Longitudinal Data Analysis with stratification:
Stratification by the sex, type of transposition, balloon atrial septostomy and the operating surgeon did not show significant differences. The most notable finding in the stratified longitudinal data display was the rate of drop of the pressure gradient between those who underwent reintervention and those who did not (Figure 8). Longitudinal data analysis with mixed effect modeling showed that the significant variables in relation to the peak pressure gradient following arterial switch operation included: younger age at surgery, complex transposition, and longer bypass time.
As the rate of change of pressure gradient immediately after surgery was the most notable difference between patients based on reintervention. Further testing with proportional hazard modeling for all variables with time-to-reintervention as an outcome with stepwise selection methodology showed that the only predictive preoperative variable for reintervention was the total peak gradient (MPA+RPA+LPA) (p<0.0001). Further analysis with the area under the receiver operating characteristics curve showed that a total peak gradient 55 mmHg or more was a predictor for reintervention with a hazard ratio of 12.