The perforation of a mitral valve aneurysm is a rare disease which induces acute mitral regurgitation and is usually induced by infective endocarditis; however, in this case report, acute heart failure was caused by a perforated mitral valve aneurysm that was speculated to be due to Libman-Sacks endocarditis with systemic lupus erythematosis and secondary anti-phospholipid syndrome. Mitral valve plasty was performed and thereafter heart failure improved.