Examination of pathologic features of the right atrioventricular groove in hearts with Ebstein anomaly and correlation with arrhythmias

Background Catheter ablation of accessory pathways (APs) in patients with Ebstein anomaly (EA) has a higher recurrence rate than in subjects with normal hearts. Anatomic features could account for suboptimal ablation outcomes. Objective The purpose of this study was to examine the right atrioventricular (AV) groove in autopsy hearts with EA, correlate with clinical data, and identify features relevant for catheter ablation. Methods Thirty-three specimens with EA from our Cardiac Registry were examined. The right AV groove was inspected for gross anatomic features. Limited microscopy was performed on selected specimens. Premortem clinical data were correlated with anatomic findings. Results A prominent ridge along the right AV groove was seen in 15 of 33 specimens (45%). Ten specimens had a clinical history of AP (AP+). The extent of ventricular atrialization did not differ between AP+ and AP– groups (64 ± 63 mm/m2 vs 76 ± 42 mm/m2; P = .61), nor did the presence of visible macroscopic AV tissue connections (45% vs 51%; P = .68). The single item that differed was the presence of an AV groove ridge itself, which was significantly more common in the AP+ group (70% vs 21%; P = .03). Microscopy of ridge tissue revealed a muscular bundle in 1 AP+ specimen penetrating deep into the fibrous AV annulus that was suggestive of an AP, although complete muscular continuity was not verified in the limited sections available for examination. Conclusion A prominent ridge along the inferior right AV groove is a common feature in EA and correlates with clinical history of AP. It presents a potential obstacle to catheter ablation and may contribute to recurrence rate.