Transapical Valve Replacement Relieves Mitral Regurgitation

For high-risk surgical patients with severe symptomatic mitral regurgitation (MR), insertion of the Tendyne transcatheter mitral valve replacement (TMVR; Abbott) using a cardiac transapical approach resulted in excellent procedural success, relief of mitral regurgitation, and increases in cardiac hemodynamics and quality of life sustained at 1 year.

Further, patients with severe mitral annular calcification (MAC) showed improvements in hemodynamics, functional status, and quality of life after the procedure.

With 70 centers participating in the Tendyne SUMMIT trial, the first 100 trial roll-in patients accrued from the first one or two patients from each site without previous Tendyne TMVR experience.

"For this new procedure, with new operators, there was no intraprocedural mortality, and procedural survival was 100%," co-primary investigator Jason Rogers, MD, of the University of California Davis Medical Center, Sacramento, told attendees at a Late-Breaking Clinical Science session here at the Transcatheter Cardiovascular Therapeutics 2023 congress.

"The survival was 74% at 12 months. The valve was very effective at eliminating much regurgitation, and 96.5% of patients had either zero or 1+ at a year, and 97% at 30 days had no mitral regurgitation," he reported. As follow-up was during the COVID-19 pandemic, several of the deaths were attributed to COVID.

Device and Trial Designs

The Tendyne TMVR is placed through the cardiac apex. It has an outer frame contoured to comport with the shape of the native mitral valve. Inside is a circular, self-expanding, tri-leaflet bioprosthetic valve.

A unique aspect of the design is a tether attached to the outflow side of the valve to allow positioning and control of the valve. At the end of the tether is an apical pad that is placed over the apical access site to control bleeding. The device is currently limited to investigational use in the United States.

The trial enrolled patients with grade III/IV MR or severe MAC if valve anatomy was deemed amenable to transcatheter repair or met MitraClip indications and if these treatments were considered more appropriate than surgery.

Rogers reported on the first 100 roll-in (early experimental) patients who received Tendyne TMVR. There was a separate severe MAC cohort receiving Tendyne implantation (N = 103). A further 1:1 randomized study of 382 patients compared Tendyne investigational treatment with a MitraClip control group.

At baseline, the 100 roll-in patients had an average age of 75 years, 54% were men, 46% had a frailty score of 2 or greater, and 41% had been hospitalized in the prior 12 months for heart failure. Left ventricular ejection fraction (LVEF) was 48.6% ± 10.3%.

Improved Cardiac Function

Procedural survival was 100%, technical success 94%, and valve implantation occurred in 97%. Of the first 100 patients, 26 had died by 1 year, and two withdrew consent, leaving 72 for evaluation.

Immediate post-procedure survival was 98%, 87.9% at 3 months, 83.7% at 6 months, and 74.3% at 1 year. MR severity decreased from 29% 3+ and 69% 4+ at baseline to 96.5% 0/1+ and 3.5% 2+ at 1 year.

Cumulative adverse outcomes at 1 year were 27% all-cause mortality, 21.6% cardiovascular mortality, 5.4% all-cause stroke, 2.3% myocardial infarction (MI), 2.2% post-operative mitral reintervention, no major but 2.3% minor device thrombosis, and 32.4% major bleeding.

Most adverse events occurred peri-procedurally or within the first month, representing, "I think, a new procedure with new operators and a high real risk population," Rogers said.

Echocardiography at 1 year compared with baseline showed significant changes with decreases in left ventricular end diastolic volume (LVEDV), increases in cardiac output (CO) and forward stroke volume, and no change in mitral valve gradient or left ventricular outflow tract (LVOT) gradient. New York Heart Association (NYHA) classification decreased from 69% class III/IV at baseline to 20% at 1 year, at which point 80% of patients were in class I/II.

"There was a consistent and steady improvement in KCCQ [Kansas City Cardiomyopathy Questionnaire] score, as expected, as patients recovered from this invasive procedure," Rogers said. The 1-year score was 68.7, representing fair to good quality of life.

