During the past 4 years, five institutions have collaborated in evaluating the efficacy of blade atrial septostomy. The procedure was performed in 52 patients, including 31 with transposition of the great arteries, 10 with mitral atresia, five with tricuspid atresia and six with miscellaneous anomalies. The patient's ages ranged from 1 day to 12 years (mean 13 months). Improvement occurred in 41 of 52 patients (79%). Four patients had an intact interatrial septum, and blade atrial septostomy was successfully performed by a transseptal technique. One patient died from a lacerated left atrial wall; other complications occurred in four patients. Blade atrial septostomy is an effective palliative procedure, even when the interatrial septum is thickened or intact.

Echocardiography was performed in 36 patients with transposition of the great arteries (TGA). Twenty patients were studied before a Mustard operation, 14 patients after operation and two patients both before and after operation. Right ventricular end-diastolic dimension (RVED) was larger than normal in each patient and tended to increase postoperatively. In contrast, the left ventricular end-diastolic dimension (LVED) was significantly reduced postoperatively in all patients. A linear relationship was demonstrated between the ratio of LVED/RVED and the ratio of peak systolic pressures in the left and right ventricles in studies both before and after Mustard operation. Systolic anterior motion of the mitral valve was observed in 18% of peroperative patients and increased to 44% postoperatively. The incidence of fluttering of the mitral valve increased from 50% to 94% after the operation. Abnormal septal motion was found in 39% of cases. Abnormal movement of the mitral valve and of the interventricular septum seems to be related to a reversed pressure relationship in the ventricles. Shifting of the ventricular septum toward the left ventricle and consequent distortion of the left ventricular cavity and mitral valve apparatus may be responsible for the abnormal echocardiographic findings. Serial echocardiographic studies may be useful as a noninvasive tool in the assessment of left ventricular pressure or the status of the pulmonary vascular bed in TGA.