New insights into the initiation of atrial fibrillation - A detailed intraindividual and interindividual analysis of the spontaneous onset of atrial fibrillation using new diagnostic pacemaker features

Background: This study investigated onset scenarios of atrial fibrillation (AF), the first phase of the Atrial Fibrillation Therapy ( AFT) trial, to determine potential arrhythmogenic triggers as targets for atrial pacing algorithms that have been proposed for prevention of AF. Methods and Results: Ninety-eight patients (58 men; age 65 +/- 11 years) with recurrent, symptomatic, drug-refractory AF and a conventional pacemaker indication in 31 of 98 received a dual-chamber pacemaker. Using novel diagnostic pacemaker features AF onset scenarios were prospectively evaluated in 612 AF episodes during a 2-month monitoring period, with atrial pacing limited to 40 bpm. The most common onset scenario was premature atrial complexes (PACs) before AF (48% onsets per patient), followed by bradycardia (33%), sudden onset (17%), and tachycardia (0%). Combinations of onset scenarios were frequent ( median 2 different scenarios per patient). A main study finding was the significance of repetitive AF, with 33% of onsets per patient being initiated within 5 minutes of a previous AF episode. Sudden onsets were more frequent among patients with than without repetitive AF (24% versus 0% onsets per patient, P = 0.011), whereas the proportion of PACs before AF was not statistically different (50% versus 37%, P = 0.52); however, patients with repetitive AF had more PACs per hour (72 versus 29, P = 0.023) and a higher number of AF episodes per day (17 versus 0, P = 0.001) and were more likely to have at least 1 PAC-related onset (90% versus 53%, P < 0.0001). Conclusions: Novel diagnostic pacemaker features allowed a detailed individual analysis of rate and rhythm changes before AF and thus uncovered a substantial intraindividual and interindividual variability of AF onset scenarios.