Two Transcatheter Mitral Valves: Promising Early Experience

Neil Osterweil

November 28, 2017

DENVER, CO — Two cardiac valve prostheses, similar in capability, offer the prospect of significant relief of mitral regurgitation (MR) via transcatheter mitral-valve replacement (TMVR) for patients who are ineligible for mitral-valve surgery.

In the Intrepid (Medtronic) pilot trial reported at TCT 2017, ECG studies confirmed that all patients who received the Intrepid TMVR device had either mild or no MR on follow-up, compared with 96% with severe MR at baseline[1].

More than three-fourths of patients were in NYHA class 1 or 2 heart failure at the last follow-up, whereas at baseline 86% of the cohort had been in class 3 or 4, according to Dr Paul Sorajja (Minneapolis Heart Institute, MN), who reported the study here at TCT 2017 to coincide with its publication in the Journal of the American College of Cardiology, on which he is senior author.

Also, a global feasibility trial of a different TVMR device, the Tendyne TMVR (Tendyne Holdings), showed that the retrievable and repositionable device was associated with "encouraging" mid-term clinical and ECG results, with no MR in 95% of patients treated, Dr David WM Muller (St Vincent's Hospital, Sydney, Australia) reported at the conference.

TMVR Could Join TAVR

Although both devices are in the early clinical-trial stage and neither has yet gone head-to-head against surgical mitral-valve replacement in a randomized trial, the early results suggest that TMVR may soon join transcatheter aortic-valve replacement (TAVR) as a less invasive alternative to the surgical option, Sorajja told | Medscape Cardiology.

The pivotal trials comparing TMVR with surgery will be enrolling patients with Society of Thoracic Surgeons (STS) mitral repair/replacement scores of 3 or greater, ranging from intermediate to high risk, he noted.

"There are going to be a lot of intermediate-risk patients in those trials. So for the patients who could have surgical mitral-valve replacement, I'm hoping that the trial will show noninferiority for TMVR and that the impact on MR reductions and [the effect on symptoms] will be comparable," Sorajja said.

In a briefing prior to presentation of both studies in a late-breaking clinical-trials session, Sorajja said that after "the very first case we did, a surgeon looked at me and said 'I can't imagine doing a valve any other way.' "

Intrepid, Featuring Bovine Tissue

The Intrepid prosthesis is a self-expanding nitinol valve that comes in a 43-, 46-, or 50-mm diameter circular outer fixation frame that houses a 27-mm trileaflet bovine-tissue valve. The device is implanted via a transapical delivery system using 35 Fr access. The device is designed to wedge in the subannular mitral space.

The study included 50 consecutive patients who received the device from May 2015 through July 2017 at 14 participating sites in the US, Europe, and Australia.

The patients were 18 or older with symptomatic, severe MR, no or minimal mitral calcification, and an LVEF of at least 20%. All patients were judged by local heart teams to be at high or extreme risk for complications or death from open MV surgery.

The median procedure duration was 100 minutes, and the median device deployment time was 14 minutes. The procedure was aborted in one patient and was successful in 48 of the remaining 49. There were no device malfunctions or failures, and no need for converting to open MV replacement.

Clinical Outcomes in the Intrepid Pilot Study

End point 0–30 d, n=50 (%) >30 d, n=41 (%)
Death 14.0 9.8
Disabling stroke 0.0 0.0
Nondisabling stroke 4.0 2.4
MI  0.0 0.0
Acute renal impairment, stage 3 10.0 0.0
Reoperation for bleeding 10.0 0.0
New-onset atrial fibrillation 14.0 4.9
Device embolization, hemolysis, or thrombosis  0.0 0.0
Rehospitalization for heart failure 8.0 19.5

MR regurgitation was severe in 95.9% of patients at baseline and moderate in the remaining 4.1%. At both 30 days and at last follow-up, 73.8% of patients had no MR, and 26.2% had only mild MR.

At baseline, 16% of patients were in NYHA class 4 heart failure, 70% were in class 3, and 14% were in class 2. At last follow-up (median 173 days), there were no patients in class 4, 20.9% were in class 3, 44.2% in class 2, and 34.9% were in class 1.

Of the seven patients who died within 30 days of the procedure, three died from apical bleeding, three from CHF, and one from malposition. There were no deaths after 180 days. The 1-year survival rate was 76.5%.

