TAVR Team Continuously Innovating to Treat Aortic Stenosis

Clinician-researchers in the Heart Valve Program at the Corrigan Minehan Heart Center at Massachusetts General Hospital are continuing their efforts to make transcatheter aortic valve replacement (TAVR) more effective and available to the largest possible number of patients with aortic stenosis.

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"Severe, symptomatic aortic stenosis is a life-threatening disease and has a life expectancy measured in single-digit years, just like metastatic cancer," says Nathaniel Langer, MD, MSc, a cardiac surgeon at the Corrigan Minehan Heart Center. "Once you have it, the clock is ticking, and we need to be able to treat it."

The team's latest advances build upon seminal research conducted at Mass General, the PARTNER trial, which originally established TAVR as a safe and effective minimally invasive option for patients with aortic stenosis who could not have surgery.

"Since the initial trial, Mass General has been involved in a series of other studies using a number of different devices that have shown equivalence and sometimes superiority of TAVR compared to surgical aortic valve replacement (AVR)," Dr. Langer says. "Those trials have entirely changed the surgical landscape—and really cardiology and cardiac surgery practices worldwide—in how we take care of patients with aortic stenosis."

Changing the Treatment Paradigm for a Common, Serious Disease

Aortic stenosis is a common condition marked by a narrowing of the aortic valve opening, which restricts blood flow out of the heart. It can result from a congenital heart defect such as a bicuspid aortic valve, or it can develop over time as a person ages and calcium accumulates on the valve. The disease can be latent for a long period of time but is progressive.

For decades, the gold standard treatment for aortic stenosis was open-heart surgical valve replacement. However, some people are not candidates for surgery due to additional health conditions that put them at extreme risk for poor outcomes. Others want to avoid surgery because of general surgical risks and the length of recovery.

TAVR was developed as an alternative to surgical intervention. In a TAVR procedure, a bioprosthetic valve is inserted using a catheter, usually through the femoral artery, and implanted in the native aortic valve. Ten years ago, Mass General researchers and others involved in the pivotal PARTNER trial found that TAVR reduced the rate of death from aortic stenosis in patients who were not candidates for surgical valve replacement.

Since that original trial, the Mass General team has contributed to additional studies of TAVR outcomes in varied cohorts of patients, not just those who with contraindications for surgery. Their findings in PARTNER II, CoreValve Evolut®, TAVR UNLOAD and ACURATE neo™ have expanded TAVR's indications and improved outcomes.

"As TAVR has rolled out into the cardiac surgery world, we and others have continued to conduct a sequence of trials using TAVR in ever-healthier patient populations. Early trials were performed in patients who were too sick to have surgery, then we studied patients at high risk, then moderate, then low," Dr. Langer says. "Over a year ago, TAVR was approved for patients in all risk categories, so it is now available to everyone. That has drastically altered how we think about who should have the procedure."

Tailoring TAVR Decisions

Now that TAVR is widely available, Mass General is focusing research efforts on evidence to help clinicians make tailored, individualized recommendations. Some of the factors they are considering include:

• Anatomy: The team is reviewing the effectiveness of TAVR in patients with bicuspid aortic valves, as original studies included only those with normal tricuspid valves. They are also examining results according to varying degrees of calcification and characteristics of the peripheral vessels
• Age: Younger patients (those in their 60s or 70s) may have been excluded in earlier clinical trials. Researchers and clinicians are now eager to learn how TAVR performs in active patients who are healthy enough for surgery but may prefer TAVR because of its minimally invasive nature. "In this population, TAVR will have to show that it performs at a very high level compared with the surgical approach," says Dr. Langer
• Comorbid conditions: Retrospective research is examining how TAVR performs in patients with additional heart conditions, such as coronary disease and heart failure
• Durability: The Mass General team also is following patients longitudinally to determine how durable the valves are. "Early trials were performed mostly in patients who were very sick and had life-limiting conditions, so real durability data were not available—only out to about five years," Dr. Langer explains. "Surgical valves are in the 15-year range, so we have a while before we understand whether TAVR is likely to last as long. This is important depending on the age of the patient and how long they may be expected to live"
• Device type: Because the Mass General team was involved in TAVR research from the beginning, they have access to and extensive experience with a wide range of valve types. "We can make very targeted decisions about which valve to use based on the characteristics for the patient, as opposed to only what we have on the shelf," Dr. Langer says
• Route: "The catheters and valves have gotten much smaller over generations of devices, but they are still relatively large, so you need a reasonably sized femoral artery and aorta to get the device to the heart," Dr. Langer says. His team has successfully used other routes when needed, including axillary, carotid, transaortic and transcaval access. "We have all of the tools at our disposal so the number of patients on whom we can't do a TAVR is exceedingly low."
• Failed prior valve surgery: In patients who have had a prior surgical aortic valve replacement that has failed, the Mass General team may consider a valve-in-valve TAVR procedure rather than repeat surgery. This involves placing a TAVR valve within a surgical valve, or a TAVR valve within a TAVR valve. Researchers are following these patients longitudinally to make sure this approach does not have unanticipated implications

"We are looking at ways to increase the granularity with which we can look at an individual patient and make a decision that is going to serve them best," Dr. Langer explains. "It would be very easy with TAVR to say that being out of the hospital in two days is better than being in the hospital for a week, but if that means that you need three procedures instead of one, that may not be the best decision. So having a team that really looks holistically at patients and does have the long-term view in mind makes sure that the cumulative benefit is maximized."

Lessons Learned From Thousands of Procedures

Mass General has developed an innovative, multidisciplinary team that makes balanced, informed decisions about valve treatment. The team includes:

• Structural interventional cardiologists who specialize in valves
• Cardiac surgeons
• Structural echocardiographers who are subspecialty-trained in imaging valves
• Nurse practitioners, physician assistants and research coordinators

"Our program has a huge collective experience," says Dr. Langer. "TAVR is available at more and more places, but the expertise sets us apart. Everyone in the room is subspecialty-trained and a leader in their field. That makes for a team where everyone trusts everyone, and everyone is on equal footing."

Forging Minimally Invasive Approaches for Other Heart Conditions

Building on their experience with TAVR, Mass General is now exploring ways to use similar minimally invasive approaches in other disease states.

"The aortic valve paradigm has ushered in a rapidly growing era for all transcatheter valve therapies, such as transcatheter mitral valve repair, mitral valve replacement, tricuspid valve problems and heart failure," Dr. Langer says. "We are applying the lessons we have learned to better treat all potential heart diseases without having to do open-heart surgery."

Learn more about the Heart Valve Program at Mass General

Refer a patient to the Corrigan Minehan Heart Center