Modifying mitral valve structure concurrently with coronary bypass helps post-MI patients optimize cardiac function and improve functional status

Image: PD/NIH

Key study points:

1. In patients with moderate functional ischemic mitral regurgitation,  CABG plus annuloplasty significantly improved peak myocardial oxygen consumption, a marker of functional status in heart failure, versus CABG alone.

2. Adding annuloplasty was also found to significantly decrease secondary endpoints of left ventricular end-systolic volume, brain natriuretic peptide levels, and volume of mitral regurgitation.

3. Finally, annuloplasty significantly increased length of operation, blood transfusions, and hospital stay. There was no significant difference in 30-day and 1-year mortality rates.

Primer: For those who survive a myocardial infarction, quality of life after the attack is determined largely by how the non-functioning infarcted tissue imposes structural changes on the rest of the heart, a phenomenon called left-ventricular remodeling. The more remodeling that occurs the more pumping of the heart is impaired and the worse the quality of life for the patient. This remodeling can stretch the ventricles so much that an otherwise competent mitral valve will not close properly. Backward flow through the open mitral valve during systole ensues and cardiac function deteriorates even further.

The Randomized Ischemic Mitral Evaluation (RIME) Trial investigated whether repairing mitral valves at the time of coronary artery bypass surgery (CABG) could stop this spiral of remodeling leading to declining heart function and further remodeling, thereby improving outcomes. The study found a significant difference in both primary outcome quantifying functional status and secondary outcomes quantifying regurgitation and remodeling.

Background reading:

  1. Functional, Ischemic Mitral Regurgitation: To Repair or Not to Repair?
  2. Efficacy of adding mitral valve restrictive annuloplasty to CABG in patients with moderate ischemic mitral valve regurgitation.
  3. COUNTERPOINT: Efficacy of adding mitral valve restrictive annuloplasty to coronary artery bypass grafting in patients with moderate ischemic mitral valve regurgitation.

This [randomized controlled] study: involved 73 patients, nearly all with NYHA Class 2 or 3 severity heart failure, and with moderate mitral regurgitation. Patients were randomized to CABG plus MVR (34) or to CABG only (39). 59 of the cohort were assessed at 1-year follow up. Statistical significance was reached for the primary endpoint of peak myocardial oxygen consumption (3.3 mL/kg/min CABG + MVR versus 0.8 mL/kg/min CABG alone; P<0.001), as well as for significant decreases in the secondary endpoints of LV end systolic volume, BNP, and regurgitant volume in patients with CABG + MVR.

In sum: Among patients with moderate ischemic mitral regurgitation, CABG with mitral valve annuloplasty was found to improve functional capacity as measured by peak oxygen consumption when compared to CABG alone in this 73 person randomized controlled trial.

Click to read the study in Circulation

Click to read an accompanying editorial in Circulation

By [GS] and [AH]

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