Does active cardiac resynchronization therapy improve exercise duration in patients with severe left ventricular dysfunction and a QRS duration <120 milliseconds?
In patients with symptomatic heart failure, LVEF ≤35%, and a narrow QRS complex (<120 ms), cardiac resynchronization therapy does not improve clinical outcomes or left ventricular remodeling and may cause harm.
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.
Thibault et al. (2013) studied this question.
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