Novel insights in pathophysiology of post-operative atrial fibrillation

ABSTRACT Objectives Atrial extrasystoles are usually benign, however they can also trigger atrial fibrillation. It is most likely that if atrial extrasystoles provoke a larger amount of conduction disorders and a higher degree of endo-epicardial asynchrony, the risk of post-operative atrial fibrillation increases. To test this hypothesis, we investigated the effect of programmed atrial extrasystoles on endo-epicardial conduction and post-operative atrial fibrillation. Methods Twelve patients (58% male, age 68±7 years) underwent simultaneous endo-epicardial mapping (256 electrodes) of the right atrium during sinus rhythm and programmed atrial extrasystoles provoked from the right atrial free wall. Areas of conduction block were defined as conduction delays of ≥12ms and endo-epicardial asynchrony as activation time differences of exact opposite electrodes of ≥15ms. Results Endo-epicardial mapping data of all programmed atrial extrasystoles were analyzed and compared with sinus rhythm (median preceding cycle length=531ms [345-787] and median sinus rhythm CL=843ms [701-992]). All programmed atrial extrasystoles were aberrant (severe, moderate and mildly aberrant, respectively n=6, 3 and 3) and had a mean prematurity index of 50.1±11.9%. The amount of endo-epicardial asynchrony (1% [1-2] vs 6.7 [2.7-16.9], p=0.006) and conduction block (1.4% [0.6-2.6] vs 8.5% [4.2-10.4], p=0.005) both increased during programmed atrial extrasystoles. Interestingly, conduction block during programmed atrial extrasystoles was more severe in patients (n=4, 33.3%) who developed post-operative atrial fibrillation (5.1% [2.9-8.8] vs 11.3% [10.1-12.1], p=0.004). Conclusion Atrial conduction disorders and endo-epicardial asynchrony, which play an important role in arrhythmogenesis, are enhanced during programmed atrial extrasystoles compared to sinus rhythm. The findings of this pilot study provide a possible explanation for enhanced vulnerability for post-operative atrial extrasystoles to induce post-operative atrial fibrillation in patients after cardiac surgery.