Effects of antiarrhythmic drugs on inappropriate shocks in patients with implantable cardioverter defibrillators

Background: Patients with atrial fibrillation (AF) or congestive heart failure (CHF) are more vulnerable to inappropriate shocks from implantable cardioverter-defibrillators (ICDs), but the effect of antiarrhythmic drugs in these patients remains unknown. Methods and Results: A total of 55 patients with AF and/or CHF (New York Heart Association functional class ≥III) who had ICDs were divided into 3 groups [amiodarone (n=24), sotalol (n=12), β-blocker (n=19)] and the cumulative rates of inappropriate shocks were compared. The baseline characteristics of the 3 groups were not significantly different. The 4-year event rate of inappropriate shocks was 27.3% hi the amiodarone group, 54.3% in the sotalol group, and 70.6% in the β-blocker group (amiodarone vs β-blocker: log-rank p=0.003; sotalol vs β-blocker: log-rank p=0.16; amiodarone vs sotalol: log-rank p=0.29). Amiodarone reduced the risk of inappropriate shocks significantly as compared with β-blockers (hazard ratio (HR) 0.17; 95% confidence interval (CI) 0.05-0.64; p=0.008), whereas sotalol did not (HR 0.57; 95%CI 0.19-1.68; p=0.3). Amiodarone was discontinued in 4 patients (16.7%) because of pulmonary toxicity and the dose was reduced in 4 patients (16.7%) because of a thyroid function abnormality. Conclusions: Amiodarone is more effective than sotalol or β-blockers in preventing inappropriate ICD shocks in patients with AF or CHF, but it has a significant risk of drug-related adverse effects.