ObjectiveWe sought to identify the impact of pulmonary artery size on outcomes after nonfenestrated total cavopulmonary connection. In a subgroup of patients with right-sided bidirectional cavopulmonary shunt, the impact of each branch pulmonary artery size was individually determined. MethodsThe medical records of all patients who underwent nonfenestrated total cavopulmonary connection between 2009 and 2021 were reviewed. The pulmonary artery index was calculated using angiography before the operation. ResultsA total of 247 patients were included in this study. A right-sided bidirectional cavopulmonary shunt was performed in 217 patients (88%). Median pulmonary artery index was 162 (133-207) mm2/m2 before total cavopulmonary connection. Chylothorax occurred in 55 patients (22%). Pulmonary artery index was an independent factor for chylothorax (odds ratio, 0.98, 95% confidence interval, 0.97-0.99, P < .001) with a cutoff value of 170 mm2/m2. In a subgroup of patients with right-sided bidirectional cavopulmonary shunt, the left pulmonary artery index was identified as an independent risk factor for longer stay in the intensive care unit (coefficient B –0.02, 95% confidence interval, –0.04 to –0.002, P = .034) and for adverse events (hazard ratio, 0.98, 95% confidence interval, 0.96-0.99, P = .011) with a cutoff value of 56 mm2/m2. ConclusionsThe pulmonary artery index is significantly associated with the occurrence of chylothorax after nonfenestrated total cavopulmonary connection with a cutoff value of 170 mm2/m2. In patients with right-sided bidirectional cavopulmonary shunt, left pulmonary artery index has a significant predictive value for longer stay in the intensive care unit and adverse events with a cutoff value of 56 mm2/m2.