Atrial fibrillation ablation in concomitant cardiac surgical patients

INTERVIEW Filip Casselman Atrial fibrillation ablation in concomitant cardiac surgical patients Surgical treatment of atrial fibrillation tailored to concomitant cardiac surgical patients has developed steadily, with the introduction of new technologies further expanding the role of the cardiac surgeon in managing this disease. Confluence caught up with Filip Casselman, Cardiac Surgeon at OLV Ziekenhuis Aalst, Belgium, to discuss a new decision pathway and how it will influence patient care and outcomes. How often are atrial fibrillation (AF) and mitral valve problems associated? Mitral valve disease is often related to AF. 1 When we speak about concomitant patients we speak about cardiac surgical candidates who have a problem that needs to be treated surgically and who also have AF. It appears that in the course of mitral valve disease initially there is a problem with the mitral valve but, as time goes on especially if it is mitral regurgitation the pressure on the left atrium increases and patients are more likely to develop AF. We do also see AF in stenotic patients, but the reason I emphasize the regurgitation is that currently in Western European countries, where I practise, we see far more mitral regurgitation than mitral stenosis. However, in developing countries where rheumatic heart disease is still prevalent, you will also see AF develop in mitral stenosis patients. Indeed, AF is actually a marker of progressive mitral valve disease. Early in the course of the disease, you may have a patient without AF, but with increasing regurgitant mitral orifice area and volumes, chances of developing AF increase as markedly as other cardiac adverse events, reaching a global incidence of 62% at 5 years in patients with an effective regurgitant orifice area of at least 40 mm 2. 2 You say that treatment is important; could you give us a brief history of how AF has been treated in the past? At the start of cardiac surgery, patients presenting for surgery who were also in AF only had their primary cardiac disease corrected. Indeed, AF was very common, as patients presented later in disease progression compared with today. In addition, there was no treatment available to correct the AF and the clinical consequences of AF were less well known than today. As time went on, people started to realize that AF was, as I said, a marker for progressive disease, but one that also had important consequences. So what are the consequences? Why does stroke occur? It is at least partially related to the irregular heartbeat: the loss of regular atrial contraction leads to partial stagnation of blood in the left atrium and especially in the left atrial appendage, which is a blind sac attached to the left atrium where clot formation can occur. This clot may then dislocate and progress within the bloodstream to other parts of the body. In addition, outcomes after various cardiac operations are negatively influenced by the presence of AF. 3-6 As soon as people started to realize this, they also started to think about management. The very first treatment options were developed by a surgeon named Dr James Cox. He developed a surgical strategy in the eighties, which was optimized in the early nineties and is still applicable today. It was known at that time through basic studies that the atrial tissue needs a certain surface for AF to persist. Dr Cox developed a way of creating what we call electrical barriers in both the left and the right atria using what we call the cut-and-sew technique. This technique makes incisions in the left and right atrium which are then resutured. 7 This became known as the Cox-Maze technique. The healing process created scar tissue and this proved to be an electrical barrier. So AF could still originate, but could not persist because the reduced individual atrial surface areas created through the cutting and sewing meant that AF could not propagate further into the heart, 29

fig. 1 Endocavitary application of the cryoprobe to create an inferior pulmonary line (scar tissue) fig. 2 Endoscopic epicardial view showing the transmurality of the endocardially applied left isthmus lesion fig. 3 Final view of the minimally invasive cryo-maze (atrial fibrillation ablation) procedure Image reproduced from Heart, Casselman FP et al, 91:791-4, copyright notice 2013, with permission from BMJ Publishing Group Ltd irrespective of the mechanism of origin of AF (local firing focus or multiple wavelet theory). For almost 15 years, this was the standard procedure. However, it is quite an extensive procedure, and people often said it was too difficult, although I disagree on this latter point. So when other technical tools became available to create these electrical barriers, the treatment of AF really took a step forward. These different treatment options involved heating or cooling, all with the purpose of creating