Bicuspid Aortic Valves Present Challenges for TAVR
It remains to be determined if TAVR is optimal in patients with severe aortic stenosis and bicuspid aortic valves.
Most clinical research for transcatheter aortic valve replacement in patients with severe aortic stenosis has been performed in patients with tricuspid aortic valves. However, many patients who require AVR, particularly younger individuals, have bicuspid aortic valves, and data on the appropriateness of TAVR for them are scarce. Fortunately, more research is being conducted in this area and registries have been created.
Until more definitive findings are published, however, the suitability of TAVR for bicuspid aortic valves must be determined on a case-by-case basis. Cardiology Today’s Intervention spoke with Samir R. Kapadia, MD, Rajendra Makkar, MD, and Michael J. Reardon, MD, to delineate some of the issues that must be considered.
Is TAVR appropriate for patients with bicuspid aortic valves?
Samir R. Kapadia, MD
There are several different types of bicuspid aortic valves. They come in various forms anatomically. In the surgical literature, almost 40% of patients, even those aged older than 70 years, undergoing AVR have a bicuspid valve when examined by pathologists.
TAVR is a good choice for selected patients with bicuspid aortic valves, but not all bicuspid aortic valves. When it is a good choice is something that we are still learning. There are cases where the raphe is not complete and does not go from the base to the tip of the leaflet, and is not heavily calcified. If the raphe allows for more or less circular deployment of the valve, then it is a good option for a TAVR valve. However, if the raphe and commissures are calcified and cannot become circular with valve deployment, then there would likely be paravalvular leak around the artificial valve if TAVR was attempted.
A major question is how can we predict which orifice will conform to the circular TAVR valve. A second question is how do we size the valve appropriately. We are still learning this. Some studies suggest you measure in the usual manner at the annular level, while others suggest you measure higher, where the measurement could be smaller. We also need more understanding of whether self-expanding valves (CoreValve family of products, Medtronic) or balloon-expandable valves (Sapien family of products, Edwards Lifesciences) are better for certain types of anatomy. We have not yet been able to nail down those questions completely.
Fortunately, there is a TAVR for bicuspid valves registry with CT scan data and prospective planning for both Edwards and Medtronic valves. We are trying to collect scientifically analyzable data for both types of TAVR valves to help determine which valves work best in which anatomy.
Another challenge is that many patients with bicuspid aortic valves are young. They may live long enough to need a second valve after the first one fails. Durability is very important in these patients. Some data suggest that if the valve is not circular, leaflet thrombosis is somewhat higher. In other words, valve durability may be less if we cannot deploy the TAVR valve in a very circular fashion. We are also beginning to understand that where we place the valve — how deep or how high — may be very important.
We also have to keep in mind that surgical AVR in patients with bicuspid aortic valves who are young and have no risk factors has a mortality rate of much less than 1%. So we also have to ask what is the unmet need. Of course, people do not want to have open surgery, but if the risk is not significant, it may be difficult to recommend a newer therapy over another one which has proven to be a great option.
Also, 10% to 20% of patients with bicuspid aortic valves also have large aortas and need aortic replacement. This is an indication for surgery.
In the big picture, bicuspid is a very exciting field because it includes a very large number of patients with aortic stenosis. If we are going to pursue TAVR in these patients, we need to identify who has well-suited anatomy and who does not need other surgical procedures. If we can answer all these questions, TAVR for bicuspid aortic valves may become an option for low-risk patients. We know it is an excellent option for appropriate high-risk patients, but for low-risk patients, we need to learn more.
Rajendra Makkar, MD
Bicuspid aortic valve stenosis is frequent, noted in up to 2% to 6% of patients presenting with aortic stenosis. Bicuspid aortic stenosis is even more common in younger patients. As TAVR extends into the younger population, there is a need to find a safe, effective and durable solution for bicuspid aortic valve stenosis.
In carefully selected high-risk patients with bicuspid aortic stenosis, TAVR is a reasonable treatment option. In a study that we performed at Cedars-Sinai, the outcomes of TAVR with the current-generation transcatheter valves in bicuspid aortic stenosis were similar to tricuspid aortic stenosis.
One of the biggest challenges of TAVR in bicuspid aortic stenosis is the presence of excessive calcium on the aortic valve, especially a heavily calcified raphe.
Many patients with bicuspid aortic stenosis have concomitant aortopathy. Thus, it is important to evaluate for coexisting aortopathy, and not just the aortic valve, while evaluating a patient with bicuspid aortic stenosis for TAVR.
To make a definitive assessment about the role of TAVR in young patients with bicuspid aortic stenosis, we need a randomized controlled trial where TAVR is compared with surgery.
Michael J. Reardon, MD
Bicuspid aortic valves were an exclusion factor in all the U.S. TAVR IDE trials until the PARTNER III trial, which included a bicuspid aortic valve arm and is not yet available. Bicuspid valves, however, come in several varieties. The most common classification system is the Sievers system, which classifies according to the number of raphes. The most common type is Sievers 1. Within Sievers 1, the most common is with one raphe at the fusion of the left and right cusps. Even Sievers 1 type bicuspid valves can come in different flavors, with differing amount of fusion and calcification at the raphe.
TAVR clinicians and trial leaders recognized this and accepted some Sievers 1 bicuspid aortic valves with limited fusion of the raphe as a tricuspid valve that appeared functionally bicuspid. These valves are of course still congenital bicuspid aortic valves, but amenable to successful TAVR.
In clinical practice, functional bicuspid aortic valves are being treated with current-generation valves. Safety and efficacy with new-generation valves approach that seen in tricuspid valves.
Despite this success, questions remain in the treatment of bicuspid aortic valves with TAVR. Are all types of bicuspid aortic valves appropriate for TAVR? How best do we size and implant in bicuspid aortic valves? Is this the same or different than with tricuspid valves? Can we accurately predict arteriopathy and guide those patients to surgery?
I have no doubt that the boundaries for TAVR will continue to expand and indications for TAVR will be included in appropriate patients with bicuspid aortic valves. Our goal in the TAVR community should be to define the bicuspid aortic valve anatomy as it applies to TAVR sizing and implantation, and to assure continued excellent patient outcomes.
- Yoon SH, et al. J Am Coll Cardiol. 2017;doi:10.1016/j.jacc.2017.03.017.
- For more information:
- Samir R. Kapadia, MD, is section head of invasive and interventional cardiology and director of the Sones Cardiac Catheterization Laboratories and the Interventional Cardiology Fellowship Program at Cleveland Clinic. He can be reached at email@example.com.
- Rajendra Makkar, MD, is associate director of Smidt Heart Institute at Cedars-Sinai and a Cardiology Today’s Intervention Editorial Board Member. He can be reached at firstname.lastname@example.org.
- Michael J. Reardon, MD, is professor of cardiothoracic surgery and Allison Family Distinguished Chair of Cardiovascular Research at Houston Methodist DeBakey Heart and Vascular Center. He can be reached at email@example.com.
Disclosures: Kapadia reports no relevant financial disclosures. Makkar reports he has consulted for and received research grants from Abbott, Edwards Lifesciences and Medtronic. Reardon reports that his institution received consultant fees from Medtronic and that he serves as principal investigator for two trials sponsored by Boston Scientific and two trials sponsored by Medtronic.