EXPERT ANALYSIS FROM THE ANNUAL CARDIOVASCULAR CONFERENCE AT SNOWMASS

SNOWMASS, COLO. (FRONTLINE MEDICAL NEWS) – Percutaneous mitral valve replacement is unlikely to ever catch on in any way remotely approaching that of transcatheter aortic valve replacement for the treatment of aortic stenosis, Blase A. Carabello, MD, predicted at the Annual Cardiovascular Conference at Snowmass.

“We’ve spent $2 billion looking for methods of percutaneous mitral valve replacement, and yet, I have to wonder if that makes any sense,” said Dr. Carabello , professor of medicine and chief of cardiology at East Carolina University in Greenville, N.C.

“If repair is superior to replacement in primary MR [mitral regurgitation], which I think we all agree is true, and you don’t need to get rid of every last molecule of blood going backward across the mitral valve when you’ve got a good left ventricle, then a percutaneous replacement in primary MR would have only the niche of patients who are inoperable and whose leaflets can’t be grabbed by the MitraClip or some new percutaneous device down the road. And, in secondary MR, it doesn’t seem to matter whether you replace or repair the valve, so why not just repair it with a clip?” he argued.

Numerous nonrandomized studies have invariably demonstrated superior survival for surgical repair versus replacement in patients with primary MR.

“There’s never going to be a randomized controlled trial of repair versus replacement; there’s no equipoise there. We all believe that, in primary MR, repair is superior to replacement. There are no data anywhere to suggest the opposite. It’s essentially sacrosanct,” according to the cardiologist.

In contrast, a major randomized trial of surgical repair versus replacement has been conducted in patients with severe secondary MR. This NIH-funded study conducted by the Cardiothoracic Surgical Trials Network found no difference in survival between the two groups ( N Engl J Med. 2016 Jan 28; 374[4]:344-53 ). That’s not a surprising result, Dr. Carabello said, since the underlying cause of this type of valve disease is a sick left ventricle. But, since surgical repair entails less morbidity than replacement – and a percutaneous repair with a leaflet-grasping device such as the MitraClip is simpler and safer than a surgical repair – it seems likely that the future treatment for secondary MR will be a percutaneous device, he said.

That future could depend upon the results of the ongoing COAPT trial (Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy), in which the MitraClip is being studied as an alternative to surgical repair for significant secondary MR. The MitraClip, which doesn’t entail a concomitant annuloplasty, is currently approved by the Food and Drug Administration only for patients with primary, degenerative mitral regurgitation not amenable to surgical repair. But, if COAPT yields positive results, the role of the MitraClip will greatly expand.

An intriguing and poorly understood difference exists in the significance of residual mitral regurgitation following surgical repair as opposed to percutaneous MitraClip repair, Dr. Carabello observed.

“I go to the OR a lot, and I know of no surgeon [who] will leave 2+ MR behind. Most surgeons won’t leave 1+ MR behind. They’ll put the patient back on the pump to repair even mild residual MR, accepting only trace MR or zero before they leave the OR because they know that the best predictor of a failed mitral repair is the presence of residual MR in the OR,” he said.

In contrast, following successful deployment of the MitraClip most patients are left with 1-2+ MR. Yet, as was demonstrated in the 5-year results of the randomized EVEREST II trial (Endovascular Valve Edge-to-Edge Repair Study), this residual MR wasn’t a harbinger of poor outcomes long-term ( J Am Coll Cardiol. 2015 Dec 29;66[25]:2844-54 ).

“You would have expected, with that much residual MR, there would be a perpetually increasing failure rate over time, but that didn’t happen. In Everest II, there was an early failure rate for percutaneous repair, where the MitraClip didn’t work and those patients required surgical mitral valve repair. But, after the first 6 months, the failure rate for the clip was exactly the same as the surgical failure rate, even though, with the clip, you start with more MR to begin with,” the cardiologist noted.

The MitraClip procedure is modeled after the surgical Alfieri double-orifice end-to-end stitch technique, which has been shown to have durable results when performed in conjunction with an annuloplasty ring for primary MR.

“The MitraClip essentially joins the valve in the middle the way the Alfieri stitch does, but it doesn’t appear to behave the same way. Why is that? Maybe the clip does something different than the Alfieri stitch on which it was modeled. Maybe that bar in the middle of the mitral valve does something in terms of scarring or stabilization that we don’t know about yet,” he speculated.

As for the prospects for percutaneous mitral valve replacement, Dr. Carabello said that this type of procedure “is a very difficult thing to do, and so far, has been met with a fair amount of failure. It’ll be very interesting to see what percentage of market share it gets 10 years down the road. My prediction is that, for mitral regurgitation, repair is always going to be it.”

Dr. Carabello reported serving on a data safety monitoring board for Edwards Lifesciences.

bjancin@frontlinemedcom.com

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