Editorial Opinion: Finally, an Atrial Fibrillation Consensus Statement! Excerpts from the HRS/EHRA/ECAS Expert Consensus Sta

The expert consensus can be downloaded from the Heart Rhythm Society s Web site (www.hrsonline.org); it is available in the complete comprehensive version or a shortened and succinct Executive Summary. The comprehensive version extensively reviews all aspects of atrial fibrillation ablation, including the mechanism of AF itself. However, for the purposes of simplicity, I am providing the following consensus review, which will follow the outline of the Executive Summary. In this article, I will discuss the nuts and bolts of atrial fibrillation ablation in 2007. The Expert Consensus Statement defines atrial fibrillation into a variety of categories that are well known to the practicing electrophysiologist: paroxysmal, persistent, and permanent atrial fibrillation. Paroxysmal atrial fibrillation is that in which an individual has at least two episodes of recurrent AF that terminate spontaneously within seven days. Persistent atrial fibrillation lasts more than seven days (or less than seven days, but requires either antiarrhythmic drug therapy and/or cardioversion). A subcategory of persistent atrial fibrillation is that of longstanding atrial fibrillation, in which the episode of atrial fibrillation persists for more than one year. Permanent atrial fibrillation specifically refers to a group of patients who are not deemed to be candidates for atrial fibrillation ablation (either due to failed attempts at cardioversion or a decision not to pursue cardioversion). The Expert Consensus Statement documents the indications for the procedure and specifically outlines that it is not acceptable to consider catheter ablation for atrial fibrillation as a first-line therapy. Specifically, patients must have symptomatic atrial fibrillation that is refractory or intolerant to antiarrhythmic drug therapy. They define an exception to this guideline for those patients who have cardiomyopathy related to their AF; these patients may benefit from curative therapy to improve their reduced left ventricular ejection fraction. A contraindication for this procedure is the presence of a left atrial thrombus. In addition, treatment of asymptomatic AF for the benefit of stopping anticoagulation medications is an unacceptable indication for this procedure. Strategies for the approach to AF ablation are outlined in detail. The essential and central component is pulmonary vein isolation, since the majority of cases have pulmonary vein potentials as the trigger. In addition, the importance of documenting entrance and exit block from the pulmonary vein is highlighted. Avoidance of the pulmonary vein ostia with the application of ablative energy outside the pulmonary vein is an important factor in order to prevent pulmonary vein stenosis. Other triggers should be targeted only if they are identified as provoking atrial fibrillation; these other triggers, which occur much less frequently, can be identified in the superior vena cava, crista terminalis, fossa ovalis, posterior left atrial wall, coronary sinus, ligament of Marshall, and near the tricuspid and/or mitral valve annulus. Rarely, accessory pathway mediated tachycardia and/or AV node reentrant tachycardia can provide the trigger for atrial fibrillation. The Consensus Statement also outlines the importance of testing the completeness of linear ablations and/or circumscribed ablations in order to prove effectiveness of therapy. The role of cardiac imaging modalities, including nonfluoroscopic 3D mapping, intracardiac echocardiography, transesophageal echocardiography, CT scanning and/or MRIs, and esophageal monitoring are also discussed. The approach to anticoagulation in these patients has previously been described by the ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation.² A strict adherence to these guidelines is necessary in order to avoid thromboembolic complications (e.g., cerebrovascular accident/transient ischemic attack). In particular, the committee recommends that warfarin be implemented immediately following the procedure for at least two months, and that additional warfarin therapy be based on the presence of additional risk factors. Low molecular weight heparin should be utilized as a bridge to therapeutic warfarin therapy following the procedure. Finally, the discontinuation of warfarin is not recommended in patients who have a CHADs score greater than or equal to 2. The necessary training in atrial fibrillation ablation during fellowship has been reported to be a minimum of 30-50 AF ablative procedures. The committee believes that this number significantly underestimates the necessary training in which to perform these procedures independently. If an operator is to gain expertise while in clinical practice, additional training, supervision, and proficiency must be documented prior to independent performance. The committee is not skittish on emphasizing the importance of significant training and expertise, and specifically highlights this point. Post-ablation follow-up should be at a minimum of three months from the procedure (although in my opinion, it should be sooner, i.e., 2-4 weeks), and thereafter every six months for at least two years. During follow-up, event monitoring/loop recording might also be helpful to accurately document the presence or absence of recurrence. (An implantable loop recorder follow-up study is planned to identify recurrence following AF ablation.) The committee notes that during the three-month period following the ablation, there is an inflammatory response and a remodeling in which the operator should not consider recurrent atrial fibrillation a procedural failure. Many operators decide to treat the patients during this three-month period with empirical antiarrhythmic therapy. Outcomes status post atrial fibrillation ablation vary according to the category of the arrhythmia (paroxysmal versus persistent). Other risk factors may also play a role. The Consensus Statement summarizes the results of 23 nonrandomized and 5 randomized trials. Most nonrandomized trials demonstrated a 60% or greater single procedural success rate in patients with paroxysmal AF. The single procedural success decreases down to 30% or less in those with persistent atrial fibrillation. The results of randomized trials are summarized, but one observation is that it appears that AF ablation is better than empiric drug therapy as a whole. The overall clinical experience obtained from a survey of 180 centers and 9,000 atrial fibrillation ablation procedures notes that the average center performs approximately 38 AF ablation procedures per year. It is my opinion that this number of procedures per center each year is way too small for optimal proficiency in this technique. The reported success at a mean follow-up of 12 months in the survey was 52% without antiarrhythmic therapy and an additional 24% on antiarrhythmic therapy. The incidence of major complications was approximately six percent, and includes cerebrovascular accident/transient ischemic attack, atrio-esophageal fistula, cardiac tamponade, and pulmonary vein stenosis. The standard Cox-Maze surgical procedure, in which incisions are made to create a corridor of transport from the sinus node throughout the atrium into the AV node (without the ability to maintain atrial fibrillation), has been well described. Energy modalities utilized to perform surgical ablation include radiofrequency energy, cryoablation, microwave, and a high-intensity focus ultrasound. The majority of these procedures are performed in conjunction with concomitant surgical procedures (valve repairs and/or coronary artery bypass surgery). The indications for surgical AF ablation include symptomatic AF patients who are undergoing these concomitant surgical procedures, asymptomatic AF patients who may be undergoing cardiac surgery, and, in rare cases, as a stand-alone procedure for patients who have failed or are otherwise not a candidate for catheter ablation. Lastly, the Consensus Statement recommends waiting for at least three months to look for recurrence of atrial fibrillation. They define any recurrent atrial arrhythmia lasting 30 seconds or more as a recurrence. In conclusion, this document summarizes the current state of affairs with respect to surgical and catheter ablation procedures. At the present time, these guidelines should be followed by practicing electrophysiologists unless the procedures are being performed as a part of a research protocol. There are still many questions to be answered by catheter- and surgical-based methods of atrial fibrillation. Further refinement of both the technology and method is necessary in order to improve the outcomes of these procedures to eventually make them a first-line approach.