scar tissue to act as an electrical barrier, thus respecting the original principles of the Cox-Maze procedure. At the same time, cardiologists started to create some of these lesions endovascularly with catheterbased techniques. How are patients treated today and what role does the heart team play in deciding optimal management approaches? All concomitant patients are discussed within the heart team at our centre. On the whole, patients who present with lone AF without other major surgical indications are generally treated by cardiologists, because these patients mainly have paroxysmal and persistent AF. The story is different if they have long-standing persistent AF. Furthermore, if a patient requires an operation, they would generally be directed towards surgery regardless of the form of AF they have. Our task as surgeons is, therefore, to treat every patient and their associated AF. Concomitant AF implies that there is also a surgical indication, so the way the surgery is performed depends primarily on the initial surgical indication. If a centre performs a lot of minimally invasive heart surgery or if a patient comes for aortic valve surgery, or mitral and tricuspid valve surgery, these patients are treated minimally invasively. However, if a patient needs an extensive heart operation, such as for example aortic and mitral valve surgery and a coronary artery bypass graft (CABG) on top of that, then this will be done through standard sternotomy. However, overall we do have a lot of tools today that enable us to treat AF in a minimally invasive manner (figures 1 3). Are there any patients in whom surgical management of AF is contraindicated? Those with very enlarged atria or very elderly patients. What I want to stress is that, in my mind, the duration of AF does not play a role as long as the size of the atrium is acceptable. We often hear This patient has had AF for ten years, there is no advantage in treating this. I disagree completely with this statement. If patients have had AF for ten years, but with only moderately enlarged atria, they remain perfect candidates for AF surgery. In my opinion, the size and histology of the atrial wall are much more important than the specific duration of the AF. There is some discussion regarding the size of the left atrium at which the effectiveness drops below acceptable standards. A lot of people make a 30

cut-off at 6.5 cm diameter. However, this is just because it is a statistical value in a study; it does not mean that surgery in people with a 7 cm left atrium would be unsuccessful, but the percentage of success will decrease as the size of the atrium increases. The success rate will never drop from 100% to zero but it will drop from 90% to 80% to 70% to 60%, or even to 30%, with increasing atrial size. However, it is relatively exceptional to see huge atria in Europe. In Belgium, for example, we rarely see patients with atria above 6.5 cm. On the other hand, if someone presents with rheumatic valve disease, as can be the case in developing countries or in other parts of the world, huge atria may coexist and the surgeon needs to realize that the success rate will be less optimal. What guides the choice of instrument (scalpel, cold or heat) used to make the scar tissue in the atria? The alternative energy sources make the ablation procedure easier and faster, but obviously we need to make sure that we have good results. The most important point is that we have to create transmurality with whichever instrument is chosen. The wall of the atrium has a certain thickness and the scar tissue needs to be through the whole thickness of the tissue. The tool that we choose will depend on its track record in terms of producing the transmural lesion. Nowadays, we have evidence that certain tools are able to create transmural lesions and others are not, so it is extremely important that we use an appropriate tool. This being said, the familiarity of the team or the surgeon with one device or another will also play a role in the choice of a certain technique. Another issue that is more and more important in today s medicine is obviously cost. Some devices are more expensive than others. Sometimes we need two devices to create all the lesions of the original Cox-Maze procedure, which obviously will increase cost. Consequently this may also play a role in choosing one technique or another. What does the perfect AF surgery outcome look like? This depends on the status of the patient and also the type of AF. If we have a patient coming for concomitant surgery and paroxysmal AF, we can treat this patient successfully in more than 95% of cases; we have a very, very good chance of total success. If a patient comes in with long-standing persistent AF, the chances of success will be lower, simply because the AF is at a more advanced stage and the disease will have had repercussions on the structure and histology of the atrial wall, so that it is