Cardiothoracic Surgical Trials Network (CTSN) Surgical Interventions for Moderate Ischemic Mitral Regurgitation (MMR)

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Accession Number

Study Type
Clinical Trial

Collection Type
Open BioLINCC Study See bottom of this webpage for request information

Study Period
December 2008 – May 2015

NHLBI Division

Dataset(s) Last Updated
December 15, 2023


Commercial Use Data Restrictions No

Data Restrictions Based On Area Of Research No


To evaluate the efficacy and safety of adding mitral-valve repair to coronary-artery bypass grafting for patients with moderate ischemic mitral regurgitation.


People with coronary artery disease (CAD) are at increased risk of having a myocardial infarction. Following an infarction, approximately 50% of people develop a leak in the mitral valve of the heart. This condition is known as ischemic mitral regurgitation and is associated with poor health outcomes. In people with severe mitral valve leakage, the coronary-artery bypass grafting (CABG) procedure and a mitral valve repair procedure are routinely performed together. However, the benefits of adding mitral-valve repair are uncertain in people with moderate mitral valve leakage. This is because mitral-valve repair results in longer durations of aortic cross-clamping and cardiopulmonary bypass that increases perioperative risk. The CTSN-MMR trial was initiated to evaluate the efficacy and safety of adding mitral-valve repair to CABG for patients with CAD and moderate ischemic mitral regurgitation.


Adults with CAD and moderate ischemic mitral regurgitation were eligible for enrollment in the study. Moderate ischemic mitral regurgitation was defined by the presence of at least two of three criteria recommended by the American Society of Echocardiography: an effective regurgitant orifice area of 0.2 to less than 0.4 cm2, a vena contracta width of 3 to less than 7 mm, and a ratio of the mitral regurgitant jet area to the left atrial area of 20% to less than 40%.

A total of 301 patients underwent randomization. 151 patients were assigned to undergo CABG alone and 150 patients were assigned to undergo CABG plus mitral-valve repair.


The CTSN-MMR study was conducted at 26 centers in the Cardiothoracic Surgical Trials Network. Patients were randomly assigned to undergo CABG alone or CABG plus mitral-valve repair. CABG was performed with the use of standard techniques and was supported by cardiopulmonary bypass. The protocol mandated the use of a rigid or semirigid complete annuloplasty ring in patients undergoing mitral-valve repair, unless the ring was contraindicated intraoperatively. The specific ring type, implantation technique, and myocardial-preservation method were at the surgeon’s discretion. All patients received guideline-directed medical therapy by their treating physicians.

The primary end point of the trial was the degree of left ventricular reverse remodeling at 12 months, as measured by means of the left ventricular end-systolic volume index (LVESVI) based on transthoracic echocardiography. Secondary outcomes included major adverse cardiac or cerebrovascular events, rehospitalization, functional status, and quality of life.


In patients with moderate ischemic mitral regurgitation, the addition of mitral-valve repair to CABG, as compared with CABG alone, was not associated with greater improvement in the LVESVI at 1 year after surgery.

Smith PK, Puskas JD, Ascheim DD, et al. Surgical treatment of moderate ischemic mitral regurgitation. N Engl J Med. 2014;371(23):2178-2188. doi:10.1056/NEJMoa1410490

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