Evolution of Risk Factors Influencing Early Mortality of the Arterial Switch Operation

Objectives: The present study was undertaken to determine the independent risk factors for early mortality in the current era after arterial switch operation (ASO).

Background: Prior reports on factors affecting outcome of the ASO demonstrated that abnormal coronary arterial patterns were associated with increased risk of early mortality. As diagnostic, surgical and perioperative management techniques continue to evolve, the risk factors for the ASO may have changed.

Methods: All patients who underwent the ASO at Children's Hospital, Boston between January 1, 1992 and December 31, 1996 were included. Hospital charts, echocardiographic and cardiac catheterization data and operative reports of all patients were reviewed. Demographics and preoperative, intraoperative and postoperative variables were recorded.

Results: Of the 223 patients included in the study (median age at ASO = 6 days and median weight = 3.5 kg), 26 patients had aortic arch obstruction or interruption, 12 had Taussig-Bing anomaly, 12 had multiple ventricular septal defects, 8 had right ventricular hypoplasia and 6 were premature. There were 16 early deaths (7%), with 3 deaths in the 109 patients considered "low risk" (2.7%). Coronary artery pattern was not associated with an increased risk of death. Compared with usual coronary anatomy pattern, however, inverted coronary patterns and single right coronary patterns were associated with increased incidence of delayed sternal closure (p = 0.003) and longer duration of mechanical ventilation (p = 0.008). In a multivariate logistic regression model using only preoperative variables, aortic arch repair at a separate procedure before ASO and smaller birth weight were independent predictors of early mortality. In a second model that included both pre- and intraoperative variables, circulatory arrest time and right ventricular hypoplasia were independent predictors of early death.

Conclusions: The ASO can be performed in the current era without excess early mortality related to uncommon coronary artery patterns. Aortic arch repair before ASO, right ventricular hypoplasia, lower birth weight and longer intraoperative support continue to be independent risk factors for early mortality after the ASO.