DENVER (FRONTLINE MEDICAL NEWS) – Transseptal mitral valve implantation of an off-the-shelf, commercially available TAVR valve in high-surgical-risk patients with a failing surgically implanted mitral ring prosthesis has become a reasonable treatment strategy in light of the interim findings of the ground-breaking MITRAL trial, Mayra E. Guerrero, MD , said at the Transcatheter Cardiovascular Therapeutics annual educational meeting.

Her presentation of the preliminary results of the MITRAL (Mitral Implantation of Transcatheter Valves) trial showed this valve-in-ring (ViR) treatment strategy using the Sapien 3 valve was associated with low 30-day morbidity and mortality rates and impressive symptomatic improvement.

In contrast, another arm of the MITRAL trial showed that placement of the Sapien 3 TAVR valve in high-surgical-risk patients with severe mitral stenosis due to mitral annular calcification (MAC) of their native valve is a treatment strategy that’s not yet ready for prime time, she added at the meeting, which was sponsored by the Cardiovascular Research Foundation.

“Transcatheter mitral valve replacement in MAC is a challenging procedure associated with complications,” Dr. Guerrero observed. “It may become a reasonable alternative for high-surgical-risk patients with favorable anatomy, but techniques require further refinement.”

The ViR arm of the observational multicenter prospective MITRAL trial included 30 patients with extremely high surgical risk and either severe mitral stenosis as defined by a mitral valve area of 1.5 cm2 or less or moderate mitral stenosis plus severe mitral regurgitation. The most common type of failing ring was the Edwards Physio, in nine patients. Access for transcatheter mitral valve replacement (TMVR) was transseptal in 100% of patients.

The technical success rate at exit from the catheterization lab was 70%. The procedural success rate at 30 days was 62%.

Six patients required a second valve. This was mainly because of malpositioning of the first valve with resultant mitral regurgitation; however, this problem became a nonissue as operator experience grew. All six affected patients were alive at 30 days, and four of the six were New York Heart Association (NYHA) functional class I or II.

In-hospital and 30-day mortality rates were low. There was a single cardiovascular death and one noncardiac death in hospital, with no additional deaths through 30 days. No cases of stroke, acute MI, or valve embolization or thrombosis occurred. The mean mitral valve area at 30 days was 2.1 cm2, although three patients still had a mitral valve area of less 1.5 cm2. Three patients experienced acute renal failure requiring hemodialysis. Seventy-five percent of patients had no or trace mitral regurgitation by echocardiography; the rest had mild regurgitation.

Although at baseline more than 60% of the patients were New York Heart Association class III, 10% were class IV, and the rest were class II, at 30 days more than 30% were New York Heart Association class I, 40% were class II, and the rest were class III.

The 30-day all-cause mortality rate of 6.8% in the MITRAL study is roughly half that reported for ViR patients in the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry. Dr. Guerrero attributed this to refined procedural techniques and improved patient selection through the use of CT imaging and echocardiography.

Heart valve design changes, such as a longer inner skirt, might further improve the technical success rate for ViR, according to Dr. Guerrero, an interventional cardiologist at NorthShore University Health System in Evanston, Ill.

Picking the right ring

Given that studies show one-third of recipients of a surgical mitral ring or surgical mitral valve will require a repeat intervention within 10 years, she made a plea to surgeons: “If we are going to be treating patients with valve-in-ring TMVR, that means when surgeons do a repair they should pick a ring that is amenable to a ViR procedure. So don’t use flexible incomplete bands or very rigid rings because those are really difficult to treat later on. We should pick a ring thinking of the future. That ring is going to fail at some point, and when it fails it’s going to make our lives much easier if we’d picked the right ring.”

MAC TMVR needs more work

In the MAC arm of the MITRAL trial, 96 patients were screened so the researchers could find 30 candidates for TMVR. The 61 rejections were for high risk of left ventricular outflow tract obstruction (LVOTO), embolization, or both.

Fourteen patients underwent transseptal TMVR, and one with anatomy unsuitable for a transseptal procedure had a transapical approach. The other 15 patients had a transatrial surgical approach, which allows resection of the anterior leaflet to reduce the risk of LVOTO and placement of sutures to reduce the embolization risk. However, this came at the cost of increased mortality risk: Three of the five in-hospital deaths were in the transatrial TMVR group.

The technical success rate at exit from the cath lab in the MAC patients was 73%, with a 30-day procedural success rate of 46% and a 19% 30-day mortality. Three patients developed severe LVOTO with hemodynamic compromise.

One transseptal and one transapical TMVR were complicated by LVOTO, both treated by bailout alcohol septal ablation. This led Dr. Guerrero and her coinvestigators to the concept of preemptive alcohol septal ablation, which they used in seven patients deemed at high risk for LVOTO an average of 6 weeks prior to transseptal TMVR as a successful risk reduction strategy.

Survival climbing with operator experience

“In the early days of the TMVR MAC registry, the 30-day mortality rate was 37%. It came down to 22% in the middle third of the registry, then about 18% in the final third. Now we’ve got it down in MITRAL to 16.7%, but when you separate the rate in the transseptal versus the transatrial patients, it’s 13% versus 20%. The difference is not statistically significant, but it’s promising, and I think we are making great progress,” Dr. Guerrero said.

Safety and efficacy endpoints in MITRAL will be reported again at 1 year of follow-up.

The MITRAL trial was partially supported by Edwards Lifesciences. Dr. Guerrero reported receiving a research grant from that company and serving as a consultant to Tendyne Holdings/Abbott and on a speakers bureau for Abiomed.

SOURCE: Guerrero M. No abstract.