Recognition of developing left ventricular outflow tract obstruction in complete transposition of the great arteries.

In the months following balloon atrial septostomy for complete transposition of the great arteries (TGA), clinical deterioration is often ascribed to closure of the septostomy. Of 16 neonates with TGA, 5 showed early clinical deterioration. Each had an adequate septostomy at operation. Deterioration was characterized clinically by increasing cyanosis and radiographically by progressive diminution in pulmonary vascularity. Subsequent catheterization and axial cineangiography demonstrated that pulmonary flow had decreased, probably secondary to a progressive form of left ventricular outflow tract obstruction (LVOTO) characterized by bulging of the ventricular septum with mitral valve apposition. It is important to recognize this phenomenon as an aid in predicting which children will need early surgical intervention.