Abstract

Objective: To determine by means of a monitoring study the onset mechanisms of atrial fibrillation (AF) after coronary artery bypass graft surgery (CABG).

Patients and design: During elective CABG, 81 patients had one bipolar atrial and one ventricular epicardial electrode attached. These were connected to a Vitatron 900E external pacing device, which monitored the patients for four consecutive days. 12 lead ECGs were obtained if AF was clinically detected and Holter ECGs were obtained in 8 (33%) of these patients.

Results: 24 patients (30%) developed paroxysmal AF (50%), atrial flutter (17%), or both (33%). The number of AF episodes varied from 1–169 a day (median 5) and were usually of short duration (median 2.25 minutes). Pacemaker diagnostics showed much intrapatient and interpatient variability in onset mechanisms but the majority of AF onsets (71%) were preceded by either short runs of AF or multiple atrial extrasystoles. The final trigger was a conducted atrial extrasystole in 72% of cases. There were no bradycardic triggers. The Holter ECGs confirmed the device’s data.

Conclusions: The onset mechanisms of post-CABG AF are dominated by atrial extrasystoles with multiple atrial extrasystoles and short runs of AF preceding the main AF onset in the majority of cases. These results have major implications for the development of new preventive pacing algorithms.