Innovative New Atrial Fibrillation Catheter Procedures — Video of Robert Kowal, MD, PhD, FHRS
December 23, 2013
In this video from the Get in Rhythm. Stay in Rhythm.™ Atrial Fibrillation Patient Conference, Dr. Robert Kowal talked about innovative new procedures to treat atrial fibrillation and prevent strokes.
The ablation procedures he discussed included:
- Laser balloon
- Specialized radiofrequency catheters such as cycled phased RF
- FIRM (Focal Impulse and Rotor Modulation) Mapping
- Renal artery denervation
The stroke prevention devices that he discussed included the:
- Watchman left atrial occlusion device
- Lariat left atrial appendage closure
Video watching time is approximately 21 minutes.
About Robert Kowal, MD, PhD, FHRS
Dr. Robert Kowal graduated from Yale University and received his MD and PhD degrees from UT Southwestern Medical Center. He completed his medical internship, residency and cardiology fellowship at Harvard Medical School/Brigham and Women’s Hospital and went on to study cardiac electrophysiology.
He currently practices at Baylor Heart and Vascular Hospital. While performing a broad spectrum of device implantation procedures, from pacemakers to multi-lead defibrillators, his main focus is the management of complex arrhythmias such as atrial fibrillation and ventricular tachycardia. His approaches involve both non-invasive medical therapy and catheter-based ablation procedures. He has been and is currently involved in research on many cutting-edge technologies including cryoballoon ablation and FIRM mapping for atrial fibrillation, left atrial appendage closure and the role of renal denervation in the treatment of arrhythmia.
He has taken a national leadership role serving on the Board of Trustees at the Heart Rhythm Society and is on the editorial board of several scientific journals.
Knowing how important this information would be to those living with atrial fibrillation, we committed to do a two-camera video shoot of the entire conference—a very expensive undertaking—in hopes that you, the afib community, will be willing to help us defray those costs through a donation (instead of us charging you for these videos, which many of you said you were willing to pay for). You can make a secure tax-deductible donation here, or click on the red Donate Now button.
Mellanie: Now, we bring back to the podium Dr. Rob Kowal. Just a reminder—he is with the Baylor Heart and Vascular Hospital in Dallas, and is also a member of the Heart Rhythm Society Board of Trustees. He will be talking about some of the newer procedures. He does a lot of innovative stuff, and I asked him to talk about that as well as the left atrial appendage procedures that electrophysiologists do. So, let me bring up Dr. Kowal. Thank you.
Dr. Robert Kowal: Thanks. I’m going to shift a little bit in this talk and bring up what’s coming down the pike in newer technologies to treat afib from a variety of standpoints. I’ll start by saying that none of what I’m going to show you is completely FDA approved. When we’ve been working with these things, they’ve been on studies. They are coming soon to a theater near you, but not all of them are ready, although I’ll point out one or two things we’re doing in trials now that you can get involved with.
[1:15] To review where we’ve been in this discussion, this is the left atrium looking from the back. These are the pulmonary veins, as Dr. Rizvi pointed out. In paroxysmal atrial fibrillation, these stars represent these triggering sites in the vein and those trigger atrial fibrillation, and it’s trying to wall off those triggers that we’re trying to do. When you start moving to people who have atrial fibrillation for a longer duration, or are in it all the time—persistent atrial fibrillation—suddenly we’re trying to deal with a different beast here; it evolves. A lot of time, what’s going on is there are triggers in the atrium itself that are driving the atrial fibrillation. Some of these are focal sites, some of these are termed rotors—we don’t need to get into what that is; it’s kind of engineering 303—but needless to say, that’s our terminology for them. Part of the issue of developing new technology revolves around trying to better treat this transition.
