EXPERT ANALYSIS FROM THE CARDIOVASCULAR CONFERENCE AT SNOWMASS
SNOWMASS, COLO. (FRONTLINE MEDICAL NEWS) – A clear message from the first-ever randomized trial of surgical mitral valve repair versus replacement for patients with severe ischemic mitral regurgitation is that replacement should be utilized more liberally, Dr. Michael J. Mack said at the Annual Cardiovascular Conference at Snowmass.
The results of prosthetic valve implantation proved far more durable than repair. At 2 years of follow-up in this 251-patient multicenter trial conducted by the Cardiothoracic Surgical Trials Network (CSTN), the incidence of recurrent moderate or severe mitral regurgitation was just 3.8% in the valve replacement group, compared with 58.8% with repair via restrictive annuloplasty. As a result, the repair group had significantly more heart failure–related adverse events and cardiovascular hospitalizations and a lower rate of clinically meaningful improvement in quality of life scores, noted Dr. Mack, an investigator in the trial and medical director of the Baylor Health Care System in Plano, Tex.
“I think surgical mitral valve replacement has had a bad name over the years, and one of the reasons is because of the worse left ventricular function afterwards. However, that was a casualty of excising the mitral valve and the subvalvular apparatus, causing atrial-ventricular disconnection. We’ve gotten smarter about this. The techniques we now use are valve sparing,” the cardiothoracic surgeon said.
He was quick to add, however, that the CSTN study results are by no means the death knell for restrictive mitral annuloplasty. Indeed, participants in the mitral valve repair group who didn’t develop recurrent regurgitation actually experienced significant positive reverse remodeling as reflected by improvement in their left ventricular end-systolic volume index, the primary endpoint of the study ( N Engl J Med. 2016;374:344-35 ).
The key to successful outcomes in mitral valve repair is to save the procedure for patients who are unlikely to develop recurrent regurgitation. And a substudy of the CTSN trial led by Dr. Irving L. Kron , professor of surgery at the University of Virginia, Charlottesville, provides practical guidance on that score. The investigators conducted a logistic regression analysis of the mitral valve repair group’s baseline echocardiographic and clinical characteristics and identified a collection of strong predictors of recurrent regurgitation within 2 years ( J Thorac Cardiovasc Surg. 2015 Mar;149[3]:752-61 ).
“The bottom line is, the more tethering you have of the mitral valve leaflets, the more likely you are to have recurrent mitral regurgitation after mitral valve annuloplasty,” Dr. Mack said.
The predictors of recurrent regurgitation included a coaptation depth greater than 10 mm, a posterior leaflet angle in excess of 45 degrees, a distal anterior leaflet angle greater than 25 degrees, inferior basal aneurysm, mitral annular calcification, and a left ventricular end diastolic diameter greater than 65 mm, as well as other indices of advanced left ventricular remodeling.
No or only mild annular dilation, as occurs, for example, in patients whose mitral regurgitation is caused by atrial fibrillation, is another independent predictor of recurrent regurgitation post repair.
“Shrinking the annulus isn’t going to make a difference if the annulus wasn’t dilated to begin with,” the surgeon observed. “If surgery is performed, we now know those patients who are most likely to recur – and they should have mitral valve replacement. If those factors are not present, then repair is still a viable option,” according to Dr. Mack.
That being said, it’s still not known whether correcting severe ischemic mitral regurgitation prolongs life or improves quality of life long term, compared with guideline-directed medical therapy, he stressed.
“Secondary mitral regurgitation is a disease of the left ventricle, not the mitral valve. So it’s possible that mitral regurgitation reduction has no benefit because the regurgitation is a surrogate marker not causally related to outcome. I don’t think so, but it is a possibility,” Dr. Mack conceded.
This is a clinically important unresolved question because secondary mitral regurgitation is extremely common. In a retrospective echocardiographic study of 558 heart failure patients with a left ventricular ejection fraction of 35% or less and class III-IV symptoms, 90% of them had some degree of mitral regurgitation ( J Card Fail. 2004 Aug;10[4]:285-91 ).
Together with Columbia University cardiologist Dr. Gregg W. Stone, Dr. Mack is coprincipal investigator of the COAPT (Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation) trial, which is expected to provide an answer to this key question. The multicenter U.S. study involves a planned 420 patients with severely symptomatic secondary mitral regurgitation who are deemed at prohibitive risk for surgery. They are to be randomized to guideline-directed medical therapy with or without transcatheter mitral valve repair using the MitraClip device. Enrollment should be completed by May, with initial results available in late 2017.
Dr. Mack reported receiving research grants from Abbott Vascular, which is sponsoring the COAPT trial, as well as from Edwards Lifesciences.