Outcomes With Severe MAC

After screening for MR 3+ or greater, severe mitral stenosis, or moderate MR plus mitral stenosis, 103 eligible patients were treated with the Tendyne device. The median MAC volume of the cohort was 4000 mm³, with a maximum of 38,000 mm³.

Patients averaged 78 years old, 44.7% male, 55.3% had a frailty score of 2 or greater, 73.8% were in NYHA class III or greater, and 29.1% had been hospitalized within the prior 12 months for heart failure. Grade III or IV MR severity was present in 89%, with MR being primary in 90.3% of patients, and 10.7% had severe mitral stenosis.

Tendyne procedure survival was 98.1%, technical success was 94.2%, and valves were implanted in all patients. Emergency surgery or other intervention was required in 5.8%.

As co-presenter of the SUMMIT results, Vinod Thourani, MD, of the Piedmont Heart Institute in Atlanta, Georgia, said at 30 days there was 6.8% all-cause mortality, all of it cardiovascular. There was one disabling stroke, one MI, no device thrombosis, and 21.4% major bleeding.

"At 1 month, there was less than grade 1 mitral regurgitation in all patients," he reported, vs 89% grade 3+/4+ at baseline. "At 1 month, it was an improvement in the NYHA classification to almost 70% in class I or II, which was improved from baseline of 26% in NYHA class I or II."

Hemodynamic parameters all showed improvement, with a reduction in LVEF, LVEDV, and mitral valve gradient and increases in CO and forward stroke volume. There was no significant increase in LVOT gradient.

There was a small improvement in the KCCQ quality of life score from a baseline score of 49.2 to 52.3 at 30 days. "We're expecting the KCCQ overall score to improve on 1 year follow up since the patients [are] still recovering from their thoracotomy incision," Thourani predicted.

He said the primary endpoint will be evaluated at 1 year post procedure.

No Good Option

Designated discussant Joanna Chikwe, MD, chair of cardiac surgery at Cedars-Sinai Medical Center in Los Angeles, first thanked the presenters for their trial, saying, "What an absolute pleasure to be a mitral surgeon at a meeting where you're presenting a solution for something that we find incredibly challenging. There's no good transcatheter option for MAC. There's no great surgical option for MAC."

She noted the small size of the MAC cohort and asked what drove failure in patient screening, starting with 474 patients, identifying 120 who would be eligible, and enrolling 103 in the MAC cohort. The presenters identified neo-LVOT, the residual LVOT created after implanting the mitral valve prosthesis. Screening also eliminated patients with a too large or too small annulus.

Thourani said in Europe, surgeons have used anterior leaflet splitting before Tendyne, which may help to expand the population of eligible patients, but no leaflet modification was allowed in the SUMMIT trial.

Chikwe then pointed to the six deaths in the MAC arm and 11 deaths in the roll-in arm and asked about the mechanism of these deaths. "Was it [that] the 22% major bleeding is transapical? Really the Achilles heel of this procedure? Is this something that could become a transcatheter device?"

"We call it a transcatheter procedure, but it's very much a surgical procedure," Rogers answered. "And, you know, despite having great experienced sites...many surgeons don't deal with the apex very much." Furthermore, catheter insertion can lead to bleeding complications.

He noted that the roll-in patients were the first one or two cases at each site, and there have been improvements with site experience. The apical pads assist in hemostasis. He said the current design of the Tendyne catheter-delivered valve does not allow it to be adapted to a transfemoral transseptal approach.

Rogers is a consultant to and co-national principal investigator of the SUMMIT Pivotal Trial for Abbott. He is a consultant to Boston Scientific and a consultant/equity holder in Laminar. Thourani has received grant/research support from Abbott Vascular, Artivion, AtriCure, Boston Scientific, Croivalve, Edwards Lifesciences, JenaValve, Medtronic, and Trisol; consultant fees/honoraria from Abbott Vascular, Artivion, AtriCure, Boston Scientific, Croivalve, and Edwards Lifesciences; and has an executive role/ownership interest in DASI Simulations. Chikwe reports no relevant financial relationships. The SUMMIT trial was sponsored by Abbott.

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