Atrial Fibrillation: Ablation of Atrial Fibrillation
Guest: Dr. Marcus Wharton – Clinical Cardiac Electrophysiology
Host: Dr. Pam Morris - Cell Biology & Anatomy
Dr. Pam Morris: Hi, this is Dr. Pam Morris. I am here today talking about atrial fibrillation with Dr. Marcus Wharton who is professor of Medicine and director of Cardiac Electrophysiology at the Medical University of South Carolina. Marcus, you are known around the world for your technical skill in a procedure known as ablation of atrial fibrillation. Just exactly what is this procedure?
Dr. Marcus Wharton: It is a complex procedure but a very exciting new therapeutic option for most patients with symptomatic atrial fibrillation. Atrial fibrillation, to understand what we do with the procedure, you have to understand a little bit about what causes atrial fibrillation in the majority of individuals who have it. It is complex. It requires a little bit of understanding about the anatomy, particularly within the left atrium, or the left upper chamber, of the heart. As you may recall from your school days, after the blood goes through the lungs and has picked up oxygen, it drains through veins into the left atrium and from the left atrium, it goes to the left ventricle and gets pumped out to the body so the body can use it. The pulmonary veins are the veins that drain the blood back from the lungs and connect into the atrium; there are typically four of these. Where they connect into the atrium there is a muscular sleeve, or coat, of atrial tissue that reflects up onto the vein and goes up into the lung tissue itself for a distance of a couple of inches.
The reason why this anatomy is important, there is something about this tissue in people who develop atrial fibrillation that they develop little cells in those muscular coats on top of the pulmonary veins, the lung veins. They have the capability of electrically discharging, or firing, at a very rapid rate, 300, 400, 500 beats per minute, maybe just for just for 5 or 10 beats. But, it goes so fast that it puts the heart into atrial fibrillation. Or, in some people, it may put them into another related rhythm called atrial flutter. Why some people have it, other people do not, we really do not know. It is a huge area of investigation right now. These muscular sleeves that coat the pulmonary veins where they join into the atrium are responsible for the great majority of episodes of atrial fibrillation that a person experiences.
What we do, if you go in with several different catheters going to different places in the heart but, in particular, two of those catheters go through a plastic tube called a sheath, we can take from the vein in your leg and up into the right atrium using a special technique to poke a hole through the septum so we can then deliver the catheter, or the sheath, to the left atrium. Then, using that catheter, we can then burn a big, sort of, circle around where the veins drain in. This electrically, basically, disconnects the muscle going up into the lung vein where the atrial fibrillation originates and keeps it from being able to communicate with the rest of the atrium. So, even though the little sites that are buried up there in this tissue may continue to fire intermittently, they cannot get to the atrium. They are kind of put in jail, in a fashion. And since they cannot get out, they cannot cause atrial fibrillation.
Dr. Pam Morris: Sort of like putting up a road block there, you have burned the tissue and created an electrical road block.
Dr. Marcus Wharton: We did, exactly. We disconnect, electrically, the tissue from one another. Now, people frequently ask, that sounds bad, you know, you are disconnecting part of my atrium, does that impact on my heart function? And, actually, it does not. We have seen from studies, actually, that if atrial fibrillation is contributing to a decrease in your heart function, your heart function actually improves after an ablation procedure. But, there is no measurable decrease in function from the ablation procedure itself.
Dr. Pam Morris: Now, how do you decide in whom to perform ablation? We talked in an earlier podcast about some of the various medical options that would seem, certainly, simpler. But, there must be certain patients for whom these medications are not effective and you need to go to a more interventional approach.