[2:26] Let’s go back again—summarizing the last two slides—the two current approaches that are both done a lot, and FDA approved, involve using radiofrequency to make this point-by-point encircling of the veins, and this is a view of the left atrium from the inside, a 3D recreation, or using the balloon in one fell swoop to make that lesion around the veins. There are issues and limitations with each. One of the reasons why atrial fibrillation recurs is that when we’ve tried to isolate these pulmonary veins, we do an incomplete job, and little gaps can occur in where these points are, and afib can recur. Point by point, the limitation is that gaps are very common, and when you bring people back for a new procedure, it’s not uncommon that every vein has a gap. With cryoablation, it’s still seen, but less so.
[3:33] The other issue that makes these procedures hard is the gaps form because you can’t see where you are. You literally can’t visualize in the atrium what’s going on. The mapping systems help, but they’re still crude, and it’s not like looking at it. And you’ll hear from the surgeon in a bit—one of the great advantages of surgery is you can actually see what you’re doing and see the tissue. So, that’s a problem in both of these modalities. What about other targets? A second reason why the procedure fails—as I mentioned in the first slide—there are sites that can trigger atrial fibrillation, in a subset of people, that are not coming from the veins that are coming from elsewhere. [4:13] And the balloon can’t go after those, in the ways designed; radiofrequency catheters can, but it’s very hard to identify those. A lot of the new tools are designed to combat these limitations.
[4:31] The first one is something called the laser balloon. This is designed for treating people with paroxysmal atrial fibrillation. And this is a schematic of the balloon in the left atrium seated at the opening of the vein, ready to treat it. [4:47] The way it works is that it is a clear balloon that, from this point here, has a fiber optic cable that can emit a laser to cook the tissue locally and scar it. If you look from the shaft, this is the laser, and essentially you move that laser around the opening of the vein so that you can actually recreate what you do with radiofrequency, but with laser. [5:17] What’s neat about this is you can actually see where you are. This is pretty crude, but this is the tissue at the vein opening, and that is the vein opening itself. You can literally watch through a fiber optic cable and see exactly what you’re doing.
[5:34] This is under trials now. I think it has some promise, but it still has a couple limitations as well. I will talk about limitations a lot in this mainly because doctors want to see the evidence that things work and these are the questions you need to ask when you are confronted by the laser. New things that all sound good, you have to ask all the right questions. The limitations are it’s still point-to-point. So, even though you can see where you’re going, there’s still a risk of having gaps. Hopefully, those gaps are going to be fewer because of the fact that you can see where you are, and the other problem is you can’t target what we call non-PV targets, or non-pulmonary vein sites, these sites in the left atrium that could be triggering atrial fibrillation but can’t be attacked by going right around the veins. There are limitations, but still a promising new technology that we’re going to be hearing about. Probably, there will be more trials out very shortly.
[6:36] So, that is paroxysmal. Let’s look at what’s being done in persistent or long-standing persistent atrial fibrillation. And when you look at what we do now, there’s a variety of different approaches. And these are map diagrams—you’ve seen a little of this before of the left atrium with a different type of lesion sets, and what I mean by lesions is where these burns are being placed, and those are all represented by red dots. And what you can see, rather than in this approach, rather than just kind of circling around the veins, we’re really creating this kind of network of linear and curve lesions to try to get rid of afib by compartmentalizing areas. You’ll notice this is very reminiscent of what you’re going to hear about on the surgical side with what’s called the maze procedure. Essentially, this is electrophysiologists trying to recreate what has been defined in the surgery world, but with a catheter. This is an approach—I personally call this chicken pox; as you look at this, there’s red dots everywhere—and this is an attempt to actually not just empirically create lines and curves, but to try to target sites that look electrically like triggers of atrial fibrillation, and these are termed CFAEs. Again, not really important why they’re termed that, but that’s a term you will hear, and when you hear CFAE, it’s synonymous with trying to find sites responsible for triggering the atrial fibrillation.
