An analysis of 24 autopsied cases with supramitral rings.

The supramitral ring is a rare congenital malformation formed by presence of a ridge of connective tissue, usually attached at or above the mitral annulus. The incidence and clinical presentation is highly variable due to difficulty in diagnosis. A review of autopsied congenital heart diseases at our institute over a 17-year-period revealed 24 cases of supramitral ring. These were classified with respect to the morphology of the ridge and the presence of associated cardiac lesions. The ring was found in 1.5% of the autopsied specimens of congenitally malformed hearts, and in 37.5% of those with obstructed left-sided inflow tracts. The majority of the specimens came from children (79.2%). A clinical diagnosis had been made in only two. In one-third of the cases, the ring was associated with incomplete Shone's complex. Varied anomalies were seen in others, chiefly ventricular septal defects. An interesting association was the presence of rheumatic mitral valvar disease, found in 3 cases. There was no difference in the completeness or width of the supramitral ridge in the hearts from those with or without Shone's complex. Circumferential rings were fleshy and stenosing, while incomplete rings had variable locations and stenosis. The presence of a supramitral ring may be underestimated due to association with other cardiac anomalies, both congenital and acquired. Since the ridge need not always produce stenosis, the correct designation would be simply a supramitral ring.