Antiarrhythmic Effect of Reverse Ventricular Remodeling Induced by Cardiac Resynchronization Therapy. The InSync ICD (Implantable Cardioverter-Defibrillator) Italian Registry

Objectives: We investigated whether the reverse remodeling after cardiac resynchronization therapy (CRT) might reduce the occurrence of ventricular arrhythmias (VAs). Background: It is currently debated whether CRT has an effect on the burden of VAs. Methods: The study included 398 patients treated with a CRT defibrillator and with a follow-up of at least 12 months. Spontaneous VAs detected by the device were reviewed and validated. Results: A significant reduction in VA episodes and shock therapies was evident during the follow-up with greater decrease after 1 month. After 6 months of CRT, 227 patients (57%) showed a reduction in end-systolic volume of ≥10% and were defined as "responders." The baseline characteristics were similar between the responders and the nonresponders. Nonetheless, the proportion of patients with recurrence of VA after 1 month of CRT was significantly lower in responders (32% vs. 43%, p = 0.024). Among baseline variables no parameters emerged as predictors of tachyarrhythmia recurrence. However, receiver-operating curve analysis recognized a reduction of left ventricular end-systolic volume at 6 months of 13% as the best cutoff to identify the reduction of VAs (with a sensitivity of 58% and a specificity of 54%). Conclusions: In patients treated with CRT defibrillators, a reduction in ventricular arrhythmic events occurs during the initial 12 months after implant and is correlated with the degree of ventricular remodeling induced by the therapy. Patients demonstrating reverse remodeling at midterm follow-up show a reduction in arrhythmias soon after the implant, pronounced improvements at long-term, and a better survival.