Left ventricular outflow tract obstruction coexisting with ventricular septal defect.

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Abstract
Between Jan. 1973 and March 1982, 13 patients were identified who had, in addition to a ventricular septal defect, a discrete narrowing of the left ventricular outflow tract. Two patients had Fallot''s tetralogy and one a complete atrioventricular canal defect. Two patients previously underwent repair of a juxtaductal coarctation, and 1 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 mm Hg) underwent excision of a fibromuscular shelf. A myotomy was also performed in 6 patients. The left ventricular aortic pressure gradient measured postoperatively was < 15 mm Hg in all but 1 patient. In 7 patients the shelf was excised at the time of closure of the ventricular septal defect; in 4 patients the left ventricular outflow tract obstruction became manifest later. Two further patients not operated on have a discrete narrowing of the left ventricle outflow tract, with a left ventricular aortic pressure gradient of 5 and 30 mm Hg. Two-dimensional echocardiographic assessment of the left ventricular outflow tract was performed in 8 patients and compared with left ventricular angiography. Echocardiography clearly visualized the fibromuscular shelf and its relation to the ventricular septal defect in each case. In 3 of the 8 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 allows recognition of left ventricular outflow tract abnormalities. When a discrete fibromuscular shelf is identified, its excision at the time of closure of the ventricular septal defect is recommended. 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.