Dr. Marcus Wharton: As we mentioned, actually in the previous discussion, the medicines that we give rarely cure a person in terms of eliminating episodes. And, typically, even when we get a good response with medications, with the stronger anti-arrhythmic medications, for suppression of atrial fibrillation, that response tends to be time-limited. So, the patient may have a response for a year or two, or three, but then for whatever reason, and we do not understand this phenomena very well, they stop responding to a drug. We have an option at that point of trying another drug of a different category perhaps, to see if we can get a response there or proceeding to an alternative approach which would be catheter ablation, nowadays. So, in terms of a specific answer to your question, the people who have atrial fibrillation who are candidates for an ablation procedure or patients who have symptomatic atrial fibrillation, so you have symptoms of palpitations or shortness of breath or dizziness related to your atrial fibrillation and patients who have been tried on at least one medication, one anti-arrhythmic medication or drug like Propafenone or Flecainide, Sotalol, Dofetilide, Amiodarone for suppression of your atrial fibrillation. These categories have been picked because in those patients you have drugs, it has not worked, the risk of the procedure seems appropriate.
There is some research being done of using catheter ablation as what we call front-line therapy. So, once you have atrial fibrillation, rather than progressing to medications which have a low probability of curing the problem, you can go directly to a curative procedure. But, we don not have enough data from control clinical trials at this point in time to say that that is the best approach in most patients.
Dr. Pam Morris: You use the word curative. How frequently does the ablation procedure completely solve the problem permanently?
Dr. Marcus Wharton: In cases of patients who have paroxysmal atrial fibrillation, where the atrial fibrillation starts and stops on its own, the cure rates are very high. It depends on which studies you look at. But, if we take your data from the Medical University of South Carolina, the cure rate for a single procedure is about 85 percent. If we do something called a touch-up procedure, say, if you have a recurrence or if you are in that 15 percent of patients who does have recurrence after the initial procedure, we go with a second procedure and kind of touch up anything that came back from the first procedure and we can cure most of those. So, with one or two procedures in a patient with paroxysmal atrial fibrillation, the cure rate runs about 98, 99 percent.
If you have persistent atrial fibrillation, the results drop down a little bit, to maybe 75, 80 percent, for a single procedure. If you have chronic atrial fibrillation, you have been in atrial fibrillation, by definition, for greater than a year and your doctors have tried to get you out and cannot get you back into a normal rhythm, the results are much less and the techniques are less well evolved because that becomes a more global process. It is no longer just confined to the lung veins themselves. The disease, or atrial fibrillation, causes damage to both the right and the left atrium and that causes disease throughout the atria, which we also have to address with the ablation procedure.
Dr. Pam Morris: That would seem to indicate, then, that a decision to proceed with ablation should be made within the first year of the onset of atrial fibrillation?
Dr. Marcus Wharton: I do not know if necessarily the first year, but early on. What we want to do nowadays is we can change what we call a natural history, or the rate of progression, of atrial fibrillation by earlier intervention with catheter ablation techniques. So, we want to catch a person while we have the highest probability of curing that person. So, clearly that is when they are in this paroxysmal stage or, really, if they are in the persistent stage. But, if they are allowed to stay in chronic atrial fibrillation for two or three years and then come to see us, we still have some improvement with the procedure, some cure rates, even, with the procedure. But, it is not near as good at the stage in the game. So, we really would like to be catching people earlier on in the disease process, before they have been allowed to stay in atrial fibrillation for a long period of time.
Dr. Pam Morris: Now, let’s assume we have a patient who has decided to go ahead with the ablation of atrial fibrillation. What can they expect, for example, on the day of the procedure?
Dr. Marcus Wharton: I cannot say it is a simple procedure. It is a fairly long procedure. It takes, on the average, probably about five hours. From a patient’s perspective though, they come into the hospital, they check in and we put them onto the examination table, the catheterization table, put them to sleep with something we call conscious sedation. That is where we give them drugs that, I say, put them in la-la land so they really do not care. And that is really all they remember until they wake up at the end of the procedure. They recover overnight in the hospital and go home to following day.
In terms of restrictions after an ablation procedure, it takes a few punctures to get the catheters in, these are typically in the veins in your leg so there is some tenderness there. But, in terms of the only restrictions after, just no heavy lifting or straining, or golfing, or tennis for five days after. So, try to keep those puncture sites in the leg from bleeding because they [patients] will be on blood thinner after the procedure to decrease clots from forming around the areas that we have burned in the atrium, which predisposes to bleeding at the puncture sites in their legs. So, they cannot do any heavy lifting or exercise. But, other than that, people go back to work a couple days later or they certainly can drive and walk around town and do paper work, and things like that. So, it is a relatively simple procedure.
