Subaortic stenosis caused by an unusual fibrous blood-filled cyst of the left ventricle with outflow tract obstruction associated with a ventricular septal defect.

A large blood-filled cyst formed from a fibrous tissue tag of a right ventricular septal aneurysm was successfully resected. This cyst, which was causing subaortic stenosis, was attached to the margin of the closed ventricular septal defect and not to the mitral valve itself nor the papillary muscle of the left ventricle.