Efficacy of a dual chamber defibrillator with atrial antitachycardia functions in treating spontaneous atrial tachyarrhythmias in patients with life-threatening ventricular tachyarrhythmias.

BACKGROUND Atrial fibrillation has a high incidence in patients wearing an implantable cardioverter defibrillator for ventricular tachyarrhythmias and may lead to palpitations, heart failure, angina, stroke and inappropriate defibrillator discharge. The aim of the study was to evaluate the efficacy of a dual chamber defibrillator with atrial antitachycardia functions in treating spontaneous atrial tachyarrhythmias. METHODS One hundred and twelve patients, 88 male, mean age 64+/-11 years, were enrolled. Seventy-six had ischaemic heart disease, 21 idiopathic dilated cardiomyopathy, nine other heart diseases, six no structural heart disease. The mean left ventricular ejection fraction was 40+/-11%. Sixty-two had prior atrial tachyarrhythmias. RESULTS Follow-up lasted 11+/-9 months (range 1-42). Among 933 ventricular tachyarrhythmia episodes, 100% of ventricular fibrillation and 92% of ventricular tachycardia were successfully cardioverted. Among 414 detected sustained atrial tachyarrhythmias, 195 were classified as atrial tachycardia (47.1%), 192 as atrial fibrillation (46.4%) and 27 (6.5%) as sinus rhythm. The detection-positive predictive value was 93.5%. Therapy success rates: antitachy pacing on atrial tachycardia = 71.3% (crude estimate); 66.1% (adjusted estimate); 50 Hertz on atrial fibrillation=36.2% (crude estimate); 13.5% (adjusted estimate); atrial shock on atrial fibrillation = 62.5% (mean energy 7.8+/-14.1J). Shock efficacy was 32% when delivered energy was < or = 2 atrial defibrillation threshold at implant and 92% when >2. Duration of successfully treated atrial episodes was significantly lower than that of unsuccessfully treated (6+/-26 min vs 42+/-60). CONCLUSIONS Atrial antitachy pacing and shock therapies demonstrated very high efficacy in treating atrial tachyarrhythmias in defibrillator patients.