Mitral Repair Can Augment Heart Function in CABG Patients

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In patients with moderate mitral regurgitation (MR) who undergo coronary artery bypass graft (CABG) surgery, the addition of annuloplasty can improve heart function at 1 year. The study results were published online ahead of print in Circulation and presented in an American Heart Association webinar on February 29, 2012.

For the RIME (Randomised Ischemic Mitral Evaluation) trial, K. M. John Chan, BMBS, of Imperial College London (London, United Kingdom), and colleagues enrolled 60 patients who were referred for CABG and had moderate functional ischemic MR (effective regurgitant orifice area 0.2-0.4 cm²). Subjects were randomized to surgery with (n = 30) or without (n = 30) mitral valve repair using complete annuloplasty rings.

At 1-year follow-up, the valve repair group had greater improvement in peak oxygen consumption (VO₂; primary endpoint) as well as greater decreases in left ventricular end systolic volume index (LVESVI), left ventricular sphericity, MR volume, and plasma brain natriuretic peptide (BNP) level compared with the CABG group (table 1).

Table 1. Change in Outcomes from Baseline to 1 Year

The findings “suggest that concomitant CABG and mitral valve annuloplasty should be considered in patients with moderate functional ischemic mitral regurgitation,” Dr. Chan concluded in his presentation.

Approximately 20% of patients develop functional ischemic MR after MI, Dr. Chan reported, adding that even when mild, the condition is associated with increased rates of mortality and hospital admission for heart failure. Combined CABG and mitral valve repair is recommended for severe MR but the optimal treatment of moderate MR is unclear, he said.

Onward to Clinical Practice

Discussant L. Kristin Newby, MD, MHS, of the Duke Clinical Research Institute (Durham, NC), characterized the functional improvement as “really impressive,” but asked about adverse events and procedural complications. In addition, she questioned what the next step should be “in moving this combined technique forward into widespread clinical practice.”

Dr. Chan replied that RIME observed no differences in major complications such as stroke, sepsis, and the need for reoperation due to bleeding. However, patients who underwent the combined procedure had higher use of inotropes, required more blood transfusion (median, 1 unit), and had longer stays in the intensive care unit (median, 1 day) and in the hospital (median, 5 days).

Moving forward, he said, it is important to see whether the improvements are sustained at 5 years and whether the results translate into better survival. Two studies—the MoMIC (Moderate Mitral Regurgitation in CABG Patients) trial being conducted in Denmark and a National Heart, Lung, and Blood Institute-led study slated for completion in 2014—may provide additional information.

But Dr. Chan also pointed out that the 2011 American College of Cardiology and American Heart Association CABG guidelines already give concomitant valve repair for patients with moderate mitral regurgitation a class IIa, level of evidence B recommendation.

The Nuts and Bolts

On behalf of those working in cardiac care units, panel co-chair Elliott Antman, MD, of Harvard Medical School (Boston, MA), asked Dr. Chan what sorts of imaging studies would be most useful for surgeons trying to assess whether patients are good candidates for the dual technique.

Both echocardiography and cardiac MRI are helpful, noted discussant Louis Perrault, MD, PhD, of the Montreal Heart Institute (Montreal, Canada), while Dr. Chan said it is crucial to assess patients both at rest and during exercise. Important procedural factors include using rigid or semi-rigid annuloplasty rings during valve repair and achieving complete revascularization during CABG, he noted.

In short, “these data are informative,” panel co-chair Robert A. Harrington, MD, of the Duke Clinical Research Institute (Durham, NC), said. “They clearly add to the body of knowledge that we have thus far. They [will] probably help us in terms of thinking about our guidelines for the care of this group of patients but . . . we clearly have a bit more work to do.”

Source:

Chan KMJ, Pepper JR. Mitral valve annuloplasty in addition to coronary artery bypass grafting improves functional capacity and promotes reverse left ventricular remodelling: Preliminary results of the Randomised Ischemic Mitral Evaluation trial [abstract]. Circulation. 2012;Epub ahead of print.

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