more difficult to reverse the process. This is also the reason why in more complex forms of AF we need a more extensive lesion set in order to increase the chances of success. So, for example, with paroxysmal AF, we can have a success rate above 95%, diminishing to about 65 70% in long-standing persistent AF for simplified lesion sets. But if we increase the lesion sets, then for these people with long-standing persistent AF we can have a success rate up to 80 85% at three or four years now, as seen in our series. With more complex disease we need a more complex lesion set in order to optimize outcome. This increase in success rate comes at the expense of about 25 minutes extra operative time. What are the potential complications of this surgery? There are few potential drawbacks for cases of paroxysmal AF, though the technique used can have complications. The left atrium is close to the oesophagus and the use of extreme temperatures cold or heat has caused injuries in the past. This is now very seldom because people don t use those specific energy sources any more. The cryotherapy we currently use has very few adverse events reported to date. 8 The main drawback is that if patients have had long-standing persistent AF, the sinus node has been lazy for several years. What we very often see post-operatively in these patients is that the AF is gone, but there is no regular heartbeat. Normally, after a few days, the sinus node starts to pick up again. On rare occasions, the sinus node is not able to pick up the heart rhythm and these patients then will need a permanent pacemaker, despite the fact that they are out of AF. What rehabilitation is required after surgery? The addition of an AF ablation does not add time to the rehabilitation. Rehabilitation time will primarily depend on the initial surgical indication, and will obviously be shorter in minimally invasive procedures versus standard sternotomy approaches. 31

Why have you chosen to develop a decision tree to guide treatment of AF with concomitant mitral valve disease? The first reason is that in daily practice, we still see surgeons who are reluctant to treat AF. There are different reasons for that. Sometimes surgeons are not very familiar with the complex pathophysiology behind AF. That is because in the past, rhythm disturbances were mainly treated with medication by cardiologists and only later became relevant for surgeons. If someone is not comfortable with the disease, they may feel some reluctance to perform such a procedure. A second reason is that Dr Cox used both left and right atrial incision patterns regardless of the type of AF. However, it appears that not all forms of AF need the full lesion set. Therefore, some surgeons have advocated reducing the number of lesions without decreasing results, while lowering the complexity and duration of the surgery. However, when we reduce the number of lesions we sometimes also reduce the results of the procedure, with recurrence of AF some time post-operatively. For optimal results, choice of the correct lesion set is vital. We therefore felt that it was important to develop a practical decision tree to guide surgeons about when they should or shouldn t perform AF surgery and also about how extensive the lesion set should be for a given patient or AF type. What does the decision tree look like? We have tried to make it relatively simple; it is actually also based on an editorial of Dr Cox.9 We have added a number of clinical parameters and target measurements to that, in order to help surgeons to decide whether to perform AF surgery (or, in exceptional cases, when not to) and, above all, which lesion set to perform in a given patient. The major variables to take into account are the type of AF and the size of the left and right atrium. This is quite new because a lot of people still focus only on the left atrium and we think that there is not enough attention given to the right atrium. Very often, if we are unsuccessful, we find the reason in the right atrium. That is very important for physicians to realize. The right atrium is important because, while AF usually originates from the left atrium in the majority of patients, it sometimes also originates from the right atrium. If we only treat the left atrium in such patients, then we will not see a successful outcome. Recent advances have shown that mild tricuspid valve regurgitation also needs to be treated aggressively and I think although it is not proven scientifically yet that if we are more aggressive with the tricuspid valve and then consequently also with ablating the right atrium, success rates of our ablation procedures will increase. Who has been involved in the development of the decision tree? This is a European collaboration between five centres. The initial initiative was sponsored by Medtronic Inc., who asked different people who practice AF surgery to meet and to produce this decision tree, so it