Conduction mapping during complex congenital heart surgery: Creating a predictive model of conduction anatomy

Objectives: The study objectives were to report on a growing experience of con-duction system mapping during complex congenital heart surgery and create a pre-dictive model of conduction anatomy.Methods: Patients undergoing complex cardiac repair with conduction mapping were studied. Intraoperative mapping used a multielectrode catheter to collect His bundle electrograms in the open, decompressed, beating heart. Patient anat-omy, operative details, His bundle location, and postoperative conduction status were analyzed. By using classification and regression tree analysis, a predictive model of conduction location was created.Results: A total of 109 patients underwent mapping. Median age and weight were 1.8 years (range, 0.2-14.9) and 10.8 kg (range, 3.5-50.4), respectively. Conduction was identified in 96% (105/109). Median mapping time was 6 minutes (range, 2-33). Anatomy included atrioventricular canal defect, double outlet right ventricle, com-plex transposition of the great arteries, and multiple ventricular septal defects. By classification and regression tree analysis, ventricular looping and visceroatrial situs were the greatest discriminators of conduction location. A total of 94 of 105 pa-tients (89.5%) were free of complete heart block. Only 1 patient (2.9%) with het-erotaxy syndrome developed complete heart block.Conclusions: The precise anatomic location of the conduction system in patients with complex congenital heart defects can be difficult for the surgeon to accurately predict. Intraoperative conduction mapping enables localization of the His bundle and adds to our understanding of the anatomic factors associated with conduction location. Predictive modeling of conduction anatomy may build on what is already known about the conduction system and help surgeons to better anticipate con-duction location preoperatively and intraoperatively. (J Thorac Cardiovasc Surg 2023;165:1618-28)