The effects of chronic carvedilol therapy on QT dispersion in patients with congestive heart failure.

BACKGROUND: Carvedilol therapy reduces mortality from sudden cardiac death and progressive pump failure in congestive heart failure (CHF). However, the effect(s) of carvedilol on ventricular repolarization characteristics is unclear. AIM: The aim of the study was to investigate the effects of chronic carvedilol therapy on ventricular repolarization characteristics as assessed by QT dispersion (QTd) in patients with CHF. METHOD: Nineteen patients (age 53+/-12 years; 16 male, three female) with CHF (eight ischemic, 11 non-ischemic dilated cardiomyopathy) were prospectively included in the study. Carvedilol was administered in addition to standard therapy for CHF at a dose of 3.125 mg bid and uptitrated biweekly to the maximum tolerated dose. From standard 12-lead electrocardiograms the maximum and minimum QT intervals (QTmax, QTmin), QTd, corrected QT intervals (QTcmax, QTcmin) and corrected QTd (QTcd) values were calculated at baseline, after the 2nd and the 16th month of carvedilol therapy. RESULTS: A significant reduction was noted in the QTd and QTcd values with carvedilol therapy after the 16th month (QTd: 81+/-22 ms vs. 40+/-4.3 ms P<0.001; QTcd: 91+/-25 ms vs. 51+/-7 ms P<0.001), but not after the 2nd month (P>0.05). The resting heart rate was also significantly reduced after a 16-month course of carvedilol therapy (78+/-13 bpm vs. 66+/-15 bpm, P<0.05). Carvedilol therapy did not alter QTmax and QTcmax intervals (P>0.05), however, QT min and QTcmin significantly increased with carvedilol at the 16th month (P<0.001 and P<0.01, respectively). CONCLUSION: Long-term carvedilol therapy was associated with a reduction in QTd, an effect that might contribute to the favorable effects of carvedilol in reducing sudden cardiac death in CHF.