Cardiothoracic Surgical Trials Network: Surgical Treatment of Moderate Ischemic Mitral Regurgitation
In patients with moderate ischemic mitral regurgitation, the addition of mitral-valve repair to coronary-artery bypass grafting (CABG) does not result in a higher degree of left ventricular reverse remodeling, and while mitral-valve repair was associated with a reduced prevalence of moderate or severe mitral regurgitation, it was also associated with an increased number of neurologic events, according to results of the Cardiothoracic Surgical Trials Network trial presented Nov. 18 at AHA 2014 and published simultaneously in the New England Journal of Medicine.
Ischemic mitral regurgitation has long been linked with increased mortality and morbidity. For patients enduring moderate regurgitation, the benefits of adding mitral-valve repair to a coronary-artery bypass grafting (CABG) procedure have remained largely unknown. Seeking a better understanding of the procedure, lead author Peter K. Smith, MD, FACC, Division of Cardiovascular and Thoracic Surgery, Department of Surgery, Duke University Medical Center, Durham, NC, and his colleagues randomly assigned 301 patients with moderate ischemic mitral regurgitation to CABG alone or a combine procedure of CABG plus mitral-valve repair.
At one year the mean left ventricular end-systolic volume index among surviving patients was 46.1+-22.4 ml per square meter of body-surface area in the CABG-alone group and 49.6+-31.5 ml per square meter in the combined procedure group (mean change from baseline, -9.4 and -9.3 ml per square meter, respectively). The rate of death was 6.7 percent and 7.3 percent in the combined procedure and CABG-alone group, respectively (hazard ratio with mitral-valve repair, 0.90; 95 percent confidence interval, 0.38 to 2.12; p=0.81). While the rank-based assessment of the left ventricular end-systolic volume index at one year death showed no significant between-group difference, the addition of mitral-valve repair was associated with a longer bypass time, a longer hospital stay after surgery, and more neurologic events. Severe or moderate mitral regurgitation was shown to be less common in the combined-procedure group than in the CABG-alone group (11.2 percent vs. 31 percent). Finally there were no significant between-group differences in major adverse cardiac or cerebrovascular events, deaths, readmissions, functional status, or quality or life at one year.
Ultimately, the investigators conclude that the routine addition of mitral-valve repair to CABG in this particular patient population may not be warranted. They add that moving forward, “longer-term follow-up may determine whether the lower prevalence of mitral regurgitation translates into a net clinical benefit.”
Thoralf M. Sundt, MD, FACC, Division of Cardiac Surgery, Department of Surgery, Massachusetts General Hospital, Boston, MA, notes in an editorial comment, “this study is a notable contribution. There are precious few prospective, randomized studies addressing valvular heart disease of any kind and even fewer involving surgical therapies. The Cardiothoracic Surgical Trials Network was established to address this deficiency, and this study is proof that it is capable of doing just that. Admittedly, the negative 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 it cannot be said to be entirely unexpected. A number of observational studies over the years have shown much the same. But does this result showing no significant difference between the two surgical approaches put the debate to rest? Unfortunately, I think not.”
According to Kim Eagle, MD, MACC, editor of ACC.org, “since the follow-up is only to one year, and there remained a significantly higher rate of mitral regurgitation in the bypass only group, the jury is still out as to whether mitral repair may have a late favorable effect that this trial has not yet been able to assess.”
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