Left ventricular outflow tract obstruction coexisting with ventricular septal defect.

Between January 1973 and March 1982, 13 patients have been identified who had in addition to a ventricular septal defect, a discrete narrowing of the left ventricular outflow tract. Two patients had tetralogy of Fallot and one a complete atrioventricular canal defect. Two patients had previously undergone repair of a juxtaductal coarctation and one patient banding of the pulmonary artery. Eleven patients, 10 of whom had left ventricular outflow tract obstruction (mean left ventricular aortic pressure gradient =71 -2±35 3 mmHg) underwent excision of a fibromuscular shelf. A myotomy was performed in addition in six patients. The left ventricular aortic pressure gradient measured postoperatively was less than 15 mmHg in all but one patient. In seven patients the shelfwas excised at the time of closure of the ventricular septal defect, but in four patients the left ventricular outflow tract obstruction became manifest later. Two further patients not operated upon have a discrete narrowing of the left ventricular outflow tract with a left ventricular aortic pressure gradient of 5 and 30 mmHg. Two dimensional echocardiographic assessment of the left ventricular outflow tract was performed in eight patients and compared with left ventricular angiography. Echocardiography clearly visualised the fibromuscular shelf and its relation to the ventricular septal defect in each case. In three of the eight patients the shelf was not seen on the left ventricular angiogram. Assessment of the left ventricular outflow tract in patients with ventricular septal defect by echocardiography will allow recognition of left ventricular outflow tract abnormalities. When a discrete fibromuscular shelf is identified we recommend its excision at the time of closure of the ventricular septal defect. This should be performed even in the absence of a left ventricular aortic pressure gradient to prevent the progressive development of left ventricular outflow tract obstruction and associated myocardial changes.