Treatment of atrial fibrillation with an implantable atrial defibrillator — long term results

OBJECTIVES: To evaluate the long-term outcome with an implantable atrial defibrillator (IAD) in patients with recurrent atrial fibrillation (AF). BACKGROUND: Maintenance of sinus rhythm using repeated internal cardioversion shocks has been shown to be effective and safe in short-term studies but long term follow-up is unknown. METHODS: Since 1995, 136 patients (30 women) with symptomatic, drug-refractory atrial fibrillation were implanted with an IAD (METRIX, InControl). This analysis was performed after a median of 40 (range 7-66) months after implantation. RESULTS: In 26 patients, the programmed mode was not documented during last follow-up, four patients had died. Of the remaining 106 patients (mean age 58+/-10, range 34 - 79 years), 39 were actively delivering therapy with the device, in 14 patients the device was used to monitor the arrhythmia but no shocks were delivered, and in 53 patients it was turned off or explanted. Increases in defibrillation thresholds (n=7), patient intolerance of multiple cardioversion shocks (n=15), and significant bradycardia requiring dual-chamber pacing (n=12) were the main reasons for discontinuation of therapy in addition to battery depletion (n=19). After explantation, efforts to maintain sinus rhythm were continued in 17 patients whereas rate control was attempted in 36 patients. CONCLUSIONS: A strategy of maintaining sinus rhythm long-term with an IAD is feasible in a proportion of patients. However, patient selection is critical, and technical improvements (i.e. higher shock energies, dual-chamber pacing and additional preventive and anti-tachycardia pacing algorithms) are required to increase the number of patients having long term benefit, and frequent arrhythmia recurrences and patient intolerance to repeated cardioversion shocks remain a major limitation.