A Decade of WATCHMAN™: Evolving Tools, Expanding Access, and the Future of Left Atrial Appendage Closure Therapy
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The Journal of Invasive Cardiology speaks with Chetan Huded, MD, about his experience with the WATCHMAN device (Boston Scientific).
WATCHMAN has been in the US market for 10 years and over a half million patients have been treated globally; how has your practice grown and evolved to adapt to the growing therapy demand?
We've seen steady growth in this space over the past several years. When the WATCHMAN FLX™ came out in 2020, we saw an uptick in procedural volume. In our practice, we've really had to continually work on day-to-day efficiencies to make sure we're treating all the patients who are referred for this therapy. We now have implanters on both the electrophysiology (EP) side and interventional cardiology side doing this procedure, and we think that's very valuable. We haven't siloed this into EP or interventional, we've maintained a broad range of expertise in seeing these patients.
I think that's critical for a couple of reasons. One, patients are referred from both disciplines, so we see patients on the interventional cardiology side with permanent atrial fibrillation (AFib) or older patients who are frail, with high bleeding risk. Conversely, our EP partners see a lot of patients who may be a bit lower risk, with paroxysmal AFib, who can't be on long-term anticoagulation, and are considering both rhythm control and appendage closure. So, we think maintaining both EP and interventional footprints in this space has been beneficial in terms of meeting the demand.
We've had to advocate to our administration that we think this therapy is a major part of the future of both EP and interventional cardiology. With that, our administration has been very supportive of giving us more lab time and more resources. And so, we've been able to meet the demand in the current approval climate. It will be interesting to see how this changes going forward, especially with new trials coming out.
Can you tell me more about specific obstacles your program has had to overcome to grow?
It’s a good question. So, in order to grow in most hospitals, you are borrowing time from something else, right? If program A grows, oftentimes that can be at the expense of program B or programs B and C, for instance. So we must continually make the case that this therapy is good for patients, that it's safe, that it's scalable, and that we have the patients to justify the lab time. As we see our volumes grow, we're continually trying to make sure we have enough Cath lab and EP lab time to do these procedures.
The other obstacle is that left atrial appendage occlusion is still primarily done with general anesthesia and transesophageal echocardiography (TEE), both nationally and within our practice. Growing a therapy like left atrial appendage occlusion requires an increase in a fairly complex number of necessary services—such as echo support, anesthesia support [post-anesthesia care unit] beds, and more. So that's a challenge and again, requires buy-in from the whole heart team. The whole team needs to feel that this is an important endeavor.
I think everybody sees the writing on the wall, that it's going to be hard to continue relying on transesophageal echo and general anesthesia if the volume continues to grow at the current pace. Right now, we're able to do it, but in the next 5 years, we may not. And so that's where solutions like ICE (intracardic echocardiography guidance) start to become more attractive. There's definitely a learning curve with ICE. We've gone up that learning curve. We have some operators who really have embraced it and specialized in it, we have others who are not interested in it, we have the whole spectrum. ICE is a technology that may be very important as the therapy grows to meet the needs of patients.
How has the OPTION Trial affected your belief in the therapy and overall patient selection for WATCHMAN?
It's interesting, and I think it can be confusing for people because the OPTION trial came out around the same time that concomitant ablation and left atrial appendage occlusion was approved for payment. And so I think people incorrectly believe that OPTION is a concomitant trial. It's not a concomitant ablation and LAAC trial. I look at it as the best data we have so far of a head-to-head comparison between oral anticoagulant (OAC) and the WATCHMAN FLX, across a large number of patients.
Although it's done in the context of patients who are getting rhythm control with an ablation, either concomitantly or staged (the population), what's being tested is OAC vs WATCHMAN FLX. What was very encouraging to me and really made me feel more confident in the therapy was that the ischemic stroke rate at 3 years in both arms is almost identical, it's just a touch over 1%. That has always been seen historically as a possible Achilles heel of left atrial appendage occlusion. There has always been this concern about an early ischemic stroke risk with the device compared to medical therapy.
Critics say that the device is intended to prevent ischemic stroke and, if there's a higher ischemic stroke rate with the device, well, that's a problem. What’s really encouraging to see in OPTION is that [ischemic stroke risk] no longer seems to be an issue. In the large number of patients randomized to OAC and WATCHMAN FLX, the ischemic stroke rate up to 3 years is nearly identical and it's very low. So, what I tell patients in the office is, can you still have a stroke after having a WATCHMAN? Yes, unfortunately, you can; but the reality is you can still have a stroke after being treated with oral anticoagulation. The residual stroke risk never goes to 0%, unfortunately, but both therapies seem to lower your risk to a very low rate (less than 1% per year). So, I feel very confident now in having this conversation with patients with very robust trial evidence behind it. It's going to be fascinating to see what CHAMPION-AF shows next year, and I'm optimistic and hopeful it'll show the same thing, which is that, compared with OAC, the WATCHMAN FLX is a very safe device and offers a very low residual stroke rate comparable to anticoagulation.