Dr. Pam Morris: Are any follow-up studies necessary after the procedure?
Dr. Marcus Wharton: We routinely see everybody back at four months. It takes awhile. The procedure is a relatively large procedure in terms of the damage it does to the heart. You can imagine that we are burning a fairly large portion of the atrium which causes inflammation as the body tries to heal the areas that are burned. That can cause all sorts of rhythm problems that will go away in a period of about four or five weeks after the procedure, very similar to what happens after open heart surgery where the surgeons have been into the heart sac and caused irritation and damage from the surgical procedures, kind of what we call inflammatory atrial arrhythmias. So, they stay on their medicines awhile, their anti- arrhythmic medications, for several weeks and then we see them back at four months. At that point in time, we start making the assessment about whether or not they are cured from their atrial fibrillation, from the procedure. We do a period of monitoring for about a month and if they have no symptomatic or asymptomatic atrial fibrillation, we then make the decision to stop their anti-coagulation as well. So, it is not immediately after the procedure. They do not come off of all their medications, it is kind of a gradual pulling off of medications as they get further away and have had a chance to heal up from their procedure.
Dr. Pam Morris: Now, you mentioned earlier on, they remain on their blood thinner, but that is also discontinued, ultimately?
Dr. Marcus Wharton: In most patients, the goal is, one, get them off their anti- arrhythmic medications and, two, to get them off of their anti-coagulants. Clearly though, patients, where we have to be cautious in this regard, so if they have had prior history of stroke, we may wait a longer period of time to make sure that they are indeed cured, not just in the first six months but, say, maybe after a couple years of follow-up. Their risk, if we are wrong, for having recurrent stroke would be high. So, there are certain individuals who may wait longer before we make the decision to withdraw warfarin. But, in the majority of patients, the goal is to get them off their anti- arrhythmic drugs and their warfarin therapy as well.
Dr. Pam Morris: Are there any long-term complications of this procedure? When you are consenting a patient, what are the things you inform them of as potential risks?
Dr. Marcus Wharton: Well, the biggest single complication related to the procedure is bleeding from the puncture sites, as I have already alluded to. So, we just tell them to take it easy on their legs. Around here, it is tough because everybody likes to play golf when they have a few days off and that is a terrible thing to do after you have had an ablation procedure. They will get back to the golf course in due time. But, in terms of complications, late complications, the biggest single late complication we worry about is something called pulmonary vein stenosis. This is late formation of strictures in the lung veins as a consequence of burning in the lung veins, or ablating within the lung veins, occurring several months after the procedure. That used to be a huge limitation to the procedure. It used to occur in anywhere from 4 to 20 percent of patients, depending on what type of studies you want to look at, with the older techniques.
But, with the present techniques, that is vanishingly rare. It really has been relegated to the point of being kind of a historical interest, not to say that it cannot happen. But, it is very unusual for that to happen now because we no longer burn, or ablate, within the vein. But, we burn, or ablate, outside the vein, in the atrial tissue, a much wider area of exclusion. And that specifically evolved in order to avoid this complication of pulmonary vein stenosis, or stricturing.
Dr. Pam Morris: We mentioned earlier that many of these patients may have coronary heart disease or plaque build-up in the arteries as a risk factor for atrial fibrillation. Are there any complications, such as heart attack, from a procedure like ablation?
