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Cheuk-Kit Wong and Harvey D White
American Heart Journal Volume 7 No.1

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Cardiogenic shock from left ventricular dysfunction complicating an acute ST-elevation myocardial infarction is associated with high mortality. Much of the current understanding of the importance of emergency revascularization comes from the SHOCK trial. Mortality benefits combined with improved quality of life among the survivors justify the routine use of emergency revascularization in patients < 75 years of age and in selected patients >75 years of age.This article discusses the SHOCK trial and potential mechanisms of benefit from revascularization as well as more recent information. Adjunctive therapies have been disappointing. To further improve outcomes, earlier pre-emptive and preventive strategies to ensure early revascularization should be pursued.

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The incidence of cardiogenic shock has not changed in the reperfusion era. The National Registry of Myocardial Infarction (NRMI) from January 1995 to May 2004 at 775 US hospitals with revascularization capability included 293,633 patients with ST-elevation myocardial infarction (MI), 25,311 (8.6%) of whom had cardiogenic shock. Presentation with cardiogenic shock occurred in 7,356 patients (2.9%).¹ The mortality rate in this study fell from 60.3 to 47.9% over 10 years. In-hospital mortality from ardiogenic shock from hospitals in a single community-Worcester, MA-also fell by 10% for the period 1975-1990 from approximately 80% to approximately 60% during 1995-1997.² In the GUSTO I trial, 1,891 patients with cardiogenic shock were enrolled in the US; 30-day mortality was 49.6% and mortality at 11 years was 72.2%.³ Annual mortality rates of 2.4% per year for 30-day survivors following shock were similar to those without shock.

Much of our understanding of the benefit of emergency revascularization in managing cardiogenic shock comes from the SHOCK (SHould we emergently revascularize Occluded Coronaries in cardiogenic shocK?) trial,⁴ a landmark study that also raised intriguing questions. The SHOCK trial was a randomized, controlled study designed to examine whether emergency revascularization (ERV)- either angioplasty or bypass surgery-was superior to a strategy of initial stabilization by means of intensive medical therapy (IMS). IMS included a recommendation for intra-aortic balloon counterpulsation, fibrinolytic therapy if feasible, and delayed revascularization ifclinically warranted. The initial assumption in the trial, designed in 1992, was that emergency revascularization would result in a 20% absolute reduction in the primary end-point of overall mortality at 30 days.^4,5 At the end of 5.5 years, the trial had randomized 152 patients to ERV, with percutaneous coronary intervention (PCI) for onevessel disease and emergency coronary artery bypass grafting (CABG) or staged percutaneous coronary intervention (PCI) for multivessel disease, and 150 to the IMS strategy. The primary end-point of overall mortality at 30 days was negative-46.7% ERV versus 56.0% IMS (p=0.11)-but at six months (a secondary end-point of the trial) mortality was 50.3% for ERV versus 63.1% for IMS (p=0.027).⁴ The survival advantage of an absolute 13 percentage points persisted at one year (46.7 versus 33.6%; p< 0.03) and through six years (32.8 versus 19.6%; p< 0.03).^6,7 Figure 1 shows one-year survival by treatment assignment in the SHOCK trial when left ventricular ejection fraction was used as an independent baseline variable. Of note, most survivors improved after discharge and were in New York Heart Association (NYHA) class I or II at six and 12 months after discharge (see Figure 2).⁸

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