Fate of dynamic left ventricular outflow tract obstruction after anatomic correction of transposition of the great arteries.

Fourteen patients undergoing successful anatomic correction for transposition of the great arteries had subpulmonary gradients of 20 to 120 mm Hg (mean 40) across the left ventricular outflow tract before surgery. Ten patients had an intact ventricular septum, and four had an additional ventricular septal defect. In one patient obstruction was due to ballooning of the septal leaflet of the tricuspid valve through the ventricular septal defect. In the remaining patients obstruction was due to bulging of the interventricular septum plus or minus septal hypertrophy and with or without a fibromuscular shelf. At operation the pulmonary valve was normal and the left ventricular outflow tract was of adequate dimension with no organic obstruction. No attempt at surgical widening was made. After surgery abnormalities revealed by echocardiography were immediately reversed. Routine reinvestigation 6 to 26 months after surgery in 10 patients showed no gradient across the left ventricular outflow tract and normal development of this region.