Dr. Marcus Wharton: Sure, if patients have baseline obstruction in an artery, the stress of the procedure may be enough to precipitate a heart attack. That is, fortunately, a very unusual complication. In terms of the biggest single acute complication occurring during the procedure, or within a couple hours after the procedure, is perforation of the heart, something called cardiac tamponade. It is where a small hole is made at the sites where we are burning and, because the patient is on blood thinner, they bleed into the heart sac surrounding the heart. That puts pressure on the heart so that it cannot pump adequately. It causes the blood pressure to drop and that is an emergency which requires us to stop the procedure and drain the fluid off of the heart. That is a serious complication, whenever we put catheters into the left atrium. Fortunately, it is not very common. But, it is one of the things that your doctor has to consider when they are considering atrial fibrillation ablation versus medical therapy as a potential risk of the procedure.
If we look at all the different types of complications, though, associated with an atrial fibrillation ablation, the overall risk of a complication is relatively high. It is six percent, although most of that is bleeding complication from the puncture sites that require a visit to your doctor, or a visit to the emergency room, within a few days after the procedure. In terms of serious complications, like the perforation of the heart, heart attack, stroke or pulmonary vein stenosis, the risk of that, most major centers doing atrial fibrillation ablation at this point in time, runs about one to two percent. So, that sounds fairly high compared to what we think about with medical therapy. But, actually, if you look at the risk of medical therapy, there are sort of unrecognized risks with anti-arrhythmic drugs, in particular, for suppression of atrial fibrillation.
There is a study called the Affirm trial that randomized patients to receive either anti- arrhythmic drugs or rate-controlling medications. What they showed was that mortality was increased in the group of patients, and they had risk factors for stroke, treated with anti-arrhythmic drugs. This raises the overall concern that we have with long-term use of anti-arrhythmic drugs. They may actually pose a risk of dying of abnormal ventricular arrhythmias which can be fatal. The other thing that has come out of the AFFIRM trial and several other medical trials using anti- arrhythmic drugs is that the risk of cancer and potentially lung disease as well is increased for reasons that we do not understand well. So, catheter ablation has an associated risk, anti-arrhythmic drugs likewise have an associated risk. The risks of catheter ablation are upfront because they are related to the procedure at the time of the procedure. The risks of anti-arrhythmic drugs are kind of amortized over time. They keep accumulating for the duration of your exposure to the drug.
So, there are concerns now, within the scientific community, that perhaps catheter ablation is actually safer than medical therapy. There is a trial ongoing right now called the Cabana trials, sponsored by the National Institutes of Health, which is a mortality trial with the expectation being that the hypothesis driving the trial is that catheter ablation will actually result in an improvement in survival compared to medical therapy. It is obviously too premature right now to say that that is the case because we do not have the results from the CABANA trial. But, we do have the results from several retrospective trials that have shown, or suggested at least, an improvement in survival with catheter ablation compared to medical therapy despite the risk of the procedure itself.
Dr. Pam Morris: You know, not to mention the quality of life improvement associated with catheter ablation in the sense that the ultimate ability to discontinue medications with complications, such as the blood thinner itself, and not to mention the relief of symptoms.
Dr. Marcus Wharton: Yes, it is quite amazing actually. The quality of life is something we can say very firmly in terms of we have good prospective trials that have shown improvement of quality of life and its improvement in terms of one’s physical sense of well being. It is also an improvement in one’s perceived mental functioning. That is because anti-arrhythmic drugs and the rate-controlling medications impact our ability to exercise. Also, particularly in the older patient populations, they can decrease their mental functioning or their perception of mental functioning. So, drugs have a very profound effect, potentially, on the quality of life that an individual experiences. It is one of the joys that I have of my job, that I see these people in follow-up after they have had a catheter ablation and they have been allowed to come off their medications, and they come back and they go, you know, I just did not know that I could feel this way, I thought I was just getting older and this is the way you feel when you get older. But, they realize that once you stop the drugs, it is the way drugs make you feel. It is a nice alternative nowadays for improving the quality of life of most individuals besides chronic medical therapy.
Dr. Pam Morris: I know that you have a very long wait list for this procedure and that the Medical University is now one of the top two referral centers for the procedure for ablation of atrial fibrillation. I, for one, am very grateful that we have your expertise here for this technique and I thank you for coming to talk with us about this today.
Dr. Marcus Wharton: Thank you.
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