Effect of concomitant antiarrhythmic therapy on survival in patients with implantable cardioverter defibrillators

Background: Application of implantable cardioverter defibrillator (ICD) therapy is expanding to include both primary and secondary prevention of sudden cardiac death and has been proven to be superior to conventional antiarrhythmic therapies. Concomitant antiarrhythmic drug therapy in patients with ICD is common. These drugs are potentially proarrhythmic, alter defibrillation thresholds, and may affect response to device therapy. However, the impact of concomitant antiarrhythmic drug therapy on survival in patients with ICD devices is unknown. Methods: We investigated the effect of different antiarrhythmic drugs on survival when given concomitantly in 360 consecutive ICD patients from our university medical center. Mortality data were obtained from the national death index. Survival analysis was performed using the Kaplan-Meier method. Corrections for significant covariates and group differences were made using the Cox regression model. Results: Patients were followed up for 4.4 +/- 3.7 years. There were 68 deaths over this period with a 5-year survival of 80%. Patient characteristics were: age 62 +/- 13 years, left ventricular (LV) ejection fraction (EF) 33 +/- 17%, ischemic etiology of LV dysfunction 68%, diabetes mellitus 19%, hypertension 49%, atrial fibrillation 23%, digoxin 43%, P-blocker 46%, amiodurone 28%, and sotalol 9%. The use of beta-blockers was associated with a better survival (P = 0.0005). This effect persisted after correcting for age, heart rate, EF, and ischemic etiology. The beneficial effect of beta-blocker was unrelated to its effect on heart rate. Digoxin use was associated with a lower survival only on univariute analysis (P = 0.006), but not after adjusting for other variables on a Cox regression model (P = 0.093). Amiodarone and sotalol were found to have a neutral effect on survival. Conclusion: In patients with ICDs, beta-blockers had a favorable effect on survival. Sotalol and amiodorone had a neutral effect on survival. There was a trend toward a deleterious effect with digoxin use. These findings suggest a need for further investigation addressing survival effects of antiarrhythmic drugs when given concomitantly in patients with ICDs.