Novel Device Shows Promise in Severe Mitral Regurgitation

Patrice Wendling

November 07, 2017

DENVER, CO - More than a decade since its inception in the lab, 6-month outcomes suggest a minimally invasive chordal implantation system may be one step closer to reality for patients with severe degenerative mitral regurgitation (MR).

Among 26 patients treated with the Harpoon device (Harpoon Medical) and evaluable at 6 months, MR was reduced to mild or less in 85% of patients, moderate in 8%, and severe in 8% in the Mitral Transapical Neochordal Echo-guided Repair (TRACER) trial[1], which was designed for CE Mark approval in Europe.

"We believe for physicians this is going to demystify mitral-valve repair and is going to turn the low-volume mitral-valve surgeon into a high-quality mitral-valve repair surgeon," principal investigator and device inventor Dr James Gammie (University of Maryland School of Medicine, Baltimore) said at a press briefing at TCT 2017.

"We also think it will encourage earlier referral to intervention before patients develop afib and MR ventricular dysfunction. Finally, it will also address the high-risk patient population who otherwise wouldn't be referred for intervention," he added.

The Harpoon device is designed to enable off-pump MR repair. It uses a 21-gauge needle prewrapped with polytetrafluoroethylene (ePTFE) knotted sutures, which are anchored under echocardiographic guidance to the prolapsed mitral leaflet and adjusted to the correct length to maximize coaptation.

"The heart remains beating and loaded, so you can really assess in real time and in real physiology whether you've secured the repair. So I think this is a potentially tremendous step forward, and I can't wait to see it, say, in randomized comparison with surgical repair," Dr Dean Kereiakes (Christ Hospital Heart and Vascular Center, Cincinnati, OH), who was not involved with the study, commented for | Medscape Cardiology.

In their initial clinical experience with the investigational device, the researchers reported 100% success among 11 patients with severe MR[2].

In TRACER, the technical success rate was 93% among 30 consecutive patients with severe MR and isolated posterior leaflet prolapse. The patients were prospectively enrolled from six European sites. A mean of 3.9 pairs of ePTFE cords were implanted, with a mean procedure time of 125 minutes, according to the study, which was simultaneously published in the Journal of the American College of Cardiology.

Two cases required conversion to conventional open mitral surgery because of suboptimal imaging equipment that prevented accurate placement of the knots.

One patient required conventional cardiac surgery on postoperative day 27 for recurrent severe MR caused by infective endocarditis related to unreported dental caries.

At 30-day follow-up, 89% of patients (23/27) had mild or less-than-mild MR, and none had severe MR. During the formal presentation, questions were raised about these MR rates and about the 8% severe MR rate at 6 months.

"The data will tell over time, but I can tell you we have a number of patients now out to 2 years with really stable and durable results," Gammie told reporters. "The few patients that we saw progression on had reasons."

These included the two early cases with imaging dysfunction; a third case with dense plaque below the mitral leaflet that prevented the leaflet from being repositioned into the ventricle; and a fourth case, in which perforation of the leaflet resulted in only a single knot being placed. The patient developed moderate MR at 30 days that progressed to severe MR at 6 months, which was successfully treated with 3 pairs of ePTFE cords and an annuloplasty ring at 8 months.

Annuloplasty Effect Sans Ring

One of the concerns raised about the Harpoon system is the lack of an annuloplasty ring, but Gammie observed that the procedure translocates the posterior leaflet not only toward the apex but also toward the anterior surface of the heart. "As a result, it creates a broad annuloplasty effect that we believe contributes to the mid-term stability of the repair," he said.

At 6 months, there was evidence of left ventricular remodeling, which included a 25% reduction from baseline in end-diastolic volume, a 20% reduction in anterior-to-posterior annular diameter, and a 30% reduction in mitral annular area (P<0.001 for all). Gradients were low at a mean of 1.5 mm Hg.

"People have always thought there was some need for annular reduction in these patients, and it's intriguing," Kereiakes commented. "A 20% reduction in annular diameter is very nice and will help long term."

During follow-up, there was no evidence that implantation resulted in damage to the leaflet, nor were there any reports of death, stroke, MI, or renal failure. New postoperative atrial fibrillation occurred in two patients, and atrial flutter occurred in one. For context, about 20% to 30% of patients who undergo conventional surgical mitral repair require subsequent valve replacement, Gammie said.

MitraClip vs Harpoon

Responding to a question about how one would choose between the MitraClip  (Abbott Vascular) transcatheter mitral-valve system and the Harpoon system for their MR patients, Gammie said his institution doesn't treat degenerative MR with the MitraClip because "of the FDA approval for the device as well as our impression that the results of MitraClip for [degenerative mitral regurgitation] DMR that we feel aren't that good over the long term."

Also, "These patients are young and otherwise healthy. We want to give them a lifetime of repair," he added.

Still, all sites in the TRACER study were also MitraClip sites, and the surgeons had experience working closely with the echocardiographer as part of a team―an "absolutely crucial" aspect of the Harpoon procedure, said Gammie, who suggested the novel technology is not quite ready for use by interventionalists.

"I will point out that our device's level of stress from a surface standpoint is a lot lower because it's a 14-French valve introducer, so it's really small compared with a 35-French device, and the level of stress is lower, but it is a surgery," he remarked. "Someday, some bold interventionalist may do this, but I wish them well in fixing the ventricle if they get into trouble."

On the basis of the results, Gammie expects the Harpoon device to receive CE Mark approval and sees no reason why anterior leaflet patients, who were excluded from the study, can't be treated with the technology.

Harpoon Medical, which received an infusion of funds from Edwards Lifesciences in 2015 with an option to purchase the company, has had several discussions with the FDA and anticipates it "will be required to do a randomized trial against conventional surgery in the US," likely involving a keyhole thorascopic approach, Gammie said.

"In the longer term, it would be really great to develop a repair for [functional mitral regurgitation] FMR that works really well, but we don't have that yet. That's a big black box; we've got some ideas but we haven't done that yet," Gammie said in an interview.

In the meantime, he said the COAPT trial, which pits the MitraClip against medical therapy in heart-failure patients with FMR, should really affect the field, but "it's a trial of a device that's pretty good at fixing MR but not really great at fixing MR.

"The big question is, does fixing MR in FMR help the patients?" Gammie added. "FMR isn't one disease, it's multiple diseases, and probably there are some patients where fixing the mitral really helps them a lot, and there are others where it probably won't help them at all. I think we're going to need to do a lot of trials to figure out who we can help and how."

The study was funded by Harpoon Medical. Gammie reported consulting fees/honoraria from Edwards Lifesciences and major stock/equity in Harpoon Medical. Disclosures for the coauthors are listed in the paper.

Follow Patrice Wendling on Twitter:@pwendl. For more from | Medscape Cardiology, follow us onTwitter and Facebook.


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