The Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy ( MADIT-CRT ) showed that early intervention with cardiac resynchronization therapy with a defibrillator ( CRT-D ) in patients with an electrocardiographic pattern showing left bundle-branch block was associated with a significant reduction in heart-failure events over a median follow-up of 2.4 years, as compared with defibrillator therapy alone.
Researchers have evaluated the effect of CRT-D on long-term survival in the MADIT-CRT population. Post-trial follow-up over a median period of 5.6 years was assessed among all 1691 surviving patients ( phase 1 ) and subsequently among 854 patients who were enrolled in post-trial registries ( phase 2 ). All reported analyses were performed on an intention-to-treat basis.
At 7 years of follow-up after initial enrollment, the cumulative rate of death from any cause among patients with left bundle-branch block was 18% among patients randomly assigned to CRT-D, as compared with 29% among those randomly assigned to defibrillator therapy alone ( adjusted hazard ratio in the CRT-D group, 0.59; P less than 0.001 ).
The long-term survival benefit of CRT-D in patients with left bundle-branch block did not differ significantly according to sex, cause of cardiomyopathy, or QRS duration.
In contrast, cardiac resynchronization therapy with a defibrillator was not associated with any clinical benefit and possibly with harm in patients without left bundle-branch block ( adjusted hazard ratio for death from any cause, 1.57; P=0.04; P less than 0.001 for interaction of treatment with QRS morphologic findings ).
In conclusion, the findings have indicated that in patients with mild heart-failure symptoms, left ventricular dysfunction, and left bundle-branch block, early intervention with CRT-D was associated with a significant long-term survival benefit. ( Xagena )
Goldenberg I et al, N Engl J Med 2014; 370:1694-1701