Beta-Blocker Therapy Induces Ventricular Resynchronization in Dilated Cardiomyopathy With Narrow QRS Complex

ObjectivesWe sought to evaluate the effects of beta-blocker therapy on regional and global myocardial mechanics in addition to ventricular synchrony in patients with heart failure and normal QRS by using tissue Doppler and strain echocardiography.BackgroundIt is unknown whether beta-blocker therapy can influence mechanical synchrony.MethodsConventional and strain echocardiography were performed in 15 healthy age-matched volunteers and in 25 patients with idiopathic dilated cardiomyopathy (IDC). Of these, 15 IDC patients on standard heart failure therapy were studied prior to and at 1 and 6 months after initiation of carvedilol therapy and compared to the controls.ResultsThere was significant mechanical dyssynchrony in IDC compared with control patients. Patients placed on carvedilol demonstrated a significant decrease in the inferoseptal to lateral wall delay in peak strain (normalized to the R-R interval) between baseline and 1 month and between baseline and 6 months. Similarly, global time to peak segmental strain (455 ± 51 ms vs. 423 ± 59 ms, respectively, p = 0.02, and 455 ± 51 ms vs. 415 ± 50 ms, respectively, p = 0.01) and the coefficient of variation of the time to peak segmental strain decreased (17 ± 4% vs. 15 ± 5%, respectively, p = 0.02, and 17 ± 4% vs. 14 ± 5%, respectively, p = 0.03), from baseline to 1 month and between baseline and 6 months, respectively. Global strain significantly increased from baseline to 1 month (−8.2 ± 1.8 to −10.4 ± 3.9, respectively, p = 0.01) and between baseline and 6 months (−8.2 ± 1.8% to −12.0 ± 3.2%, respectively, p = 0.008). Improvements in left ventricular ejection fraction and reverse remodeling were coincident with reductions in mechanical dyssynchrony.ConclusionsThe use of carvedilol improves contractile function and dyssynchrony in heart failure patients with normal QRS.