Background: Cardiac resynchronization therapy (CRT) reduces mortality in selected patients with heart failure. However, this result may not be entirely related to the beneficial hemodynamic effects of CRT.
Objectives: The purpose of this study was to assess retrospectively the effect of CRT on the incidence of appropriate therapy in patients with an implantable cardioverter-defibrillator (ICD).
Methods: Sixty-five patients (48 men and 17 women; mean age 58 +/- 13 years) with an ICD (31 biventricular, 34 dual-chamber) were included in the study. Clinical, ECG, and ICD stored data and electrograms were collected.
Results: Biventricular and dual-chamber ICDs were implanted in 31 and 34 patients, respectively, who had either ischemic (n = 36) or dilated cardiomyopathy (n = 29). Thirty-two (49%) patients received > or =1 appropriate ICD therapy during follow-up of 11 +/- 8 months. Thirty-five percent and 62% of patients with biventricular (n = 11) and dual-chamber ICDs (n = 21), respectively, received appropriate ICD therapy during the follow-up period (odds ratio = 0.340, P = .048). Stratifying the patients according to underlying heart disease and ejection fraction resulted in an adjusted odds ratio = 0.239 (P = .029). Comparing the rate of > or =1 appropriate ICD therapy between the two groups by Kaplan-Meier analysis and the log rank test resulted in P = .027.
Conclusion: In this retrospective analysis, biventricular pacing was associated with a decreased incidence of sustained ventricular arrhythmias requiring ICD therapy. The antiarrhythmic effect of biventricular pacing could contribute to the reduction in mortality reported in recent large-scale clinical trials on CRT. However, further prospective studies are warranted to clarify this issue.