Membranous supravalvular mitral stenosis: a treatable form of congenital heart disease.

The clinical data, echocardiographic findings, operative anatomy and postoperative follow-up were assessed in 14 patients who had surgery for membranous supravalvular mitral stenosis between 1978 and 1985. The patients ranged in age from 6 weeks to 13 years at the time of operation, and 8 of the 14 had associated mitral valve abnormalities. Other associated lesions included ventricular septal defect (n = 7), coarctation of the aorta (n = 5), left superior vena cava (n = 6), subaortic stenosis (n = 3) and atrial septal defect (n = 1). Twelve of the 14 patients had successful removal of the supravalvular membrane, which was usually adherent to the valve, and 2 patients with associated mitral valve abnormalities underwent mitral valve replacement. There were no operative deaths. Review of preoperative two-dimensional echocardiograms, which were available in 11 patients, revealed two types of membranous supravalvular mitral stenosis in 10 patients. In four of these patients, the membrane was only evident after repeated stop action viewing from a single subcostal or parasternal location. The membrane was never seen in one patient. Eleven patients had follow-up in excess of 1 year, and there was one late death. Eight of the remaining 10 patients are asymptomatic, and 7 have no clinical evidence of residual mitral obstruction. Failure to recognize membranous supravalvular mitral stenosis can result in undue delay of cardiac surgery with resultant cardiopulmonary deterioration. Patients with evidence of left ventricular inflow obstruction should have extensive echocardiographic evaluation in an effort to detect membranous supravalvular mitral stenosis, which may be amenable to surgical repair.