[Obstruction of the left ventricular outflow tract due to an anomalous muscle bundle and an accessory tissue on the mitral valve associated with mitral stenosis].

This paper details a rare cause of subaortic obstruction, a discrete membrane combined with an anomalous muscle bundle and an accessory tissue on the mitral valve. A 13-year-old boy was referred to our hospital for surgical relief of subaortic obstruction and mitral stenosis. He had received two additional operations, the first was for coarctation of aorta when 5 years old and the second was for discrete subaortic stenosis when 6 years old. Recatheterization at this time revealed an peak systolic gradient of 44 mmHg across the left ventricular outflow tract, and an peak diastolic gradient of 7 mmHg across the mitral valve. An echocardiogram revealed two longitudinally anomalous tissues in the left ventricular outflow tract. Excision of both anomalous tissue and mitral valve replacement were performed. The macroscopic findings and histological reports of the excised specimens showed that one was the accessory mitral valve tissue and another was the anomalous muscle bundle. Intraoperative epicardial echocardiography is beneficial for evaluating the obstructive status of the LV outflow tract before and after excision of the anomalous tissues in this case.