Epicardial connection between the right-sided pulmonary venous carina and the right atrium in patients with atrial fibrillation: A possible mechanism for preclusion of pulmonary vein isolation without carina ablation.

BACKGROUND: Ablation of the pulmonary venous carina is occasionally required for pulmonary vein isolation (PVI) despite its nonessential role in ipsilateral PVI from the anatomical (endocardial) viewpoint. Although the Bachmann bundle (BB) is a common and main interatrial band, local variations in small tongues of muscular fibers were frequently found in autopsy studies.
OBJECTIVE: We sought to clarify the effect of the electrical conduction pattern from the right atrium (RA) to the left atrium (LA) during sinus rhythm on the necessity of performing right-sided pulmonary venous carina ablation to achieve PVI.
METHODS: Study subjects comprised 37 consecutive patients undergoing initial catheter ablation of lone atrial fibrillation. During sinus rhythm, RA and LA activation maps were acquired using an electroanatomical mapping system. LA breakthroughs were classified into 3 sites: BB, fossa ovalis (FO), and right-sided pulmonary venous carina. Patients were divided into the carina-ABL (ablation) or non-carina-ABL group on the basis of the necessity of pulmonary venous carina ablation to achieve PVI.
RESULTS: Patients were classified in the non-carina-ABL group (n = 26 [70%]) and carina-ABL group (n = 8 [22%]) after excluding 3 patients (8%) because of their complex ablation lesion sets. Breakthrough occurred in the BB (n = 21 patients [62%]), FO (n = 7 [21%]), carina (n = 1 [3%]), carina and BB (n = 3 [9%]), and carina and FO (n = 2 [6%]). Carina breakthrough occurred in 6 patients (75%) in the carina-ABL group but in no patients in the non-carina-ABL group (P < .0001).
CONCLUSION: PVI was not achievable without carina ablation in one-fifth of patients, probably because of epicardial connections present between the right-sided pulmonary venous carina and the RA.