[A case of subaortic stenosis due to parashute accessory mitral valve tissue].

An 11-year-old boy with subaortic stenosis due to parashute accessory mitral valve tissue was treated successfully with surgery. He had a mild left ventricular-aortic pressure gradient associated with mild aortic regurgitation. The abnormal subaortic tissue was attached to the anterior leaflet of the mitral valve and was complicated with discrete subaortic stenosis. This tissue had five chordae connecting to the anterior papillary muscle and the anterior leaflet of the mitral valve. By resection of this accessory tissue and the part of the septal discrete stenotic tissue, stenosis of the left ventricular outflow tract was relieved completely.