Interactive pathologies of mitral prolapse and true membranous septal aneurysm with a valve-like structure

A 70-year-old man was admitted to our hospital for surgical treatment of mitral insufficiency. A preoperative echocardiogram revealed a prolapsed anterior mitral leaflet, membranous septal aneurysm (MSA), and unusual chordae extending from the ventricular septum to the anterior mitral leaflet (Movies I and II in the online-only Data Supplement). In surgery, the aneurysm was examined through the tricuspid valve before the heart was arrested (Figure 1A). On further inspection, when the MSA was pushed with forceps, a large quantity of blood suddenly …