Tendyne: Porcine Pericardial Tissue

The Tendyne transcatheter mitral valve consists of a trileaflet porcine pericardial valve in a self-expanding nitinol double frame.

Unlike the Intrepid device, the Tendyne device has a tether that is attached to an endocardial pad that lies outside the apical puncture site and is thought to help control bleeding from the apex. The fixation device allows the valve to be fully retrievable and repositionable until the tether is cut.

In a global feasibility study, Muller and colleagues in hospitals in Australia, Norway, and the US enrolled 30 adult patients with severe MR of primary or secondary origin and NYHA functional class 2 or 3 or ambulatory class 4 heart failure who were deemed to be poor candidates for cardiac surgery by a heart team that included a cardiologist and cardiac surgeon.

Of the 30 patients enrolled, implantation was not successful in two, five patients died (four from cardiac and one from noncardiac causes) within the first year, and one withdrew consent, leaving 22 patients for the analysis of 1-year outcomes.

There were 25 men and five women enrolled. Fourteen patients (46.7%) had NYHA functional class 2, and 16 (53.3%) had class 3. The mean STS score was 7.3.

At 1 year, 83% of the original 30 patients were still alive. There were no cases of stroke or transient ischemic attacks. Three patients were rehospitalized for heart failure, but none required mitral-valve surgery.

One patient had a malpositioned device with a small paravalvular leak with hemolysis, and a second patient had a leaflet thrombosis that was treated successfully with therapeutic anticoagulation.

MR severity at baseline was grade 4 in 89.5% of patients and grade 3 in 10.5%. At 1 month, 5.3% of patients had grade 1 MR, and 94.7% had no MR. At 1 year, the 5.3% had grade 2 MR, but 94.7% remained MR free.

The mean LVEF fell from 46.7% at baseline to 42.0% at 3 months and 38.4% at 1 year, but there was no significant difference between the 1-month and 1-year time points.

NYHA class improved after TMVR, with 25% of patients in class 1 at 1 month (vs none at baseline) and 40% in class 1 at 1 year. The proportion of patients in NYHA class 2 also improved over time, from 46.7% at baseline, to 50% at 1 month, to 55% at 1 year. Only one patient was in NYHA class 3 at 1 year.

Changes in quality of life (QoL) from baseline to 1 year were measured by responses to the Kansas City Cardiomyopathy Questionnaire (KCCQ). For 22 patients for whom complete data were available, QoL improved significantly from baseline to 1 month, and from 1 month to 1 year (P<0.001 for each comparison).

Mitral Valves "Extraordinarily Complicated"

In a briefing prior to presentation of both studies in a late-breaking clinical trials session, / Medscape Cardiology asked Muller if he had an explanation for the decline in LVEF. He said that those data came from 19 patients evaluated at all three time points and implied that the population is too small to detect a meaningful effect.

Dr Gary S Mintz (Cardiovascular Research Foundation, New York, NY), who comoderated the briefing, told | Medscape Cardiology that TMVR is a much more challenging than TAVR, but the technology is advancing quickly.

"Mitral valves are extraordinarily complicated anatomic structures. The aortic valve is dumb; it's an annulus," he said. "Aortic stenosis is essentially one pathway to the disease process, as opposed to mitral-valve disease, which has multiple underlying etiologies," he said.

Now that TAVR has come into its own, "resources are being poured into the mitral-valve space," he added, and there will likely be an exponential growth in both less invasive mitral-valve procedures and device development, he said.

The Intrepid Pilot Study was funded by Medtronic. Sorajja discloses receiving grant support from Abbott Vascular, Boston Scientific, Edwards Lifesciences, and Medtronic; and fees or honoraria from Abbott Vascular, Boston Scientific, Edwards Lifesciences, Integer, and Medtronic. The Tendyne Global Feasibility Study was funded by Tendyne Holdings, a subsidiary of Abbott. Muller disclosed grant support from Medtronic and Tendyne and consulting fees or honoraria from Abbott, Medtronic, Boston Scientific, 4Tech, and Cephea. Mintz disclosed research support and fees from Boston Scientific and has previously reported receiving grants from St Jude, grants and personal fees from Boston Scientific and Volcano, and personal fees from Acis. 

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