Bachmann bundle and its arterial supply: Imaging with multidetector CT - Implications for interatrial conduction abnormalities and arrhythmias

Purpose: To retrospectively investigate anatomy of Bachmann bundle (BB) and its vascular supply at 64-section multidetector computed tomography (CT) in healthy patients and patients with abnormalities. Materials and Methods: The institutional review board approved this HIPAA-compliant study and waived informed consent. Clinical histories, electrocardiograms (ECGs), and coronary 64-section multidetector CT angiograms in 317 patients were reviewed (healthy group, 164; group with abnormalities, 153). Among patients with abnormalities, 68 had atrial fibrillation (AF) or interatrial conduction block (IAB) (P wave duration, ≥120 msec), 46 had severe coronary artery disease (CAD) (≥70% stenosis of coronary artery giving rise to sinuatrial node [SAN] artery), and 39 had severe CAD and an abnormal ECG (AF or IAB). Length, anteroposterior and superoinferior diameters, attenuation, and vascular supply of BB were studied. Student t test for continuous variables and contingency tables for categorical variables were used. Results: BB was visualized, to greater degree, in the healthy group (90.2% vs 73.9% for group with abnormalities, P < .001). Visualization of BB was similar among subgroups with abnormalities: 71.7% in patients with severe CAD, 73.5% in patients with abnormal ECG, and 76.9% in patients with severe CAD and abnormal ECG. BB measurements were similar for both groups. Patients with nonvisualized BB displayed lower overall mean attenuation in the region, with -30.6 HU ± 33.4 (standard deviation), but mean attenuation in healthy patients was 51.3 HU ± 59.9 (P < .001). This finding suggests fatty infiltration. BB and BB region were mainly supplied by the right SAN artery (55.5%), followed by the left SAN artery (39.6%) and both SAN arteries (4.9%). In the group with abnormalities, there was a significant difference for SAN artery nonvisualization between those with and without identifiable BB (P = .001). Conclusion: BB and its vascular supply can easily be demarcated on cardiac CT images. BB was visualized less in patients with severe CAD and abnormal ECG, a finding that suggests that disease of BB fibers may play a role in development of atrial arrhythmias.