Choice between self-expanding, balloon-expandable TAVR valve … – Healio

April 26, 2023

6 min read

Source: Healio Interviews.

Disclosures: Stoler reports proctoring cases and serving on the advisory board for all TAVR valve companies.

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During the past decade, the options for practitioners of transcatheter aortic valve replacement have expanded on a regular basis.

This wave of commercially available transcatheter valves has provided clinicians with more tools in their armamentarium, allowing them to individualize the treatment of aortic stenosis to the specific patient.

Robert C. Stoler, MD

All of these options have been great for us and for our patients, Robert C. Stoler, MD,director of the cardiac catheterization lab and co-chief of cardiology at Baylor Scott & White Heart and Vascular Hospital, told Healio. Additionally, there are new valves that we are testing in clinical trials that will continue to expand our options.

Although having more choices is unquestionably a win-win for clinician and patient alike, it does lead to more questions; and one question that clinicians must ask themselves is whether a balloon-expandable or self-expanding TAVR valve is preferable for a given patient.

To help answer this question, Healio spoke with Stoler, who shared his knowledge on both TAVR valves, including the distinctions between the two, and the insights he has gleaned in his years working with the balloon-expandable and self-expanding iterations.

Healio: To start, can you describe the differences in mechanism of action between the self-expanding and balloon-expandable TAVR valves?

Stoler: The way you explain and describe the valves speaks to their mechanism exactly. Both are made of biological tissue: The balloon-expandable valve is bovine, and the most commonly used self-expanding valve, Evolut (Medtronic), is porcine. Both valves are mounted inside of a metallic frame.

Balloon-expandable vs. self-expanding describes how the valves open up once they are placed inside the body. For a balloon-expandable valve, the stent frame has leaflets inside it, and the valve is tightly crimped onto a balloon. The balloon is inserted into the femoral artery and expanded in the patients native aortic valve. The valve is then imbedded inside the native valve, which becomes the base for the implant.

In a self-expanding valve, the valve is made of nitinol, so when it gets to the temperature of blood after release, it expands on its own, beyond whatever its original size is.

Additionally, there are times when each of the valves needs to be re-ballooned, as a self-expanding valve may require a ballooning to expand it fully, while a balloon-expandable valve may require a second ballooning to accomplish the same.

Healio: What are the advantages and disadvantages for the balloon-expandable and self-expanding valves?

Stoler: In about 70% of patients, either valve would be effective. However, there are distinct advantages and disadvantages to each. Balloon expandable is probably easier to implant, and tends to be shorter, have a slightly lower pacemaker rate and be less difficult to get through the coronary arteries; so if a patient needs another heart catheterization after the TAVR is implanted, the balloon-expandable valve is easier to get back into the coronaries with.

But the downside for patients who have heavy calcium in certain areas of the heart is balloon-expandable valves are associated with a slightly higher risk of rupturing the heart. The balloon-expandable valve also tends to have a slightly smaller valve for each patient size than a self-expanding valve.

The issues with the self-expanding valve involve a slightly higher pacemaker rate and an increased difficulty in getting back into the coronaries after the valve is implanted. It is also a slightly more difficult technical implant.

Healio: Are the disadvantages a limitation of the mechanism of action? If so, might future iterations be redesigned to mitigate or negate these issues?

Stoler: Yes, the disadvantages are a consequence of the mechanism of action. For example, a self-expanding valve is taller than a balloon-expandable valve, and because of that, the metal is going to go across the coronaries, whereas with a shorter balloon-expandable valve, the metal will stay below the coronaries, making them easier to re-cannulate. Fortunately, there are ongoing technological advances being made in every one of the TAVR valves to make them easier to cannulate the coronaries through and less likely to result in the patient needing a pacemaker.

Healio: Earlier you mentioned that 70% of patients can receive either valve. For those remaining 30%, are there any patients in whom either the self-expanding or balloon-expandable valves would be preferred?

Stoler: Some physicians believe that patients who have very small aortic valve sizes will benefit from the self-expanding valve because a small annulus might only be large enough to receive, for example, a 23-mm balloon expandable valve compared with a 26- or 29-mm self-expanding valve. So for a small valve, a small annulus, a self-expanding valve may be preferred. Furthermore, in many patients who have a worn out previously surgically placed bioprosthetic valve, we can get a larger self-expanding valve in, and because of that, it may be the valve of choice.

On the other hand, for patients with extensive coronary disease, where access to the coronaries after the TAVR implant is of paramount importance, a balloon-expandable valve may be desirable because it makes re-cannulating the coronaries easier. Also, in patients with conduction system disease, a balloon-expandable valve, which has a smaller incidence of needing a pacemaker, might be a more desirable valve.

It is important to note that every patient who receives a TAVR valve gets a 3D CT scan, which has dedicated software to measure different parts of the heart. Those measurements and the distribution of calcium are factors that go into helping us decide which valve, if one or the other, may be a better fit.

Healio: Which transcatheter valve is more commonly used in practice today and why?

Stoler: Currently, the most commonly used valve is balloon expandable. I am not sure the exact figure, but I believe the balloon-expandable valve has two-thirds to three-quarters of the market share. There are two reasons for this. One is that it was the first to hit the market. While both valves have excellent outcomes data, the PARTNER trial, which examined the balloon-expandable Sapien (Edwards Lifesciences) valve, was the first one published. And the second reason is ease of use, as the balloon-expandable valve is the easiest valve to implant. Those two reasons contribute to why it is the dominant valve right now.

Healio: What do the current data tell us about the performance of balloon-expandable vs. self-expanding valves?

Stoler: Right now, there are not any good comparison studies. There are matched series, but none of them are definitive.

There is a trial underway called the SMART trial that will examine TAVR in the small annulus, and will randomly assign patients to either self-expanding or balloon-expandable valves. This will be fraught with some bias, however, and will be hotly debated when it comes out; the reason is because some people feel that it is not as wise to put the smallest balloon-expandable valve in if a self-expanding valve, which would be bigger, will fit in that small annulus. I think both sides will continue to argue regardless of what the data say.

In addition, there are constant comparisons looking for which valve is going to last the longest, along with many theories on both sides as to which one should last the longest and why. The issue with durability is that when we started performing TAVR, the patients who received the implant were all in clinical trials. Initially, the FDA would only let us treat those who were termed high risk or inoperable, and most of those patients were so sick or so old that they were not going to live 10 to 15 years; in fact, many of them didnt make it 5 years. So it has only been in the last 8 or so years that we have been implanting in patients who are healthy enough to outlive their valve. And when those patients are 10 or 12 or however many years out from the procedure, we will start to see how long these TAVR valves last and which, if either, will outlast the other.

Healio: Do you have any final thoughts on this topic?

Stoler: When the patient is chosen correctly and the valves are implanted correctly, both the self-expanding and balloon-expandable valves have great outcomes and appear to have durable outcomes as well. However, the decision of which TAVR valve to use and whether to do TAVR or surgical AVR has to be thought through intelligently with a heart surgeon and an interventional cardiologist looking at all the patient factors, including comorbidities and CT measurements. Therapy has to be individualized for each patient; that is what makes TAVR and surgical AVR such a good procedure. We tailor each valve to the patient, asking ourselves what fits, what is the upside, and are we more worried about coronaries or the patient needing a pacemaker or a bigger valve size. This is why we see these patients in a dedicated valve clinic, with surgeons, cardiologists and imaging specialists, so that we make a group decision on what is best for the patient.

For more information:

Robert C. Stoler, MD,can be reached at robert.stoler@bswhealth.org; Twitter: @rcstoler.

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