Echocardiographic classification of complete atrioventricular canal defects.

M-mode echocardiographic records of 26 patients with surgically proven complete atrioventricular canal defect were reviewed. Fragmentation of the interventricular septum and anterior displacement of the mitral annulus into the left ventricular outflow tract were noted in all patients. In 25 of 26 a common atrioventricular valve leaflet echo could be identified in the left ventricular outflow tract at the area of the left ventricle demonstrated separate "mitral" and "tricuspid" contributions to atrioventricular valve echoes in all 13 patients with type A defect, and a single common atrioventricular valve leaflet in 10 of 11 patients with type C complete atrioventricular canal. Two patients with type B defect had findings intermediate between these two patterns. M-mode echocardiography presumptively diagnosed complete atrioventricular canal in all 26 patients and diagnosis was definitive in 25 of 26. In addition, echocardiographic atrioventricular valve patterns permitted anatomic classification in the large majority of cases.