Implantation of an experimental transcatheter mitral valve in inoperable patients with severe functional mitral regurgitation (MR) is feasible and results in improvements in function and quality of life (QoL) that persist out to 6 months, according to a 3-case series published in the September 1, 2015, issue of the Journal of the American College of Cardiology.

Investigators led by Josep Rodés-Cabau, MD, of the Quebec Heart and Lung Institute (Quebec City, Canada), implanted the experimental Fortis transcatheter mitral valve (Edwards Lifesciences) in 3 patients with isolated severe (3+ or 4) functional MR. A multidisciplinary heart team had judged all to be at prohibitive risk for surgical replacement or repair.

The Fortis valve consists of a self-expanding nitinol frame, trileaflet bovine pericardial tissue, an atrial flange, and 2 opposing paddles that capture the native mitral leaflets and secure them to the frame.

All of the patients—2 men (67 and 81 years) and 1 woman (65 years)—had a history of CAD with prior CABG and symptomatic ischemic cardiomyopathy (LVEF ≤ 30%) with at least 1 heart failure admission within the previous 6 months.

The procedures were performed transapically under general anesthesia. IV heparin, adjusted to an activated clotting time greater than 250 seconds, was administered during the procedure, and aspirin (80 mg) was given beforehand and afterward. In addition, warfarin was started after the procedure and continued for at least 3 months; in those with baseline A-fib, warfarin was given indefinitely while aspirin was continued for at least 3 months.

Device Success in All 3 Patients

Procedural success—defined as implantation of a functioning valve within the mitral annulus without intraprocedural mortality or moderate/severe residual mitral regurgitation and/or mitral stenosis—was 100%, with no major complications. The mean transmitral gradient was 3 mm Hg, with none higher than 4 mm Hg. After the procedure, 1 patient experienced acute worsening of renal function and 1 required transfusion. Echocardiography before discharge showed no mitral regurgitation in 1 patient and trivial leak in 2. There were no increases in aortic outflow gradient.

At 3-month follow-up, echocardiography showed normal prosthesis function with only a trace leak in 1 patient. Transmitral gradients remained similar to postprocedural levels, while mean left ventricular outflow tract (LVOT) gradients ranged from 2 to 5 mm Hg. LVEF values were similar to baseline. No cases of valve thrombus or fracture were seen.

In addition, all patients showed improvements in NYHA functional class, 6-minute walk distance, activity status, and QoL.

At 30 days, the female patient was hospitalized due to GI bleeding, so she discontinued warfarin and aspirin and began taking clopidogrel. At 6 months, all 3 patients remained alive with no major complications and in NYHA class II or lower.

Valve Thrombosis Halts Trial

The appropriate antithrombotic therapy following implantation is unknown, the authors say. That fact was underscored when, in May 2015, Edwards temporarily halted a prospective Fortis trial due to evidence of valve thrombosis, according to a company press release.

The current report “highlights several aspects of the procedure that will apply to all future valve designs,” write Howard A. Cohen, MD, and Brian P. O’Neill, MD, of the Temple University Heart and Vascular Institute (Philadelphia, PA), in an accompanying editorial.

For example, CT will “continue to play a vital preplanning role in accurate sizing of the [mitral valve] annulus to strike a delicate balance between undersizing (and paravalvular leak) and oversizing (and LVOT obstruction),” they write. Three-D printing may help model the heart and allow insertion of differently sized ‘model valves’ before the actual procedure. Meanwhile, they add, TEE will remain “critical to success by confirming accurate transapical access to maintain coaxiality of the valve system and assessing, in real time, residual MR and gradients across the [mitral valve] and LVOT.” 

Possible Alternative Access

A drawback of the current technology is the large delivery sheaths that enter via the LV apex, Drs. Cohen and O’Neill observe. Because many nonsurgical candidates already have severe LV dysfunction, transseptal delivery systems have the potential to make the procedure safer. Moreover, the devices will likely become “smaller and more user friendly, thus facilitating their delivery,” they add.

In an email with TCTMD, Dr. Rodés-Cabau said that a transfemoral approach, if feasible, would be a major advantage because it is less invasive. “However, transapical replacement is probably a more direct and easier procedure,” he noted. “It remains to be proven if transfemoral replacement can be performed with similar success to transapical replacement, but if so, the transfemoral approach will take the lead.”

Meanwhile, it is “reasonable at the outset” to consider transcatheter replacement only for patients deemed to be at high risk, the editorialists say, because mitral valve surgery has set a high bar.

Ted Feldman, MD, of NorthShore University HealthSystem (Evanston, Illinois), agreed that “no options” patients should be the main target of this novel treatment. He added that while it is difficult to learn much from 3 cases, a clear lesson is that the success of the procedure rests on the combined expertise of a multidisciplinary team.

Drs. Feldman and Rodés-Cabau agreed that, compared with TAVR, percutaneous mitral valve replacement involves specific challenges including potential interference with and obstruction of the LVOT, which can be life-threatening. Patient screening with extensive preprocedural imaging is especially important to prevent the complication, Dr. Rodés-Cabau said.

In July 2015, Edwards announced that it has agreed to acquire CardiAQ Valve Technologies, maker of another transcatheter mitral device. In a press release, Edwards chairman and CEO Michael A. Mussallem said, “We believe the experiences and technologies of Fortis and CardiAQ are complementary and that this combination will enable important advancements for patients.” The CardiAQ device is a self-anchoring system that can be delivered either transapically or transfemorally.

Looking forward, Dr. Rodés-Cabau said he considered transcatheter replacement as complementary to MitraClip (Abbott Vascular) repair. “Transcatheter replacement may be a very good option for patients with suboptimal anatomy for MitraClip,” he noted. “In addition, if the goal is no or trivial MR, then replacement seems superior. But the patient’s operative risk should also be considered, as MitraClip repair is currently a less invasive procedure. Of course, long-term follow-up and evaluation of the durability of each strategy will be very important.”

Sources: 
1. Altisent OA-J, Dumont E, Dagenais F, et al. Initial experience of transcatheter mitral valve replacement with a novel transcatheter mitral valve: procedural and 6-month follow-up results. J Am Coll Cardiol. 2015;66:1011-1019.
2. Cohen HA, O’Neill BP. TMVR: continuing the paradigm shift in valvular heart disease therapy. Hype or hope [editorial]? J Am Coll Cardiol. 2015;66:1020-1022.

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