Studies Investigate Transfemoral Mitral Valve Replacement

Massachusetts General Hospital is investigating the safety and efficacy of two novel transcatheter mitral valve replacement (TMVR) technologies as part of two national multicenter clinical trials.

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In the ENCIRCLE Trial, Mass General researchers became the first group in New England to perform the first-of-its-kind transcatheter valve replacement within a native mitral valve utilizing the Edwards SAPIEN M3 System. The same team also performed the first transfemoral mitral valve replacement in the U.S. using the Medtronic Intrepid^TM Transcatheter Mitral Valve Replacement System within the APOLLO Trial. Both procedures treat severe mitral regurgitation (MR), the most common form of valvular heart disease in adults.

"These are older patients who are often high-risk for open-heart surgery and face prolonged recovery periods. Transcatheter therapies will open up alternative treatment strategies that will have a big impact on patient lives," says Sammy Elmariah, MD, MPH, an interventional cardiologist at the Corrigan Minehan Heart Center and director of the Interventional Cardiology Research Program at Mass General. "Novel transcatheter mitral valve replacement technologies have been in clinical testing for several years, and Mass General has played a prominent role to date. This new technology represents a major advance by allowing us to implant these valves through an artery in the leg instead of through the chest, leading to an easier, more rapid recovery."

Evolution of Minimally Invasive Surgery to Treat Valvular Heart Disease

Historically, surgical treatment for severe valvular heart disease was limited to open replacement procedures. But with the rapid emergence of transcatheter aortic valve replacement (TAVR), patients now have access to an effective minimally invasive option. "We initially started off with the aortic valve and TAVR because the anatomy of aortic valves is much simpler," says Dr. Elmariah. "Today, TAVR is a routine procedure that has completely changed the standard of care for valvular heart disease."

But mitral valve replacement presents a significant challenge due to the mitral valve's dynamic and complex anatomy. Unlike the aortic valve, the mitral valve does not have a rigid, calcified annulus to hold the replacement valve in position.

"We can perform TAVR without disrupting any anatomic structures around the aortic valve," explains Dr. Elmariah. "But the mitral valve is in the middle of the heart. You are not only dealing with the valve itself, but you are interacting with the left ventricular tissues, potentially an artery that courses around the mitral valve and the aortic valve as well. It has taken a lot of engineering to develop technologies that fix themselves to the tissues of the mitral valve and the mitral valve annulus."

Severe mitral valve regurgitation's current standard of care remains open cardiac surgery, although clinicians can treat a subset of patients using transcatheter mitral valve repair (TMVr) devices like Mitraclip^TM. Mitraclip allows interventional cardiologists to perform edge-to-edge repairs on the mitral valve to lessen the degree of regurgitation. "While these procedures have been quite effective, there are many anatomies that these devices do not work for or where we cannot achieve expected results," says Dr. Elmariah.

The development of two transapical TMVR devices increased treatment options. During these procedures, physicians inserted a finger-sized catheter into the tip of the heart, which then required suturing. But injuring the heart in this way puts patients at increased risk of complications, has a recovery period similar to open-heart surgery and can be detrimental to patients with weaker hearts.

"Based on early results, the quality of life of these patients does not return to normal for several months after the procedure," says Dr. Elmariah. "That is why the introduction of these newer transfemoral technologies is something we have been waiting years for. They have the potential to completely revolutionize how we treat mitral valve disease."

About the ENCIRCLE Trial

The ENCIRCLE Trial is a prospective, single-arm clinical trial for symptomatic patients who would be high-risk surgical candidates and do not have anatomy suited for the current FDA-approved edge-to-edge repair device. To overcome the challenges inherent in mitral valve anatomy, Mass General's heart team performs a two-stage valve deployment system:

1. They deploy a nickel-titanium (nitinol) dock that provides a place to anchor the SAPIEN M3 mitral valve. The dock is like a large coil that slowly deploys so it encircles the sub-valvular apparatus of the mitral valve
2. The dock creates a rigid landing zone for the balloon-expandable heart valve

The ENCIRCLE Trial plans to enroll 500 patients. Mass General was among the first sites in the U.S. to perform this procedure and has since completed three Edwards mitral valve replacements. Recruitment is ongoing for new patients with both primary and degenerative MR.

"We plan to assess what impact this device and the alleviation of mitral regurgitation has in regard to survival and readmissions for heart failure and other medical cardiac complications," says Dr. Elmariah. "Once investigators enroll the full cohort, the hope is that ENCIRCLE will be used for FDA approval."

About the APOLLO Intrepid TMVR Clinical Trial

The APOLLO Intrepid TMVR clinical trial features a self-expandable valve that initially utilized a transapical approach. The device protrudes to conform and engage with the surrounding annulus of the mitral valve, so it stays firmly in position.

The APOLLO Trial plans to enroll approximately 1,350 participants across dozens of centers in the U.S. Mass General's team was the first in New England to perform the procedure via transapical access and the first in the U.S. to implant the Medtronic valve using a transfemoral approach.

"Despite great results with the transapical approach, the recovery can be challenging, and some patients with other forms of heart disease or heart failure may not do well with a catheter put into the tip of their heart," explains Dr. Elmariah.

While investigators anticipate fewer complications and easier recoveries with transfemoral access, the device requires a surgical cut down of the femoral vein due to the catheter's size. "Because of that, they have taken the added step of requiring a surgeon to perform a cut down for us to access the vein. With the SAPIEN M3 mitral valve system, we put a needle straight into the vein and utilize standard percutaneous catheterization approaches," Dr. Elmariah adds. "Both devices have technical nuances that may favor one patient or another, most likely because of individual anatomy."

A Multidisciplinary Approach Leads to Success

Mass General's heart team for the ENCIRCLE and APOLLO TMVR clinical trials includes:

• Cardiac surgery: Nathaniel Langer, MD, MSc, and Serguei Melnitchouk, MD, MPH
• Interventional cardiology: Ignacio Inglessis-Azuaje, MD (site principal investigator for APOLLO), and Dr. Elmariah (site principal investigator for ENCIRCLE)
• Interventional echocardiography: Jonathan Passeri, MD, and Jacob Dal-Bianco, MD
• Cardiac anesthesia: Jerome Crowley, MD, MPH, Adam Dalia, MD, MBA, and Michael Fitzsimons, MD

"These are multidisciplinary endeavors that require an exceptionally skilled team to perform them successfully," notes Dr. Elmariah. "Every team member is critical to the success of these procedures, especially something as novel as this."

"At Mass General, we have a long history of working together in the transcatheter valve space, along with robust, well-developed multidisciplinary teams that contribute to our successful outcomes."

He predicts the transcatheter mitral valve space will experience a rapid evolution like the one seen in aortic valve technologies. "The ultimate hope is that we can treat all patients who have mitral valve disease with transcatheter means, and that will be a tremendous advance for the field and our patients."

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