First-in-Human Transcatheter Mitral Valve Replacement Cases Show Safety, Efficacy

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Transcatheter mitral valve replacement (TMVR) may soon be another tool in the interventional toolbox, as highlighted by a first-in-human series demonstrating safety and feasibility in 2 Canadian patients with severe mitral regurgitation (MR). The results are being published in the October 28, 2014, issue of the Journal of the American College of Cardiology.

“Catheter-based mitral valve implantation is technically feasible and may present another chapter in the evolution in the treatment of valvular heart disease,” Anson Cheung, MD, of St. Paul’s Hospital (Vancouver, Canada), and colleagues write.

For this case series, Dr. Cheung and colleagues implanted the device into 2 patients with end-stage ischemic cardiomyopathy and severe MR (table 1).

Both procedures were performed transapically in a hybrid OR with patients under general anesthesia with endotracheal intubation. Patients were hemodynamically stable with no need for cardiopulmonary bypass. Immediately after implantation, there were increases in systemic arterial pressure and stroke volume and a decrease in pulmonary pressure. No complications occurred during the procedures, and both patients were extubated in the OR.

Transesophageal echocardiogram  analysis at 4 days and 1 and 2 months postprocedure showed normal valve function with no evidence of thrombus formation, paravalvular leak, or left ventricular outflow tract obstruction in either patient. Although patient #1 was free of MR, he died on day 69 from refractory end-stage cardiac failure. Patient #2 had an uneventful recovery and demonstrated significant symptomatic and functional improvements.

A ‘Pioneering Effort’

In an accompanying editorial, Anelechi C. Anyanwu, MD, and David H. Adams, MD, both of Mount Sinai Medical Center (New York, NY), congratulate the researchers on their “pioneering effort, which serves as a proof-of-concept for transcatheter replacement in the noncalcified mitral valve.”

The routine application of this procedure “will be technically possible in the near future,” they write, adding that TMVR might possibly “revolutionize therapy for mitral valve disease, mirroring the course of TAVR.”

However, mitral valve disease is more complex compared with aortic disease treated with TAVR because there are numerous causes of MR and mitral stenosis, according to Drs. Anyanwu and Adams.

“Thus,” they write, “a single transcatheter prosthetic solution applicable to all etiologies is more challenging, and prostheses or techniques might need to vary depending on the etiology and pathoanatomy.”

The editorialists point out other differences between TMVR and TAVR:

• A younger patient population for TMVR vs TAVR, leading researchers and regulators to put more emphasis on long-term device durability
• Outcomes with surgery vs intervention are potentially more divergent with TAVR compared to TMVR, and finding the perfect “inoperable” patient may be harder with the latter
• A potentially higher risk to surrounding structures with TMVR vs TAVR
• Paravalvular leak is associated with greater mortality and morbidity in the mitral valve compared with the aortic

Given that mitral valve disease is not associated with high short-term mortality, the benefits of TMVR may not be as noticeable as those of TAVR and will be more evident in quality of life

Durability the Next Challenge

In a telephone interview with TCTMD, Timothy J. Gardner, MD, of Christiana Care Health System (Wilmington, DE), said that he agreed with the editorial on many points but described it as “somewhat too pessimistic or negative. I think this is a really exciting and important development.”

More patient experience will be necessary to take this procedure to the next level, he said, suggesting that a series of 50 or 100 patients would be useful to demonstrate safety and efficacy.

Then the focus can shift to durability, Dr. Gardner continued. “The experience with the early aortic catheter valves was not so good. It took a lot of refinements both in the technique of insertion and refinements to the prosthetic valve itself. So I think this will be a challenge that will go on for several years,” he said. “But they're off and running now, and I think a lot of people were skeptical that they would be able to develop a [mitral] valve that would work and they have.”

Sources:
1. Cheung A, Webb J, Verheye S, et al. Short-term results of transapical transcatheter mitral valve implantation for mitral regurgitation. J Am Coll Cardiol. 2014;64:1814-1819.

2. Anyanwu AC, Adams DH. Transcatheter mitral valve replacement: the next revolution [editorial]? J Am Coll Cardiol. 2014;64:1820-1824.

Related Stories:

• Studies Document Initial Steps Toward Percutaneous Mitral Valve Replacement
• Preclinical Data Show Safety, Efficacy of Transcatheter Mitral Valve
• Similar Long-term Benefits With Mitral Valve Repair, Replacement for Ischemic MR