[8:16] There are issues with these two approaches. These linear type lesions are difficult, and again, you still have these gap problems. So, anywhere along these burn areas, you can have gaps between the burns, and when you do, you can cause new rhythm problems. These CFAE sites, while it sounds great, are very poor and difficult to define, and we have different definitions of how we look for those, and it’s not completely uniform yet. The other general rule of thumb is that the more energy you deliver, either cryo or radiofrequency, the higher your risk of complications. The balance we face when doing these procedures is kind of knowing when to say when. If I keep burning, I may have a higher success rate, but I will definitely have a higher complication rate. That’s the balance we’re trying to strike during the procedure. [9:10] Then when you do these procedures and there are gaps, you have fairly high incidence of rhythm called left atrial flutter, and what that is is all these burns transform the fibrillation into a short circuit that is localized, but is still a short circuit. In most cases, that goes away. In some cases, that can be a worse problem from the standpoint of symptoms than the atrial fibrillation ever was. And so again, we have to balance what we do to try to prevent that.
[9:48] One approach to dealing with this is actually changing the tools we use. Under trial is a new set of catheters that tries to attack these different sites. It’s not a one-size-fits-all; it’s an approach that recognizes that there are different areas you’ve got to ablate, and so we need different tools for that. There’s a circular ablating and recording tool for the pulmonary veins, there’s this funny-looking thing that is used to treat one area of the atrium, and this one to kind of spot-welding of other areas in the atrium. This is under trial and it’s a combined toolset idea, which is very inviting. Thus far, there is six-month trial data showing with persistent atrial fibrillation about a 67% success rate, which is actually very good with that population. What came from the first trial though is an increased risk of stroke when using these tools compared to other tools. So, they’ve been redesigned, and they’re about to go through yet another trial to make sure it’s safe to use broadly. This is a study we may be starting up early next year called VICTORY, and more to come on that. So, this is one approach. [11:13] Again, limitation wise, there’s not an ability to kind of map where to go; you’re still kind of using this empirically.
[11:24] The other approach is to try to actually map where these sites are coming from. What I’m going to refer to now is something called FIRM mapping, which a lot of you may have heard about and we’ve had the pleasure of working with a bit. And the idea here is, if this is the chamber with atrial fibrillation, right now we record from individual sites; but in FIRM mapping, you put in catheters that have multiple electrodes in the form of a basket, and you record the whole chamber simultaneously. And then, from there, you run through complex signal processing algorithms to define where sites are the triggers—I mentioned they’re called rotors—and then you can localize where those are based on where that basket is, and then you burn those sites. [12:12] This is an example of the baskets sitting in the right atrium during one of our cases.
[12:17] I’m going to skip this because it’s long and doesn’t necessarily help explain it, but what’s the data to support this? The data is still small, and there’s a lot to learn about this, but it’s promising. The first published study is 92 people who had predominately persistent atrial fibrillation, and this was a comparison of patients who had pulmonary vein isolation, a traditional approach, versus pulmonary vein isolation plus this FIRM mapping to target additional sites. This is, again, one of these Kaplan-Meier curves, these success curves, now flipped over. So, a 100% success would be at the top and 0% success would be at the bottom. This is the people who got the standard approach, and this is the people, over time, who got the FIRM mapping with the standard approach, and overall did better.
What are the limitations with this? I think it’s very promising. The baskets are very unwieldy to use and there are new baskets being developed. That’s why this is partially FDA approved, but not fully. I think by first quarter of next year, we’re going to get a whole new set of tools to work with this, and we’re still waiting for a randomized trial to know exactly what the best patient group is for this technology.
[13:41] The last new thing is really a combination of two existing things. I’m really excited about this, and that is the concept that afib doesn’t exist in its own. As I had said before, you have high blood pressure, you have sleep apnea —all those things need to be treated or treating your afib doesn’t help. Well, this is a concept where you treat two things at once, and I’m going to take a step back.
[14:11] First, it’s a concept called renal denervation, and I’m going to do a little introduction. We all have something called the autonomic nervous system, and this is the most primitive nervous system in our bodies. It controls things that we don’t think about—breathing, heart rate, blood pressure—all those things are controlled on a second-by-second basis by the autonomic system. Turns out, the autonomic system also can negatively impact and cause atrial fibrillation, and one of the sites where the autonomic system is regulated is at the blood vessels that go to the kidneys. Kidneys are what cause us to urinate and filter, and [14:52] so this is a diagram of the kidney blood vessels here. And it’s a combination where the autonomic nervous system regulates those blood vessels, and then has sensors that sense flow through those kidneys that regulate it back. There has been a move in the high blood pressure world that if you do red dots—if you ablate not the heart, but these kidney vessels—you can affect high blood pressure in people, and it looks like it’s going to be very successful.
