Surgical treatment of double-orifice mitral valve in atrioventricular canal defects. Experience in 25 patients.

Double-orifice mitral valve is an uncommon but surgically important condition. The experience in 25 cases of double-orifice mitral valve associated with atrioventricular canal defects was reviewed. This constituted 4.3% of the 581 cases of atrioventricular canal defects operated upon between 1961 and July, 1984. The combined mitral orifice area ranged from 85% to 91% of normal in those patients whose valves were sized intraoperatively. Ten associated cardiac defects were repaired in six patients. Of 23 patients having cleft mitral valve, 21 had partial closure of the cleft. There was one operative death (4.0%), which occurred early in the series in a patient in whom the tissue bridge was severed and massive mitral regurgitation resulted. In the remaining 24 patients the tissue bridge was left intact, and all survived operation. No patient had clinically significant mitral stenosis during a follow-up of 1 to 14 years (mean 4.9 years). Two patients (8%) developed progressive mitral regurgitation and required mitral valve replacement 3 and 11 years postoperatively. One of these patients died and a second death occurred suddenly 2 years following operation. All survivors are in Functional Class I or II. The noncleft orifice of a double-orifice mitral valve usually is competent and rarely requires closure. The cleft, because it constitutes a type of parachute (single papillary muscle) valve, should be closed partially so as to relieve valve incompetence without causing undue stenosis. The incidence of late development of mitral regurgitation is similar to that of atrioventricular canal without double-orifice mitral valve. Repair of atrioventricular canal associated with double-orifice mitral valve can be achieved with a low operative mortality and excellent late results.