In patients with moderate ischemic mitral regurgitation, adding mitral valve repair to coronary artery bypass graft did not significantly affect the extent of left ventricular remodeling at 2 years, according to a randomized multicenter trial.
Compared with revascularization alone, the combined procedure was associated with a two-thirds lower rate of moderate to severe mitral regurgitation at the end of year 2, reported Dr. Robert Michler at Albert Einstein College of Medicine, New York, together with his associates. But improved durability did not translate to better survival or lower rates of major adverse cardiac and cerebrovascular events, heart failure, or hospital readmissions, they said. Furthermore, adding mitral valve repair to CABG was linked to higher rates of postoperative neurologic events and supraventricular arrhythmias than for CABG alone, the investigators reported at the annual meeting of the American College of Cardiology and simultaneously online April 3 in the New England Journal of Medicine.
Dr. Robert Michler
Surgeons have debated whether to add restrictive mitral annuloplasty to CABG in patients with moderate ischemic mitral regurgitation. The combined approach requires open-heart exposure and longer aortic cross-clamping and cardiopulmonary bypass time, all of which increase perioperative risk, the researchers noted. To explore the risk-benefit balance of these approaches, they randomly assigned 301 patients to either revascularization alone or to the combined procedure, and assessed clinical and echocardiographic outcomes over 2 years (New Engl. J. Med. 2016 April 3 doi: 10.1056/NEJMoa1602003).
At year 1, the arms resembled each other in terms of survival, rates of major adverse cardiac or cerebrovascular events (MACCEs), and left ventricular reverse remodeling, as measured by left ventricular end-systolic volume index (LVESVI), said the investigators. At year 2, the extent of remodeling remained similar between the arms, with mean LVESVIs of 41.2 mL (standard deviation, 20.0 mL) per square meter of body surface area in the CABG-only group and 43.2 mL (SD, 20.6 mL) in the combined procedure group, for a mean decrease from baseline of 14.1 and 14.6 mL, respectively. About two-thirds of improvements in LVESI occurred during year 1 regardless of procedure type, the researchers noted.
About a third of CABG-only patients had moderate to severe mitral regurgitation at 2 years, compared with only 11% of patients who underwent the combined procedure (P less than .001). Patients who had mild or no mitral regurgitation had more than twice the percentage improvement in the global wall motion index and in the inferior-posterior-lateral regional wall motion score, compared with patients with moderate to severe regurgitation. Although both groups improved on several quality-of-life indices, the combined-procedure group scored more than 5 points higher on the Duke Activity Status Index, which measures self-reported exercise capacity. That difference was not only clinically meaningful, but resembled the increase in peak myocardial oxygen consumption in a similar, smaller trial (New Engl. J. Med. 2016 Jan. 28 doi: 10.1056/NEJMoa151291), the investigators noted.
However, mortality rates were similar between the arms at 2 years – 10.6% for CABG only and 10% for the combined procedure, for a non-significant hazard ratio of 0.9. Likewise, rates of heart failure and other serious adverse events were similar between the arms, while the combined-procedure arm had more than three times more postoperative neurologic events and more than twice as many occurrences of supraventricular arrhythmia. Therefore, treatment choice requires “balancing the risks of adverse perioperative events against the uncertain benefits of a lower incidence of postoperative moderate or severe mitral regurgitation,” said the researchers. “Effective revascularization, as reflected in improved regional and global left ventricular function, plays an important role independent of mitral valve repair.”
The National Institutes of Health and the Canadian Institutes of Health Research funded the study. Disclosures were reported separately at nejm.org.