Diagnosis and surgical treatment of accessory mitral valve with associated congenital heart disease

Accessory mitral valve (AcMV) is a rare cardiac anomaly that may possibly cause left ventricular outflow tract (LVOT) obstruction. Five patients who underwent surgical resection of AcMV were reported. All these patients had associated cardiac anomalies, which include transposition of great arteries (TGA) in two cases, ventricular septal defect (VSD) in one, double outlet right ventricle (DORV) in one and membranous septal aneurysm (MSA) in one. Age at operation ranged from 23 days to 22 months. In these cases preoperative pressure gradient across the LVOT ranged from 10 to 35 mmHg. Resection of AcMV was performed together with radical operation for associated anomalies in all the patients. Approach for resection of AcMV consisted of trans-ventricular septum method in 3 patients of VSD, DORV or MSA and trans-pulmonary artery method in 2 cases of TGA. There was no operative death. The postoperative pressure gradient across the LVOT ranged from 0 to 13 mmHg. Two dimensional echocardiography was essential for the accurate preoperative diagnosis of AcMV in 4 out of the 5 patients. The trans-ventricular septum method, when the large VSD was present, for resection of AcMV was found to be quite useful especially for neonates in order to obtain an excellent operative field, as compared with the conventional method.