is mainly a surgery-oriented initiative. Clearly the decision tree is going to help guide surgeons, but what is going to be the benefit for patients of having this decision tree? First of all, the goal of the decision tree is to eliminate the reluctance of any surgeon to treat AF. Of course there may be some exceptional cases, but more than 90% of these patients should get an arrhythmic procedure. That is obviously a benefit for the patients. If they have AF they should be treated. Almost no patient with AF should leave the operating room without treatment. If their AF is treated correctly they should experience the benefit of elimination of potential complications related to AF. Secondly, related to the type of AF, we hope to offer the surgeons the choice between a less extensive or a more extensive lesion set in order to increase the success rate of surgical ablation. These days we see quite regularly that surgeons have applied the reduced lesion set to any type of AF. They may have very good results in the more simple forms of AF, but the results will be less optimal in the more complicated forms of AF. Consequently, the patient should benefit a second time from the decision tree. Do you intend to publish the decision tree? It is not published yet as we are in the final stages of developing it. We still need to approve the final format, but we are close. Prior to publication, we would like to demonstrate the validity of the decision tree in clinical practice in the different 32

Address for correspondence Filip P. Casselman, MD, PhD, FETCS Department of Cardiovascular and Thoracic Surgery OLV Clinic Moorselbaan 164 9300 Aalst Belgium Filip.Casselman@olvz-aalst.be centres involved in its development. However, we certainly hope to publish it in due course. What future data are needed in this area? As I mentioned, providing evidence for the decision tree would be very valuable. Furthermore, what is very important with any type of AF surgery, regardless whether or not the decision tree is used, is the fact that we need to follow these patients over the years. That s easier said than done. A lot of these patients feel good and don t want to come back for a regular followup after treatment. According to the guidelines by different rhythm associations, both surgical and cardiological, we would need to carry out a yearly Holter monitoring in all these patients over 24 hours, but ideally over seven days. You can imagine that not many patients are very keen to do that. That is one of the difficulties we face, but it is very important because we need to have an indication of how these patients behave in the longer term. When we follow-up these patients they may be perfectly well for three or four years and then have a relapse. If they have a relapse, it is important to study them to see why it occurred, so that lessons can be learnt and applied in clinical practice. Moreover, surgeons usually do not follow these patients for more than a year; follow-up is logically often carried out by the referring cardiologist. I would, therefore, like to stimulate everyone involved to keep following these patients with Holter monitoring even though they are doing well or have a sinus rhythm on their electrocardiogram. The follow-up after five years is very scarce and we would love to see longer follow-up. Ultimately, we would like to have better pre-operative assessments of the patients, including mapping techniques and visualization techniques, so that we can better guide specific treatment to a specific patient. For example, if a patient has a lot of fibrosis and scar tissue in the atrial wall, we suspect that such an atrium is less likely to regain a nice contracting pattern, which remains the ultimate goal: abolish the AF and recreate a nice contracting pattern. Indeed, if we abolish AF but the atrium is not contracting nicely, we have not abolished the possibility of clot formation. In conclusion, as you can derive from our interview, AF is an interesting pathology in which there is still room for improvement in its workup and management, in order to optimize outcomes for the benefit of patients. REFERENCES: 1. Avierinos JF, et al. Circulation 2002;106:1355-61. 2. Enriquez-Sarano M, et al. N Engl J Med 2005;352:875-83. 3. Mariscalco G, et al. Circulation Oct 14 2008;118(16):1612-18. 4. Ngaage DL, et al. Ann Thorac Surg 2006;82(4):1392-9. 5. Ngaage DL, et al. Ann Thorac Surg 2007;84(2):434-42. 6. Villareal RP, et al. J Am Coll Cardiol 2004;43(5):742-8. 7. Cox JL, et al. Semin Thorac Cardiovasc Surg 2000;12(1):15-19. 8. Gammie JS, et al. Ann Thorac Surg 2009;87:1452-9. 9. Cox JL. J Thorac Cardiovasc Surg 2010;139(6):1374-86. DISCLOSURES: The opinions and factual claims herein are solely those of the author/interviewee and do not necessarily reflect those of the publisher, Editor-in-Chief, Editorial Board and supporting company. FC acts as a Consultant for Medtronic Inc. and for Edwards. 33