Considering CHAMPION-AF may increase the eligible patient population up to 4x, what would you tell your interventional cardiologist colleagues who are considering becoming WATCHMAN implanters?
A potential 4x increase in the population of patients referred for LAAC would be remarkable. I think it's within the realm of possibility. I don't think it'll happen overnight, but we are clearly going to need more people, more physicians to treat these patients. So, I would encourage people to take it on. Some of the most grateful patients are those for whom I’ve closed their left atrial appendage, and some of the most disappointed patients I’ve had are those for whom I’ve said, “I’m sorry, I couldn’t get a device to meet criteria.” It really is something that patients want, and I think the benefit from and the demand for LAAC is going to grow.
The challenge for interventional cardiologists is a couple things. Clearly, it's going to grow on the EP side; I don't think there's any question about that. With concomitant AFib ablation and appendage closure being approved now, that is a massive area for growth. I would love to see interventional cardiologists remain engaged in this space, especially those of us who are trained in structural heart disease, because it's a very natural evolution for a structural interventionalist. You get to take the skills that you use in terms of computed tomography (CT) modeling of the heart that you use all the time in transcatheter aortic valve replacement (TAVR) and apply those to the appendage. Skills that you use very commonly in navigating the left atrium for things like mitral transcatheter edge-to-edge repair (TEER), mitral valve replacement, and paravalvular leak closure are applied to left atrial appendage occlusion. When you marry those two skillsets together, it's a very natural procedure for people who've worked in this space.
As you said, if the therapy grows by 4 times, we're going to need all hands-on deck to make sure people are treated in a timely manner. I would encourage interventional cardiologists to stay engaged with the space. If you look at the data from the LAAC registry, there is a very large number of older, frail patients who have permanent AFib, who do not necessarily need an ablation. I don't see the world where this just grows into an EP-only procedure and interventional cardiologists have no role here; I think it’s the opposite. As the therapy grows, we need the EPs to focus on the people who need EP treatments, like ablations and concomitant procedures, and we're (ICs) going to need help to treat the patients for whom those are not part of the equation.
Recently, there were new left atrial appendage closure (LAAC) technologies launched in the United States, such as WATCHMAN FLX™ Pro LAAC Device and WATCHMAN TruSteer™ Access System. How have these devices impacted your ability to treat more patients with complex LAA anatomies?
I've been a very eager adopter of the TruSteer sheath. Even before TruSteer, the implant success with the WATCHMAN FLX was very high. In order to provide value, it was going to be very hard for TruSteer because you're already talking about a very successful procedure.
Despite that, I found it to be immensely valuable, and I'll explain what I mean: the other sheaths on the market are the WATCHMAN double-curve sheath and the WATCHMAN single-curve sheath, are both intended for a specific subset of left atrial appendage anatomies. The TruSteer sheath comes out of the box as a double-curve sheath, but it gives the operator the option of deflecting the tip in such a way that it can behave like a single-curve or a double-curve or, actually, go beyond the range of movements you could achieve with either of those sheaths independently. So, it's sort of like jumping to the final answer right away—you don't have to start with a guess and then work your way through an algorithm; you just go to the sheath that you know is going to give you the most degrees of freedom to treat the patient. I've been very happy with it.
I try to be cautiously skeptical of new technology. I ask, "Well, I'm gaining steerability, I'm gaining deflection, so what am I losing?” And I try to be careful about not assuming everything's win-win; it's not always like that. So I was very cautious early on, asking are we going to see more vascular complications? Are we going to see more pericardial effusions? Are we going to see more difficulty crossing the interatrial septum? I've been very pleasantly surprised that none of those issues were a reality. I've found it to be safe in terms of vascular access and easy to get across the septum without needing balloon septostomy. So far, I've not seen any uptick in things like pericardial effusion or bleeding in the procedure. The data from HEAL-LAA does show a statistically significant increase in procedural success with the TruSteer sheath, so I think that's been borne out in the clinical trial data.
The question I think sites need to ask is: is it worth the cost? Everything in medicine is going to ultimately come down to this question of value, right? Is the cost acceptable to justify the benefits? I think there are benefits, it’s just a matter of, in your local practice pattern, is that something that you can afford?
The WATCHMAN FLX Pro, which you brought up as well, added an expanded size matrix. So we have a 40-mm device now, which I can't say I use all the time. But, it does expand the pool of candidates who are eligible for the therapy, so I think that’s good. There are some changes to the coating of the device. In canine models, it seems to improve healing. We don't know yet completely whether there's going to be much benefit there in humans, but I applaud efforts to try to iterate the device, improve it, and make it safer, and lower the risk of device-related thrombus long-term. We have to see if that bears out in the data.
