No Advantage Seen to Surgical Repair Added to CABG for Ischemic Mitral Regurgitation

November 18, 2014

CHICAGO, IL — Patients with moderate ischemic mitral regurgitation undergoing CABG did not show any clinical benefit from adding in mitral-valve repair to the surgery and had a higher rate of neurological adverse effects, according to 1-year results of the largest trial to look at this question to date[1,2].

Dr Robert Michler

Although the patients who received the repair, which included insertion of an annuloplasty ring, did show less mitral regurgitation compared with those who had CABG alone, this did not translate into a reduction in clinical outcomes at 1 year.

In addition, these patients showed an increase in neurological effects, probably related to the longer time on bypass required for the valve-repair procedure.

Presenting the data at the American Heart Association (AHA) 2014 Scientific Sessions, Dr Robert Michler (Montefiore Medical Center–Albert Einstein College of Medicine, New York, NY) concluded: "Bottom line is you don't need to ring it."

Longer-term Follow-up Needed

But he added, "Longer-term follow-up is needed to see whether the reduction in mitral regurgitation in the repair group will translate into better clinical outcomes in certain subgroups in the long term."

Dr Timothy Gardner

Commenting to heartwire , study author Dr Timothy Gardner (Christiana Care Health System, Newark, DE) said: "We can't say for sure that repair isn't worth doing from these results. It's not that black and white. It looks like there are some patients for whom mitral repair under these circumstances would be appropriate, but we haven't sorted that out yet. We need to do a subgroup analysis. We have only 1-year follow-up so far, and we are being cautious about the results. We need much longer-term follow-up to know anything for sure."

While introducing the presentation, Michler explained that about half of the one million MI patients in the United States develop ischemic mitral regurgitation each year, and moderate regurgitation occurs in more than 10%. Many patients with ischemic mitral regurgitation require surgical revascularization for multivessel CAD, at which time surgeons often consider concomitant mitral-valve repair. But the evidence of whether the additional repair is worthwhile is uncertain, and previous study results have been conflicting.

The current Surgical Interventions for Moderate Ischemic Mitral Regurgitation (IMR) study, supported by the US National Heart, Lung, and Blood Institute (NHLBI), was conducted to answer this question and included more patients and centers than previous studies.

In the study, 301 patients with multivessel CAD and moderate ischemic mitral regurgitation were randomized to CABG alone or with mitral-valve repair.

At 1 year there was no difference between groups in the primary end point of left ventricular end systolic volume index (LVESVI) or the secondary composite end point of major adverse cardiac or cerebrovascular events (death, stroke, subsequent mitral-valve surgery, hospitalization for heart failure, and an increase of one or more NYHA heart failure classes).

The addition of mitral-valve repair was associated with a 57-minute longer bypass time (163 vs 106 min), longer hospital stay after surgery, more serious neurological events (including stroke, transient ischemic attack, and metabolic encephalopathy), and higher rate of AF. However, moderate or severe mitral regurgitation was less common in the combined-procedure than the CABG-alone group.

CABG Alone vs CABG Plus Valve Repair: 1-Year Results

Outcome CABG alone CABG plus repair P
Left ventricular end systolic volume index (mL/mm3) 46.1 49.6
Death (%) 7.3 6.7 0.83
Composite clinical end point* (%) 25.2 25.3 0.97
Neurological events (%) 3.1 9.6 0.03
Supraventricular arrhythmia (%) 8.4 17.8 0.03
Moderate/severe mitral regurgitation (%) 31.0 11.2 <0.001
*Major adverse cardiac or cerebrovascular events (death, stroke, subsequent mitral-valve surgery, hospitalization for heart failure, and an increase of one or more NYHA heart failure classes)

The study was published in the New England Journal of Medicine to coincide with its presentation at the AHA meeting. In an accompanying editorial[3], Dr Thoralf M Sundt (Massachusetts General Hospital, Boston) says the result is "disappointing to the surgeon hoping to 'fix the problem' directly and is counter to the popular surgical trend to encourage valvular intervention."

But he points out that ischemic mitral regurgitation may occur as a result of active reversible ischemia or a completed infarction, and this study included both types of patients. He writes: "It would come as no surprise to discover that ventricular dysfunction due to reversible ischemia may be correctable by revascularization alone, whereas that due to infarction would probably not be. Inclusion of patients with either pathologic feature will muddle the results of any study intended to distinguish the roles of these interventions."

The study was conducted as part of NHLBI Cardiothoracic Surgical Trials Network and was cofunded by the National Institute for Neurological Diseases and Stroke and Canadian Institutes for Health Research. Michler reports grant support from the National Institutes of Health/NHLBI during the study. Gardner reports no relevant financial relationships. Disclosures for the other coauthors are listed on www.nejm.org. Sundt reports personal fees from Thrasos.

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