I surveyed our echocardiographic database of the years between 1998 and 2012 for congenital abnormalities of the mitral valve in patients over 14 years. A total of 249 patients with mitral valve abnormalities were identified. Abnormalities included clefts in the mitral valve in 58 patients, double orifice of the mitral valve in 19, mitral stenosis with two papillary muscles in 72, and mitral stenosis with one papillary muscle in 51 patients. Supravalvar rings were found in 35 patients with a single papillary muscle, and mitral stenoses with two papillary muscles were found in 22 patients. Mitral prolapse occurred in 44 patients and mitral valvar straddle in five patients. The patients were evaluated by all modalities of ultrasound available over the course of time. Although some lesions were isolated, there were many lesions in which more than one mitral deformity presented in the same patient. The patients are presented showing anatomical correlation with autopsy specimens, some of which came from the patients in this series, and others matched to show correlative anatomy. These lesions remain rare as a group and continue to have high morbidity and mortality.

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.

Balloon dilation was attempted in seven symptomatic patients with congenital mitral stenosis aged 7.6±5.3 years. Of the five patients with typical mitral stenosis, four underwent successful dilation with decrease of the mean left atrial pressure and the gradient across the mitral valve and increases in the area of the valve of 127±43 and 85±16%, respectively, as demonstrated hemodynamically or by Doppler echocardiography. In the patient in whom the procedure was unsuccessful, a small child with recurrent pulmonary edema, death occurred during the procedure as a consequence of vasovagal reaction. In the other two patients, one with a parachute-like mitral valve and the other with Shone's syndrome, severe pulmonary hypertension and reversal of the shunt through a patent arterial duct, it was not possible to dilate the valve. In the patient with Shone's syndrome, nonetheless, palliation was achieved by balloon angioplasty of the aortic coarctation and by creation of an atrial septal defect. The patients undergoing dilation remained symptom-free during follow-up and mantained the increase in valvar area as judged by Doppler studies and, in one patient, also by cardiac catheterization. A residual atrial septal defect closed spontaneously in three patients. We conclude that balloon dilation of congenital mitral stenosis is an effective alternative to surgery in patients with typical mitral stenosis. Cross-sectional echocardiography plays an important role in defining valvar morphology and selection of patients. The procedure is not without risk, especially in very sick patients but satisfactory results are long-lasting.