CardioExchange Archive

A large observational study published in JAMA suggests that patients with left bundle-branch block (LBBB) and longer QRS duration derive the most benefit from a cardiac resynchronization therapy defibrillator (CRT-D). The findings appear to support current, but often criticized, guidelines from the American College of Cardiology, American Heart Association, and the Heart Rhythm Society, in which a class I recommendation is restricted to patients with LBBB and QRS duration of 150 ms or greater.

Pamela Peterson and colleagues analyzed data from more than 24,000 CRT-D patients who were enrolled in the National Cardiovascular Data Registry’s ICD Registry. For the entire group, all-cause mortality was 9.2% at 1 year and 25.9% at 3 years. Hospital readmission occurred in 10.2% at 30 days and 43.3% at 1 year. Mortality and readmission rates, both before and after adjusting for other risk factors, were significantly higher in the group without LBBB and with QRS duration <150 ms.

In their report, the authors noted that their study did not contain a control group that did not receive CRT therapy and “should not lead to conclusions regarding the benefit of CRT, or the lack thereof, in patients with QRS duration of 120 to 149 ms and without LBBB.” But, they wrote, “the findings that patients with LBBB and QRS duration of 150 ms or greater had the best outcomes after accounting for differences in other measured patient characteristics are concordant with current guideline recommendation classifications.” They concluded that their findings “support the use of QRS morphology and duration to help identify patients who will have the greatest benefit from CRT-D implantation.”