Well, the question that was asked was, “What if we combine this with atrial fibrillation?” Literally, as you’re pulling the catheter out of the body you do this. [15:30] What’s been found is that in 27 patients—this is small—with atrial fibrillation and high blood pressure, [15:40] when you did the pulmonary vein isolation with renal denervation, this ablation of the veins, you did far better than doing the pulmonary vein isolation alone. And in fact, you also lowered the blood pressure. Is it just a blood pressure effect? Are you actually affecting the afib? We don’t know yet. We are pleased that we’re a part of a trial that’s enrolling at Baylor Heart and Vascular to actually look at this, and this is a national trial. It’s actually a very special national trial because there is no company sponsor. It is physicians who are running this trial, and it’s a very aggressive trial, and a new way of doing things.
[16:22] I quickly want to talk about what’s coming in the realm of devices to prevent stroke. We’ve all heard about stroke being an important target. We’ve all heard about the various drugs to prevent stroke. The question that is being asked is can we actually avoid drugs? So, where do strokes come from? This is an ultrasound image of the heart. This is the left atrium, and this is a structure called the left atrial appendage; and in fact, this is a little out-pouching where blood clots are believed to form that then break off and cause the stroke. The question then is can we prevent the stroke by sealing off that left atrial appendage with some type of device? [17:11] One device being tested is called the Watchman device. It looks like an umbrella or a parachute. And the details are not that important, but it’s made of a pliable metal called nitinol. [17:26] This is an example of how it goes in: we put a catheter in that appendage, we then size it, pick the right device, and then that sits in there, and the story doesn’t end there. You still need blood thinners for a little bit of time because what happens then is the body kind of heals over this area and fibroses it closed, so that eventually, that seals up, and now three or four months after the procedure, you can stop the blood thinner. That is very effective.
[18:01] I’m going to focus on this graph here. What this is is a randomized study looking at warfarin, a traditional blood thinner, versus this occlusion device and looking at the end point of disabling events. These are events that are strokes or bleeds that truly disabled someone. What you see—and these are events for every 100 patient year—and what you can see is there are fewer than half the number of events with the device than there are with warfarin, depending where you look along the course of the trial. This has been measured out over two years, so it’s very promising.
[18:40] There are limitations. It takes several weeks for the appendage to close; it’s not easy to do these. You’re going to need to find people when these come out who are used to doing it. And like I said, it’s not yet FDA approved.
[18:55] An alternative approach to this is something called the LARIAT procedure. I’m just going to go through this quickly. This is a snare from the outside of the heart. [19:08] What we do, we get access under the rib cage to the area outside the heart, and then we get access inside the heart, and then we get little wires that, using a magnet, connect, and [19:23] then that snare is placed over that wire to lead to occluding the appendage. [19:31] What’s emerged from that is about, of all the patients we look at who could be eligible for this, about 70% can actually get their left atrial appendage occluded with this approach. And if that does happen, the likelihood of staying closed and occluded is very high, in the 98% range.
[19:53] Limitation-wise, again, these are complicated procedures—they’re not easy to do; they&rrsquo;re not yet FDA approved; and now, when you go outside the heart, you introduce some new complications, like some chest pain from outside the heart.
[20:08] To close, the general conclusions just from take homes from this are that there are now, and will continue to be, new tools that will be developed to make afib ablation easier to do, safer to do, and hopefully more successful. I think the other approach is that stroke prevention is going to be evolving, too. When I have patients who say to me, “Am I stuck on Coumadin for the rest of my life?” what I say is, “It’s redefined—we’re going to have a stroke prevention strategy for you for the rest of your life, but that may change, and it may change every few years in how we do that.”