Development of non-bacterial thrombotic endocarditis after percutaneous transvenous mitral commissurotomy for severely calcified mitral stenosis

We encountered a case of mitral stenosis, complicated with non-bacterial th rombotic endocarditis, that developed after percutaneous transvenous mitral commissurotomy (PTMC). A 71-year-old female Japanese patient had severe co ngestive heart failure and underwent PTMC for critical and severely calcifi ed mitral stenosis. Four weeks later. the echocardiogram demonstrated a hig hly echoic protrusion in the postero-medial commissure of the mitral valve. There was little evidence of inflammation at that time. She had been antic oagulated adequately since she was admitted. The patient underwent replacem ent of the mitral valve. She did not show any evidence of systemic emboliza tion. Microscopic evaluation showed only organized thrombus but no evidence of inflammation in the mitral valve. Silent development of non-bacterial t hrombotic endocarditis after PTMC should be recognized as a rare but potent ially lethal complication of PTMC.