Racial differences in outcome in the Multicenter UnSustained Tachycardia Trial (MUSTT): a comparison of whites versus blacks

Abstract

Background: The Multicenter UnSustained Tachycardia Trial (MUSTT) demonstrated the benefit of implantable cardioverter-defibrillators (ICDs) in patients with coronary disease, asymptomatic nonsustained ventricular tachycardia, and reduced left ventricular function. Previous studies have shown racial differences in risk of sudden death in patients with ischemic heart disease.

Methods and results: We analyzed the influence of race on results of MUSTT. Whites were more likely to have prior revascularization and inducible, randomizable sustained ventricular arrhythmias and less likely to have left ventricular hypertrophy than were blacks. Compared with blacks, whites randomly assigned to electrophysiologically (EP)-guided therapy had a lower risk of arrhythmic death/cardiac arrest (adjusted P=0.003) and lower total mortality rates (adjusted P=0.051). In contrast, there was no racial difference in the risk of arrhythmic death/cardiac arrest among patients randomly assigned to no EP-guided therapy (adjusted P=0.477). Among whites, EP-guided therapy resulted in a survival benefit compared with no EP-guided therapy. However, survival of blacks randomly assigned to no EP-guided therapy was better than blacks receiving EP-guided therapy. This difference is partially explained by a higher ICD implantation rate in whites versus blacks (50% versus 28%, P=0.034). Whites were more likely to remain inducible after serial EP-guided drug testing (67% versus 42%, P=0.011), making them more likely to become eligible for ICDs.

Conclusions: The outcome in this trial and the benefit of EP-guided therapy appeared to be influenced by race. In addition to differences in ICD implantation rates, differences in arrhythmic substrates and proarrhythmic responses to antiarrhythmic drugs may have influenced outcome.