A predictive model for neurodevelopmental outcome after the Norwood procedure

Abstract

Neurodevelopmental outcomes after the Norwood procedure for single right ventricular lesions are worse than those in the normal population. It would be valuable to identify which patients at the time of Norwood discharge are at greatest risk for neurodevelopmental impairment later in childhood. As such, this study sought to construct and validate a model to predict poor neurodevelopmental outcome using variables readily available to the clinician. Using data from the 14 month neurodevelopmental outcome of the Single-Ventricle Reconstruction (SVR) trial, a classification and regression tree (CART) analysis model was developed to predict severe neurodevelopmental impairment, defined as a Psychomotor Development Index (PDI) score lower than 70 on the Bayley Scales of Infant Development-II. The model then was validated using data from subjects enrolled in the Infant Single Ventricle (ISV) trial. The PDI scores were lower than 70 for 138 (44 %) of 313 subjects. Predictors of a PDI lower than 70 were post-Norwood intensive care unit (ICU) stay longer than 46 days, genetic syndrome or other anomalies, birth weight less than 2.7 kg, additional cardiac surgical procedures, and use of five or more medications at hospital discharge. Using these risk factors, the CART model correctly identified 75 % of SVR subjects with a PDI lower than 70. When the CART model was applied to 70 subjects from the ISV trial, the correct classification rate was 67 %. This model of variables from the Norwood hospitalization can help to identify infants at risk for neurodevelopmental impairment. However, given the overall high prevalence of neurodevelopmental impairment and the fact that nearly one third of severely affected children would not have been identified by these risk factors, close surveillance and assessment for early intervention services are warranted for all infants after the Norwood procedure.

Figure 1

Classification analysis for PDI <70 at 14 months of age. Shaded boxes indicate terminal nodes. A terminal node occurs when it is not possible to find any variable that separates this subsample into any more homogeneous subgroups. CART terminates disaggregation at this level.