Atrial overdrive pacing to prevent atrial fibrillation: insights from ASSERT.

BACKGROUND: Pacing algorithms to prevent atrial fibrillation (AF) have been tested in studies of modest size and duration with inconclusive results. OBJECTIVES: To prospectively evaluate the relationship between subclinical AF and stroke in patients 65 years of age or older with no previous AF receiving a first pacemaker or an implantable cardioverter-defibrillator for standard indications. Three months following device implantation, pacemaker patients were randomized to have continuous atrial overdrive pacing (CAOP) algorithm turned "ON" or "OFF." The primary study outcome was development of electrocardiogram-documented AF >6 minutes. RESULTS: A total of 2343 patients were randomized and followed for a mean of 2.5 years. The primary outcome occurred in 60 patients in the CAOP ON group (1.96% per year) and in 45 in the CAOP OFF group (1.44% per year; relative risk 1.38; 95% confidence interval 0.94-2.03; P = .10). Major clinical events (stroke, myocardial infarct, cardiovascular death, systemic embolism, heart failure hospitalization) occurred at similar frequencies in the 2 groups. In the CAOP ON group, 133 of the 1164 patients (11.4%) crossed over to CAOP OFF compared with 12 of the 1179 (1.0%) who crossed over from OFF to ON (P <.0001). False-positive device detections of AF were more common among patients assigned to CAOP ON (23%) than among patients assigned to CAOP OFF (7.7%; relative risk 2.99; 95% confidence interval 2.40-3.74; P <.001). Pacemaker generator replacement for battery depletion occurred in 4.4% of the subjects randomized to CAOP ON and in 2.5% of the patients assigned to CAOP OFF (relative risk 1.70; 95% confidence interval 1.08-2.67; P = .02). CONCLUSIONS: CAOP does not prevent new-onset AF, is poorly tolerated, and accelerates pulse generator battery depletion.