Are there particular anatomies which benefit more from using WATCHMAN TruSteer?
Great question. A straightforward left atrial appendage, or what we call a wind sock, which has adequate depth and coaxiality with the interatrial septum—those cases you can do with the prior generation fixed-curve sheath just fine. I don't think there's a major benefit, although there are small benefits in terms of coaxiality. The anatomies where the TruSteer really shines are very retro-flexed anterior chicken wings and very posteriorly and inferiorly directed appendages. Those are sort of opposite extremes, but they are the two appendages where it's the most challenging to get a fixed-curve sheath coaxial within the landing zone.
With a TruSteer sheath, because you can deflect the tip, with both of these extreme angulations you actually have a better chance of getting coaxial within the landing zone, which is, in my opinion, the most important thing to achieve seal. Thus, the TruSteer is particularly effective in anterior chicken wings and very posterior or inferior appendage shapes.
What would you tell your colleagues who are also WATCHMAN implanters about WATCHMAN TruSteer if they are considering trying it for the first time?
I encourage everybody to try it; I think it's very beneficial. I think there is a learning curve, like with any new technology, but it's not a severe or steep learning curve. I think in probably 5 to 10 cases most people have the hang of it. The things that I like about it are that it's purpose-built for this procedure. So, this is not a sheath that's built for, for instance, AFib ablation or mitral intervention that we're repurposing. It's dedicated for the WATCHMAN procedure. The knob is in an ergonomically favorable location and a lot of the tactile things are very similar to what you're used to. So, it's not a huge change from using a fixed-curve sheath.
It's worth being very thoughtful about the way in which you use it. I applaud Boston Scientific for the way they rolled it out; they had a very clear and prescriptive manner of teaching how to use the sheath. I won't go into the specifics of that, but there are times to roll the knob towards you and away from you, and they're not necessarily intuitive. So, a big part of the TruSteer sheath is relieving core wire bias. And when you do that after you've deployed the WATCHMAN, a lot of times it's actually rolling the wheel the opposite way you might expect. So, for an anterior chicken wing, you have the wheel rolled towards you to really extend it up anterior, deploy the device, and at the end you actually roll it away. So, you kind of do the opposite of what you might expect, you flex the tip down and that relieves some of the core wire bias. And so, there's some subtleties like that that are worth practicing the first few times. Once you get it, it's remarkable how much it helps.
At New York Valves this year, Boston Scientific’s next generation LAAC device was introduced. What are your initial impressions of WATCHMAN Elite™*?
My initial impressions are, I would say, optimistic. I am a firm believer that the success of the WATCHMAN device in this space is predicated on safety. The WATCHMAN FLX was a remarkable improvement in safety compared with the legacy WATCHMAN, the WATCHMAN 2.5. One of the reasons I'm optimistic about the next generation WATCHMAN is that it's built on the same platform, and I know the Research and Development team at Boston Scientific takes the safety of the device very seriously and so I don't expect we're going to see any backsliding on safety. In the current era, the procedure is remarkably safe; nothing is 100%, but the rates of major procedural complications are extremely low and certainly less than 1%. So, I'm optimistic that we're not going to see a major change in safety.
The question is why make a new device, why change it? The downside that we haven't talked about yet is that even in contemporary trials with the WATCHMAN FLX and the WATCHMAN FLX Pro, the rate of complete seal is still not where we want it. In HEAL-LAA, the 1-year complete seal rate was 85%, so we have approximately 15% of patients who have some degree of flow into the appendage, which is not our goal; our goal is a complete seal. So clearly, improvements are needed for that from a technology standpoint.
I think the new device has a couple of innovations that make a lot of sense. The thing I'm the most intrigued by is that the current WATCHMAN FLX Pro has a slight taper to the body (from the point of maximal diameter of the device to the back of the device). That creates a slight slant. The next generation device is going to have zero taper, which is expected to allow for a little better contact of the device deeper into the appendage. Oftentimes what we see on CT is that the device looks good, but the leaks happen because there's almost like a waterfall along the side of the device somewhere. And if you have less of a taper of the device, you can imagine it might improve sealing there.
I don't know what the data will show. However, I'm optimistic that it will be as safe as the device we have now, and maybe some of these structural changes with the architecture will improve the current 85% complete seal rate.
In addition to the zero taper of the device body, which I think is important, I understand there are slight changes to the actual strut architecture as well. There is a concept that the device may allow a little more filling of the distal appendage. I think it's something that we'll just have to learn as the device is in our hands and how it behaves.
As with the TruSteer, there's going to be a learning curve—any new technology has a learning curve, and so the trial is going to be important to figure out how these things actually play out in patients. I'm optimistic that the changes should move us in a positive direction.
The transcript has been edited for clarity and length.
