Background: This study was undertaken to identify risk factors for early mortality following the Norwood procedure for hypoplastic left heart syndrome (HLHS) and develop a predictive risk model to monitor clinical performance.
Methods and results: Between December 1992 and June 2004, 333 patients with HLHS underwent a Norwood procedure at a single institution. The early mortality was 29% (n=95). Estimated early mortality improved progressively and was 10% at the end of the series. Multivariable analysis identified that body surface area at operation, size of the ascending aorta, preoperative right ventricular function and source of pulmonary blood flow established at operation were risk factors for early mortality (P<0.05). These variables were included in a preoperative risk model. The duration of cardiopulmonary support was an independent risk factor, which was included in a separate operative risk model. The performance of the risk models was evaluated by goodness-of-fit analyses, using the Hosmer-Lemeshow test and receiver operating characteristic (ROC) curve. Both models were well calibrated across all deciles (P=0.64, P=0.77) and discriminated moderately well. The area under the ROC curve was 0.71 for Model 1 and 0.75 for Model 2. Risk adjustment broadly accounted for the variation in early mortality observed during this series.
Conclusions: Patient-related and predetermined operative variables have a major influence on the early outcome following the Norwood procedure for HLHS. The identification of these risk factors allows the risk of early mortality to be calculated. This information could be applied as part of a risk-adjusted performance-monitoring system to enable early identification of meaningful changes in practice.