Echocardiographic Features of Subpulmonic Obstruction in Transposition of the Great Vessels

Abstract

Eleven patients with transposition of the great vessels (TGV) and subpulmonic (left ventricular outflow) obstruction documented by cardiac catheterization/ angiography were studied by echocardiography. Ten showed prolonged mitral-septal apposition in diastole indicative of a narrow left ventricular outflow tract. In addition, 5 patients showed systolic anterior movements (SAMs) of the anterior mitral leaflet resembling those observed in hypertrophic subaortic stenosis. The SAMs were large in 3 patients and may have accentuated the outflow obstruction. Additional evidence for this was provided by the tendency of the pulmonic valve towards closure with the onset of mitral SAMs. A comparison group of 21 patients with TGV and no outflow obstruction did not show these features. Echocardiography appears to be useful in the diagnosis of subpulmonic muscular obstruction in TGV. Demonstration of definite mitral SAMs in some patients suggests the presence of associated functional obstruction of the type seen in hypertrophic subaortic stenosis.