Unusual mitral valve abnormalities complicating surgical repair of endocardial cushion defects.

A review of 155 cases of surgically repaired endocardial cushion defects revealed 16 patients (10%) with additional unusual mitral valve abnormalities that complicated the surgical procedure. Eight patients had accessory mitral valve tissue that connected the anterior and posterior leaflets to form a double-orifice valve (Group I). In four (50%), the lesion was associated with intermediate atrioventricular canal and small left ventricle; all four died following repair. In the other four, it was associated with ostium primum defect; all survived and are well. A single papillary muscle in the left ventricle was present in six patients (Group II). Two had intermediate atrioventricular canal and both died postoperatively. The other four had complete endocardial cushion defect and three are well following the operation. Perforation of the valve leaflets was present in two patients with ostium primum (Group III). Both patients are well postoperatively. Modification of the surgical technique is required to effect satisfactory repair. The bridge connecting the posterior and anterior leaflets of the mitral valve should be left undisturbed. Otherwise, severe regurgitation may result. In patients with single papillary muscle and complete atrioventricular canal, repair may be accomplished by borrowing from the tricuspid portion of the anterior leaflet, rotating that part posteriorly, and partially closing the cleft. Small perforations of the mitral leaflet do not require closure and do not result in regurgitation. Echocardiographic and angiographic delineation of these abnormalities and thorough intraoperative exploration are important in avoiding pitfalls at the time of repair.