Ventricular septation for double inlet ventricle: Avoiding conduction injury

Objectives: Although conduction location can be reliably predicted in double inlet ventricle, ventricular septation continues to carry a significant risk of complete heart block. This study describes our experience using intraoperative conduction mapping during ventricular septation. Methods: Patients undergoing ventricular septation from 2017 to 2023 were identified. Conduction mapping was performed on the open, decompressed, beating heart to identify the His bundle. Mapped His bundle locations were compared with those predicted from magnetic resonance imaging diagnoses by a senior pediatric cardiac electrophysiologist blinded to mapping results. Results: Ventricular septation was performed in 31 patients, 25 with hypoplastic right ventricles and 6 with hypoplastic left ventricles. Two-stage septation was performed in 25 patients, and single-stage septation was performed in 6 patients. Mapped conduction location was performed in the last 25 consecutive patients. Mapped conduction location was concordant with expected location in 21 of 22 patients with predictions. Complete heart block requiring a permanent pacemaker occurred in 4 patients despite successful mapping, whereas 10 patients required other reoperations, most commonly to address residual atrioventricular valve regurgitation or subpulmonary obstruction from the ventricular septal defect patch. There has been no perioperative mortality, need for single-ventricle palliation, or heart transplantation. All 13 patients who have progressed to complete septation and 18 patients with interstage circulation have acceptable hemodynamics, preserved ventricular function, and no heart failure symptoms at latest follow-up. Conclusions: Ventricular septation represents an alternative to the Fontan that can be performed safely in a subset of patients with acceptable early outcomes. Conduction mapping is an adjunct strategy that may add precision to well- established rules for reliably predicting conduction location.