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| AATS/NHLBI: Cardiothoracic Surgery Exploring Collaborative Clinical Research Opportunities |
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Title and Author The Surgical Ablation for Atrial FibrillationRalph J. Damiano, Jr., MD Abstract Atrial fibrillation (AF) is the most common arrhythmia in the world, afflicting between 0.4 and 2% of the general population, and an estimated 6 million Americans. Moreover, it is commonly seen in patients referred for cardiac surgery. A recent study from our institution found that a third of patients referred for mitral valve surgery and over 20% of patients referred for aortic valve surgery had atrial fibrillation. The medical treatment of atrial fibrillation has been disappointing. Antiarrhythmic drugs have poor efficacy and a high incidence of side effects. Rate control and anticoagulation is often a disappointing strategy in the symptomatic and younger patient subgroups, and leaves patients at risk for a lifetime of anticoagulation-related complications. The poor results with medical therapy have led to the development of interventional approaches. The first successful interventional approach for AF was the Maze procedure, developed at our institution by Dr. James Cox and first introduced clinically in 1987. This procedure went on to become the gold standard for the treatment of AF, with an over 90% freedom from AF at late followup, both for the traditional cut-and-sew version and for the more recently developed ablation-assisted Cox-Maze procedure. The original cut-and-sew procedure was difficult to perform, and added significantly to both operative time and patient morbidity. Because of this, it was performed at only a few centers around the world. The field of surgical ablation has been radically transformed over the last decade with the introduction of ablation devices. This has made surgical AF ablation easier to perform, and has significantly increased the number of cases. Unfortunately, surgery for AF has gone from consisting of one very difficult operation performed very well in a few centers with high success rates to a plethora of many different procedures performed at many centers, often with poor results. A significant number of patients receive inadequate or illogical operations performed with inappropriate devices without proper indications. There are two major clinical problems hampering progress in the field. The first is that surgical ablation devices are being used off-label, and have been approved only for soft tissue ablation. They were released on the market in many cases without any experimental validation of their safety or efficacy for ablation of atrial tissue. The results have been predictable. There have been poor success rates, and many patients have been subjected to unnecessary and ineffective operations. A number of devices have been withdrawn from the market after being used on hundreds and in some cases thousands of patients after experimental and clinical demonstration of their inefficacy. These include two laser devices, microwave ablation and a number of dry unipolar radiofrequency devices. Moreover, collateral ablation damage to atrial tissue, coronary arteries and the esophagus has resulted in significant and avoidable patient morbidity. The next problem is that with the advent of ablation devices, there has been an introduction of a myriad of different lesion sets. Most of these were introduced clinically without experimental validation. This has led to a practice anarchy, and the belief that any atrial lesion pattern is appropriate for treating atrial fibrillation. This has been reinforced by the fact that many of these lesion patterns are termed a �mini-Maze� or �endo-Maze� and are still reimbursed, despite the lack of demonstration of clinical efficacy. Since most surgeons do not follow their patients long enough or carefully enough to determine their results, there has been no feedback mechanism to prevent this chaos. Moreover, the lack of randomized clinical trials comparing different lesion sets has let to a sort of intellectual nihilism among surgeons, in which some default to the easiest lesion set to perform (pulmonary vein isolation), even though its efficacy remains uncertain, and may actually be pro-arrhythmic. These problems need to be and should be addressed, both by the FDA and the NHLBI with more stringent pre-market testing of devices and the institution of randomized clinical trials. However, the most critical research gap in improving surgical ablation of AF is the fact that we do not understand the mechanisms of this arrhythmia in the individual patient. In order to develop a procedure that is as effective as or better than the Cox-Maze procedure with less invasiveness, it is imperative that we develop a mechanistic approach to each patient based on their individual atrial geometry and electrophysiology. It is well known that there are many different mechanisms underlying atrial fibrillation, and that these differ from patient to patient. Moreover, the mechanisms are known to change over time in the same patient. The major problem with our current operations is either that they are salvage procedures based on mechanisms that are not relevant in most patients (the Maze procedure) or based on an overly-simplistic targeting of triggers of atrial fibrillation (pulmonary vein isolation) which play little to no role in persistent atrial fibrillation and are often anatomically variable in location. It is critical that the NHLBI fund research to understand the mechanisms of atrial fibrillation and allow clinicians to define patient-specific AF phenotypes. This information could be used to create computer models to examine ablation efficacy before surgery and triage patients to appropriate treatment strategies. Without this mechanistic knowledge, we will continue to wander aimlessly without direction. Key Research Gap Requiring NHLBI Leadership An understanding of the mechanism of atrial fibrillation in each individual patient in order to develop a rational treatment strategy. Key Citations 1: Cox JL, Schuessler RB, D�Agostino JH Jr, Stone CM, Chang BC, Cain ME, Corr PB, Boineau JP: The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg 1991;101:569-5832: Prasad SM, Maniar HS, Camillo CJ, Schuessler RB, Boineau JP, Sundt TM III, Cox JL, Damiano RJ Jr: The Cox maze III procedure for atrial fibrillation: long-term efficacy in patients undergoing lone versus concomitant procedures. J Thorac Cardiovasc Surg 2003;126:1822-1828 3: Schuessler RB, Lee AM, Melby SJ, Voeller RK, Gaynor SL, Sakamoto S-I, Damiano RJ Jr: Animal studies of epicardial atrial ablation. Heart Rhythm 2009;6:S41-S45 |
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Copyright © 2012 American Association for Thoracic Surgery
All rights reserved. IMPORTANT REMINDER: The preceding information is intended only to provide
general guidance and not as a definitive basis for diagnosis or treatment in any particular case.
It is very important that you consult a doctor about any specific medical problem or question.
All rights reserved. IMPORTANT REMINDER: The preceding information is intended only to provide
general guidance and not as a definitive basis for diagnosis or treatment in any particular case.
It is very important that you consult a doctor about any specific medical problem or question.