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.