RESULTS: Early mortality decreased over the period of study, with no hospital mortality since 2000. Among one year survivors, 10- and 20-year survival was 90% and 72%, respectively. Freedom from reoperation for LVOTO was 87% at 20 years, with no increase in risk among patients having the procedure before 5 years of age. Available late echocardiographic or catheterization data indicated mild or no LVOTO at a median of 14.3 years in a subset of 38 patients. Estimated freedom from major LVOTO at 20 years is bracketed between the estimate of 87% freedom from reoperation for LVOTO at 20 years and the 78% freedom from reoperation for LVOTO or cardiac death by 20 years.