization at a minimum of 54 hours post-randomization. The primary end point of the study was 30-day all-cause mortality. Overall survival at 30 days did not differ significantly between the emergency revascularization and initial medical stabilization groups (53% vs. 44%; p=0.109). However, at the 6- and 12-month follow-up, there was a significant survival benefit with early revascularization (50% vs. 37%; p=0.027 and 47% vs. 34%; p=0.025, respectively). The benefit appeared to be greatest for those less than 75 years of age, with 20 lives saved at 6 months per 100 patients treated. According to the results of the SHOCK trial, the American College of Cardiology/American Heart Association guidelines for myocardial infarction now recommend emergency revascularization for patients younger than 75 years with cardiogenic shock.

Cardiogenic shock (CS) is the most common cause of death for patients hospitalized with acute myocardial infarction (MI).[1,2] Although the overall incidence remains unchanged, mortality rates from this clinical entity appear to be declining.[3,4] This favorable trend has been associated with increasing utilization of reperfusion therapy, revascularization, and hemodynamic support with intra-aortic balloon pumping (IABP). The superior outcome among CS patients in the United States over their non-American counterparts has also been attributed to this aggressive approach.[5] Despite this positive relationship, these observations do not directly prove cause and effect. Revascularization in these reports was not protocol-mandated, but driven by individual clinical judgment. Sophisticated post-hoc statistical adjustment cannot adjust for unmeasured variables and this sets up the possibility of selection bias.[6]

Designing a randomized, controlled trial in the setting of CS complicating acute MI is limited by the need for expedient therapy, the rapid demise of critically ill patients, and physician bias. Prospective data in this area were, however, clearly warranted. The National Heart, Lung, and Blood Institute supported the SHOCK (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock) trial[7] and (S)MASH (Swiss) Multicenter Trial of Angioplasty for Shock,[8] which were designed to fill this void. Both trials examined the benefit of early revascularization in the setting of CS. Regrettably, (S)MASH was terminated prematurely due to insufficient patient enrollment. The SHOCK trial was successfully completed and enrollment was stopped in November, 1998. In this review, we briefly describe the SHOCK trial design and highlight salient trial findings.

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