Iatrogenic injury to the circumflex coronary artery following mitral annuloplasty is a potentially fatal complication. It can be clinically silent or else be responsible for a cardiogenic shock. The diagnosis should be suspected on EKG changes with segmental dysfunction of the lateral wall on the intraoperative echography. The author reports one case whose recognition relied on emergency angiography; the patient was successfully treated by angioplasty and stenting. The management of this complication remains controversial and the various treatment modalities are discussed.