Objectives: Heterotaxy is characterized by complex venous connections and cardiac position requiring individualized strategies for Fontan. This study aimed to assess 25-year outcomes of heterotaxy patients undergone Fontan operation, with particular focus on morphological features and surgical techniques. Methods: 82 consecutive heterotaxy patients who underwent Fontan operation from 1985 to 2021 were compared to 150 with tricuspid atresia (TA) and 144 with hypoplastic left heart syndrome (HLHS). Kaplan-Meier method and Cox proportional hazard model were used for transplant-free survival and predictor analysis. Results: Right Atrial Isomerism (RAI) was present in 45 cases and Left Atrial Isomerism (LAI) in 37. The 20-year transplant-free survival was comparable between the groups (RAI vs. LAI, 76% [95% confidence interval, 57-87%] vs. 68% [47-82%], p=0.22). Techniques were extracardiac in 66%, intra-atrial conduit in 9%, lateral tunnel in 18%. More intervention on pulmonary veins occurred in the RAI group. Cardiac position and apicocaval juxtaposition did not influence outcome. The IVC-contralateral PA Fontan was associated with 100% survival, while the IVC-ipsilateral PA Fontan at the side of the cardiac apex showed 67% [34-87%] survival at 20 years. Moderate or severe ventricular dysfunction at 20 years was found in 15% (6-39%) and 0% of RAI and LAI patients among hospital survivors, respectively (p=0.09). In-hospital mortality was higher in heterotaxy (9.8% [5-19%]) compared to TA (1.3% [0.3-5.3%], p<.01) and HLHS (2.8% [1.1-7.3%], p=0.02). There was no in-hospital death after 2000 in any of groups. The 20-year transplant-free survival in heterotaxy (72% [59-82%]) was worse than that in TA (95% [89-97%], p<0.001) but was not significantly different from that in HLHS (80% [69-87%], p=0.11). Reintervention rate at 20 years was significantly higher in heterotaxy (18% [11-29%]) vs. HLHS (8% [4-16%]) (p=0.01). Ventricular dysfunction was a predictor for death (univariate p<0.001). Conclusion: Various routing techniques can be successfully applied to overcome the anatomical challenges of heterotaxy. Although higher in-hospital mortality and reintervention rate were found in heterotaxy in the early era, overall survival post Fontan was similar to that in HLHS. RAI had comparable survival to LAI with greater proportion requiring pulmonary vein intervention at time of Fontan.

The authors have declared no competing interest.

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The study protocol was approved by the Research Ethics Board, the Hospital for Sick Children, Toronto, Ontario, Canada (ID 1000071680).

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