Prognostic significance of atrial arrhythmias in a primary prevention ICD population.

INTRODUCTION: We investigated whether primary prevention implantable cardioverter defibrillator (ICD) patients with atrial arrhythmias are at higher risk for ICD shocks and mortality compared to patients without atrial arrhythmias in a subanalysis of the PREPARE study. METHODS AND RESULTS: Details of the PREPARE study design and results have been previously reported. We now included 537 of the 700 patients enrolled in PREPARE. These patients had a dual or biventricular device and at least one device follow-up after implantation. Continuously collected device diagnostics data were used to classify patients into two groups during follow-up: with (n = 133) or without (n = 404) atrial tachycardia/atrial fibrillation (AT/AF). The primary outcomes were ICD shocks and mortality. Subjects were followed for a mean of 333 ± 73 (range 5-365) days. During a follow-up of 1 year, ICD shocks occurred in 44 (8%) patients. Significantly, more patients with AT/AF received a shock (13.0% vs 6.9%, P = 0.03), with inappropriate shocks accounting for the majority of the difference (6.9% vs 2.6%, P = 0.02). There was no difference in prevalence of shocks between patients with and without a history of AF. Mortality was similar in patients with and without AT/AF, whether detected during the study or prior to the study. In addition, the 34 subjects with high average ventricular rate (≥110 beats per minute) during AT/AF had a higher risk of an inappropriate shock (21.0% vs 2.1%, P < 0.01). CONCLUSION: Primary prevention ICD patients with AT/AF are more likely to receive shocks, especially inappropriate shocks. Mortality was not higher in AT/AF patients. (PACE 2011; 34:1070-1079).