Effect of long-term resynchronization therapy on left ventricular remodeling in pacemaker patients upgraded to biventricular devices.

Right ventricular pacing resulted in abnormal ventricular depolarization and an activation pattern similar to left branch bundle block. In some circumstances, it may exacerbate symptoms of heart failure and increase hospital admission rates. The objective of this study was to assess the effects of long-term ventricular resynchronization therapy on echocardiographic parameters of left ventricular (LV) remodeling in patients with moderate to severe heart failure who were upgraded from single- to biventricular pacing. Twenty-six consecutive pacemaker-dependent patients (20 men; mean age 61 +/- 20 years) who underwent placement of an LV lead to upgrade their conventional pacing system to biventricular pacing were included in the study. All patients had heart failure symptoms, received the maximum tolerated medical therapy, and were stable for >or=1 month before the upgrade. Echocardiography and electrocardiography were performed before the pacemaker upgrade and at follow-up (mean duration 15 +/- 9 months). QRS duration decreased significantly from 176 +/- 23 to 154 +/- 19 ms (p <0.001). LV end-diastolic volume (p = 0.006) and LV end-systolic volume (p = 0.004) decreased at follow-up compared with baseline. The decrease in LV volumes observed during follow-up was accompanied by a significant increase in ejection fraction (39 +/- 11% to 46 +/- 10%; p = 0.001) and decrease in LV myocardial performance index (0.84 +/- 0.18 to 0.68 +/- 0.14; p = 0.001). The upgrade of conventional pacing to biventricular pacing resulted in significant prolongation of normalized LV filling time (p = 0.01) and shortening of isovolumic contraction time (p 0.002). In addition, biventricular pacing significantly (V-V interval = 0) reduced intra- (44 +/- 11 vs 18 +/- 12 ms; p <0.001) and interventricular dyssynchrony (78 +/- 33 vs 49 +/- 22 ms; p <0.001). In conclusion, these findings suggested that in patients with advanced heart failure and continuous right ventricular pacing, upgrading to biventricular system resulted in significant reverse LV remodeling in the long-term follow-up and improvement in overall synchronicity of ventricular function.