CHICAGO – Early results from a randomized trial cast doubt on the benefits of routinely repairing a leaky mitral valve during coronary artery bypass grafting in patients with moderate ischemic mitral regurgitation.
At 1 year, there was no significant difference between patients undergoing CABG alone or CABG plus mitral repair in the primary endpoint of left ventricular reverse modeling, as defined by changes in LV end-systolic volume index (LVESVI) at 1 year (z score 0.50).
Dr. David Adams
Both groups achieved significant reductions in LVESVI, with a median reduction of about 6 mL/m2 from baseline, Dr. Robert Michler, chair of cardiovascular and thoracic surgery at Montefiore Medical Center, New York, reported at the American Heart Association scientific sessions.
At 1 year, patients who underwent CABG and mitral valve repair had significantly less residual moderate or severe mitral regurgitation (11% vs. 31%; P < .001).
On the other hand, the combination procedure was associated with significantly higher rates of any neurologic event (9.6% vs. 3.1%; P = .03), longer cross-clamp (117 vs. 74 minutes) and cardiopulmonary bypass times (163 vs. 106 minutes; P values both < .001), and longer ICU (4.8 vs. 4.0 days; P = .006) and hospital length of stay (11.3 vs. 9.4 days; P = .002), according to the results, also published online (N. Engl. J. Med. 2014 [doi: 10.1056/NEJMoa1410490]).
“The trial did not demonstrate a clinically meaningful advantage to the routine addition of mitral valve repair to CABG,” Dr. Michler said, on behalf of the Cardiothoracic Surgical Trials Network investigators.
The 2014 AHA/American College of Cardiology mitral valve guidelines give a weak class IIb recommendation for mitral valve repair for patients with chronic mitral regurgitation (MR) who are undergoing other cardiac surgery, he noted.
The study evenly randomized 301 patients with moderate ischemic mitral regurgitation to CABG alone or CABG plus valve repair with an undersized ring (average, 28.3 mm for men and 27.1 mm for women).
The mean LVESVI at baseline was 54.8 mL/m2 in the CABG-alone group and 59.6 mL/m2 in the combined procedure group.
Dr. Robert Bonow
At 12 months, mean LVESVIs were 46.1 mL/m2 and 49.6 mL/m2, respectively.
The trial lacked a clinical primary endpoint, and longer follow-up is ongoing to determine whether the lower incidence of moderate or severe MR at 1 year will translate into a net clinical benefit for patients undergoing CABG plus mitral repair, Dr. Michler said.
Designated discussant Dr. David Adams, director of Mount Sinai Hospital’s mitral valve repair reference center in New York, cautioned the audience on the length of the study and called for a full 5 years of follow-up rather than the 2 years as planned.
“Ischemic mitral regurgitation is a disease that hurts you over time. That’s in patients that have had MI, had previous CABG, had attempted mitral valve repair, and had PCI [percutaneous coronary intervention]. So we need much longer term follow-up of this very important data set to really understand its implications,” he said.
In light of roughly half of the patients being in heart failure at baseline, session cochair Dr. Robert Bonow, vice chair of medicine, Northwestern University, Chicago, questioned whether there were differences in outcomes related to changes in baseline ejection fraction (EF) or whether improvement in EF in patients with low EF correlated with reduction in mitral regurgitation with CABG alone.
What is known right now is that mean LVEF increased to the same degree after CABG in both groups, Dr. Michler responded. This was true despite this being a “sick population of patients,” with more than half having diabetes, 50% with heart failure, 20% with renal insufficiency, 10% with prior stroke, and a mean ejection fraction of 40% in both groups.
“What we have yet to identify and plan to explore is the correlation between reverse ventricular remodeling, ejection fraction, and outcome, meaning both the degree of mitral regurgitation and whether there is any signal with respect to repeat hospitalizations, heart failure, or possibly even mortality,” Dr. Michler said.
Both Dr. Michler and Dr. Adams remarked that surgery was extremely safe for the CABG alone and CABG plus MR groups, as reflected by the low mortality at 30 days (2.7% vs. 1.3%) and 1 year (7.3% vs. 6.7%).
The composite endpoint of major adverse cardiac or cerebrovascular events was also similar between groups.
The trial was funded by the National Institutes of Health and the Canadian Institutes for Health Research. Dr. Michler reported grant support from NIH during the conduct of the study. Dr. Adams reported coinventing a mitral valve repair ring.