The Effect of Cardiac Resynchronization on Morbidity and Mortality in Heart Failure

Background.Cardiac resynchronization reduces symptoms and improves left ventricular function in many patients with heart failure due to left ventricular systolic dysfunction and cardiac dyssynchrony.We evaluated its effects on morbidity and mortality. Methods.Patients with New York Heart Association class III or IV heart failure due to left ventricular systolic dysfunction and cardiac dyssynchrony who were receiving standard pharmacologic therapy were randomly assigned to receive medical therapy alone or with cardiac resynchronization.The primary end point was the time to death from any cause or an unplanned hospitalization for a major cardiovascular event.The principal secondary end point was death from any cause. Results.A total of 813 patients were enrolled and followed for a mean of 29.4 months.The primary end point was reached by 159 patients in the cardiac resynchronization group, as compared with 224 patients in the medical therapy group (39% vs. 55%; hazard ratio, 0.63; 95% confidence interval [CI], 0.51-0.77;p<0.001).There were 82 deaths in the cardiac resynchronization group, as compared with 120 in the medical therapy group (20% vs. 30%; hazard ratio 0.64; 95% CI, 0.48-0.85;p<0.002).As compared with medical therapy, cardiac resynchronization reduced the interventricular mechanical delay, the