Cardiac-Resynchronization Therapy in Heart Failure With a Narrow QRS Complex
What is the effect of cardiac-resynchronization therapy (CRT) on morbidity and mortality among patients with symptomatic heart failure, a narrow QRS complex, and echocardiographic evidence of left ventricular dyssynchrony?
The EchoCRT (Echocardiography Guided Cardiac Resynchronization Therapy) investigators conducted a randomized trial involving 115 centers to evaluate the effect of CRT in patients with New York Heart Association class III or IV heart failure, a left ventricular ejection fraction of 35% or less, a QRS duration of <130 msec, and echocardiographic evidence of left ventricular dyssynchrony. All patients underwent device implantation and were randomly assigned to have CRT capability turned on or off. The primary efficacy outcome was the composite of death from any cause or first hospitalization for worsening heart failure. Time-to-event curves were estimated with the use of the Kaplan–Meier method.
The study was stopped for futility on the recommendation of the data and safety monitoring board. At study closure, the 809 patients who had undergone randomization had been followed for a mean of 19.4 months. The primary outcome occurred in 116 of 404 patients in the CRT group, as compared with 102 of 405 in the control group (28.7% vs. 25.2%; hazard ratio [HR], 1.20; 95% confidence interval [CI], 0.92-1.57; p = 0.15). There were 45 deaths in the CRT group and 26 in the control group (11.1% vs. 6.4%; HR, 1.81; 95% CI, 1.11-2.93; p = 0.02).
The authors concluded that in patients with systolic heart failure and a QRS duration of <130 msec, CRT does not reduce the rate of death or hospitalization for heart failure, and may increase mortality.
In this study, the use of CRT did not reduce the rate of death from any cause or first hospitalization for heart failure among patients with symptomatic heart failure, a left ventricular ejection fraction of 35% or less, and a QRS duration of <130 msec. Furthermore, the observed excess mortality with CRT in this trial is of concern. The excess mortality was due to a significant increase in the rate of death from cardiovascular causes among patients receiving CRT. For now, QRS width >150 msec (with or without mechanical dyssynchrony), as recommended in current guidelines, remains the primary determinant of response to CRT, and should guide CRT implantation among patients with symptomatic heart failure.
Keywords: Heart Failure, Cardiac Resynchronization Therapy, Echocardiography
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