Inducibility of atrial fibrillation is associated with disturbed activation pattern in bachmanns bundle

Abstract

Abstract Background Electrophysiological differences in Bachmann's bundle (BB) between patients with a history of atrial fibrillation (AF) and patients without prior tachyarrhythmias have been demonstrated, including a higher proportion of conduction block (CB) and longer lines of CB. However, whether conduction abnormalities in BB influence inducibility of AF is yet unknown. Purpose To investigate which electrophysiological characteristics of BB during sinus rhythm increase susceptibility to AF in patients undergoing elective cardiac surgery, using intraoperative high density epicardial mapping data. Methods Fifty-four patients without a history of AF, admitted for correction of structural cardiac disease (coronary artery disease, heart valve regurgitation or stenosis or congenital heart disease), were examined. Epicardial mapping of Bachmann's bundle during sinus rhythm was performed using a rectangle-shaped electrode array (192 electrodes, interelectrode distance: 2mm). AF was induced using bursts of fixed rate pacing. Patients in whom sustained AF was induced (lasting throughout the mapping procedure, N=34) and patients in whom AF was non-inducible (N=20) were compared with respect to lines of conduction block (CB, defined as interelectrode conduction time >12ms), total activation time of Bachmann's bundle and patterns of activation. Results AF inducibility was not related to patient characteristics. Patients in whom AF was induced showed a higher proportion of CB (3.23 (0.0–23.9)% vs 1.82 (0.048- 4.6)%, p<0.05), longer maximum lines of CB (12 (0–78)mm vs 9 (2–24)mm, p<0.05) and a longer total activation time (55.0 (24.0–154.5)ms vs 41.8 (23.0–73.0)ms, p<0.01) compared to patients in the non-inducibility group. In addition, BB was activated by more separate waves entering the mapping area from different directions in the induced AF group; more than 1 wave entered BB in 22 (65%) of the induced AF patients versus 7 (40%) of non-inducibility patients, p<0.05. Conclusion Inducibility of AF is associated with an increased proportion of CB, longer maximum continuous lines of CB, a longer total activation time of BB and more than 1 wave entering the mapping area from different directions during sinus rhythm. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Dutch Heart Foundation