Tetralogy of fallot with severe left ventricular outflow tract obstruction due to anomalous attachment of the mitral valve to the ventricular septum

Abstract

Two rare cases of mild tetralogy of Fallot with severe left ventricular outflow tract obstruction are presented. Adherence of the anterior leaflet of the mitral valve to the left ventricular septal surface below the ventricular septal defect resulted in virtual atresia of the left ventricular outflow tract. These 2 cases illustrate a useful distinction between anatomic and physiologic diagnoses: Although anatomic tetralogy was found, physiologic tetralogy was not present because of systemic pulmonary hypertension due to the coexistence of severe left ventricular outflow tract obstruction. Although physiologic double outlet right ventricle was present, anatomic double outlet right ventricle did not exist in view of the presence of aortic-mitral fibrous continuity. The anatomic diagnoses are regarded as the more basic. The nearly complete spontaneous closure of the ventricular septal defect in tetralogy of Fallot shown here is virtually unknown. Occlusion of the left side of the interventricular foramen, instead of the normal right-sided closure, is also infrequent. “Adherent mitral valve” is the most severe form of the atrio-ventricular endocardial cushion malformations that result in left ventricular outflow tract obstruction. Typical fibrous ring subaortic stenosis appears to be a forme fruste of“adherent mitral valve”. These cases demonstrate that atrioventricular “endocardial cushion defect” and common atrioventricular canal are far from synonymous concepts; both patients had an endocardial cushion defect, but neither had a common atrioventricular canal. Since tetralogy of Fallot with congenital left ventricular outflow tract obstruction is a nearly unrecognized syndrome and because the milder forms of such fibrous subaortic stenosis are potentially correctable by surgery, the available clinical, laboratory and pathologic findings are presented.