Congenital mitral valve anomalies in transposition of the great arteries

Abstract

In 165 hearts with transposition of the great arteries, including 16 with a ventricular septal defect and overriding pulmonary trunk and 5 with a so-called posterior transposition, the left ventricle was studied with emphasis on the morphology of the mitral valve. Distinct mitral valve anomalies were found in 36 cases (22 percent), and four categories of anomalies could be identified. Group A Included 16 specimens with a cleft anterior mitral valve leaflet. The cleft was complete or partial. Partial clefts continued as a fibrous cord within the leaflet. In eight cases the cleft was situated posterior or lateral to the pulmonary ostlum; in these cases the left ventricular outflow tract was not narrowed. Severe outflow tract stenosis was present in another eight cases in which the cleft was located anterior to the pulmonary ostlum, usually in combination with a ventricular septal defect, and in four of these specimens there was straddling of the mitral valve.Group B included eight hearts with an abnormal size or position of the mitral valve, or both, the valve being hypoplastic or rotated clockwise, or both. Group C comprised seven hearts showing redundant left ventricular structures involving the mitral valve, among which were anomalous tissue strands, subpulmonary rings and redundant valve tissue. Group D included five specimens with deficient papillary muscles.It is concluded that an abnormal mitral valve is not unusual in hearts with transposition of the great arteries. The findings are notably Important for those patients for whom anatomic surgical correction of the transposition is considered. In comparison with the venous baffle procedure, this operation makes greater demands on the structure of the mitral valve because the pressure in the left ventricle remains at systemic level. Thorough Investigation of mitral valve anatomy and function is necessary before anatomic correction is considered.