The midterm and long-term results of the Mustard operation in patients with transposition of the great vessels and dynamic left ventricular outflow tract obstruction.

Eight of 43 patients with transposition of the great vessels (TGV) and either an intact ventricular septum or very small ventricular septal defect were found to have dynamic left ventricular outflow tract obstruction (LVOTO). The preoperative left ventricle-pulmonary artery (LV-PA) pressure gradient ranged between 14 and 60 mm Hg. In 3 patients the pulmonary artery could not be catheterized. They had a left ventricular pressure of 43, 45, and 62 mm Hg, respectively, no evidence of pulmonary vascular disease, and either echocardiographic or angiocardiographic demonstration of LVOTO. The outflow tract was explored in 3 patients at the time of the Mustard operation. Exposure of the LVOT was difficult, particularly in patients less than 6 months of age. A shallow septal myectomy was performed in 1 patient; a thin fibrous endocardial scar was resected in 2; and no procedure was performed in the third. All 8 patients survived and remain asymptomatic 1 to 11 years (mean, 5 years) after operation. The LV-PA pressure gradient has either remained the same or has increased in every patient except 1 in whom there was a slight reduction in the gradient. We conclude that dynamic LVOTO persists after the Mustard operation and is not amenable to direct surgical relief. However, an excellent clinical result can be obtained for up to 11 years after operation.