NEW YORK – What if correcting secondary mitral regurgitation doesn’t improve patients’ lives or helps them live longer? What if results of the COAPT trial of the MitraClip (Abbott Vascular) repair for mitral regurgitation are negative or inconclusive? What if transcatheter mitral valve repair works too well?
The answers to these questions could determine the future landscape of transcatheter mitral valve replacement (TMVR) for mitral regurgitation (MR) and the prosthetics in various stages of clinical and preclinical investigation, Dr. Michael Mack of Baylor University said at the 2015 Mitral Valve Conclave, which was sponsored by the American Association for Thoracic Surgery.
Dr. Michael Mack
Dr. Mack reviewed the first four transcatheter mitral valve replacement devices approved for early feasibility studies in the United States, noting that “it has become a very crowded field very quickly,” especially when one considers that only between 20 and 50 TMVR procedures have been done worldwide up until now.
For the makers of the devices, it is becoming a potentially perilous field as well. Replacement, Dr. Mack said, does meet a “large clinical unmet need” in that it can completely correct mitral regurgitation better than valve repair.
“But what are the challenges for transcatheter mitral valve replacement and why isn’t this going to be the same as TAVR (transcatheter aortic valve replacement) all over again?” he said. “Unlike aortic stenosis, there is not a single cause of mitral regurgitation. In addition, it has never even been definitively proven that correcting MR helps prolong survival and improve quality of life.”
Another obstacle for TMVR is that delivery of the device into the mitral valve is more complex than doing so in the aortic valve. “The seating and the anchoring of the valve is more complex,” Dr. Mack said. “Based on the profile of the device, left ventricular outflow tract obstruction can be an issue, and perivalvular leak may carry more import here because mitral perivalvular leaks have the potential to cause hemololysis.”
He reviewed the four systems cleared for early feasibility studies.
CardiAQ (CardiAQ Valve Technologies), a porcine pericardial valve, has been implanted in eight patients worldwide and last month received Food and Drug Administration (FDA) approval for early feasibility study in 20 U.S. patients: 10 by a transfemoral approach and 10 by a transapical approach.
Tendyne Bioprosthetic Mitral Valve (Tendyne Holdings), a trileaflet porcine pericardium, also has been implanted in eight patients worldwide and was used for the first time in the United States last month by Dr. Wes Pederson and colleagues at the Minneapolis Heart Institute.
FORTIS (Edwards Lifesciences), a bovine pericardium valve, has been implanted in early feasibility trials in Europe and has been approved for an early feasibility trial of 15 patients in the United States.
Tiara (Neovasc), a D-shaped bovine pericardium valve, received FDA approval last year for the TIARA-I early feasibility trial in the United States (NCT02276547). The trial will enroll up to 30 patients worldwide.
At least five other TMVR devices are in preclinical studies, Dr. Mack said. These emerging devices face “threats and obstacles” as they move through the pipeline – a number of “what ifs,” Dr. Mack said.
“What if you can’t prove that correcting secondary mitral regurgitation makes a difference? What are the repercussions of the COAPT Trial (NCT01626079) of the MitraClip if it is positive and shows that correcting mitral regurgitation does make a difference? Does completely correcting mitral regurgitation then really make a difference? What if transcatheter mitral valve repair works too well?” (COAPT stands for Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation). “With the excellent safety profile of MitraClip, it may be hard to justify TMVR,” he said.
Dr. Mack noted that MitraClip for mitral valve repair has “a superb safety profile.” He added, “How do you choose what patients should be treated by a mitral valve replacement vs. a MitraClip by a transfemoral venous approach that enables them to go home the next day?”
The early feasibility trials of TMVR devices may point a way to answers.
Dr. Mack has received research grants from Edwards Lifesciences. He is a principal investigator in the ongoing COAPT Trial, which is sponsored by EVALVE with the collaboration of Abbott Vascular.