Background: Although the benefits of cardiac resynchronization therapy are well established in selected patients with heart failure and a prolonged QRS duration, salutary effects in patients with narrow QRS complexes remain to be demonstrated.
Methods and results: The Evaluation of Resynchronization Therapy for Heart Failure (LESSER-EARTH) trial is a randomized, double-blind, 12-center study that was designed to compare the effects of active and inactive cardiac resynchronization therapy in patients with severe left ventricular dysfunction and a QRS duration <120 milliseconds. The trial was interrupted prematurely by the Data Safety and Monitoring Board because of futility and safety concerns after 85 patients were randomized. Changes in exercise duration after 12 months were no different in patients with and without active cardiac resynchronization therapy (-0.7 minutes [95% confidence interval (CI), -2.9 to 1.5] versus 0.8 minutes [95% CI, -1.2 to 2.9]; P=0.31]. Similarly, no significant differences were observed in left ventricular end-systolic volumes (-6.4 mL [95% CI, -18.8 to 5.9] versus 3.1 mL [95% CI, -9.2 to 15.5]; P=0.28) and ejection fraction (3.3% [95% CI, 0.7-6.0] versus 2.1% [95% CI, -0.5 to 4.8]; P=0.52). Moreover, cardiac resynchronization therapy was associated with a significant reduction in the 6-minute walk distance (-11.3 m [95% CI, -31.7 to 9.7] versus 25.3 m [95% CI, 6.1-44.5]; P=0.01), an increase in QRS duration (40.2 milliseconds [95% CI, 34.2-46.2] versus 3.4 milliseconds [95% CI, 0.6-6.2]; P<0.0001), and a nonsignificant trend toward an increase in heart failure-related hospitalizations (15 hospitalizations in 5 patients versus 4 hospitalizations in 4 patients).
Conclusions: In patients with a left ventricular ejection fraction ≤35%, symptoms of heart failure, and a QRS duration <120 milliseconds, cardiac resynchronization therapy did not improve clinical outcomes or left ventricular remodeling and was associated with potential harm.
Clinical trial registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00900549.