Current status and outcomes of catheter ablation for atrial fibrillation Thomas Crawford, MD, Hakan Oral, MD From the Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, Michigan. Catheter ablation has evolved as an effective treatment modality in patients with AF. In this review, the rationale and outcomes of ablation strategies targeting various mechanisms of AF based on our current understanding are discussed. Likely mechanisms responsible for the therapeutic effects of these approaches are reviewed. KEYWORDS Atrial fibrillation; Catheter ablation; Outcomes ABBREVIATIONS AF = atrial fibrillation; APVI = antral pulmo- nary vein isolation; CFAE = complex fractionated atrial electro- gram; CPVA = circumferential pulmonary vein ablation; PV = pulmonary vein; PVI = pulmonary vein isolation (Heart Rhythm 2009;6:S12–S17) © 2009 Heart Rhythm Society. All rights reserved. Percutaneous catheter ablation was first attempted to mimic surgical Cox maze procedure in the right and left atria. 1,2 However, limited efficacy, high incidence of com- plications, and prolonged radiation exposure prohibited wide adoption. Since the recognition of the role that pul- monary veins (PVs) play in the initiation and perpetuation of atrial fibrillation (AF), 3,4 catheter ablation to eliminate AF has evolved rapidly over the last decade (Figure 1). Pulmonary veins Based on the seminal observation by Haissaguerre et al 5 that premature depolarization from the myocardial sleeves that extend into the PVs trigger AF, initial attempts primarily targeted arrhythmogenic activity within the PVs using a focal approach. 6 However, due to the risk of PV stenosis 7,8 and recurrences originating from other myocardial sleeves within the same and other PVs, complete electrical isolation of the PVs by segmental ostial ablation quickly replaced the focal approach (Figure 2). 9 –11 Several early studies reported a modest efficacy of approximately 60% to 70% of PV isolation by segmental ostial ablation in patients with par- oxysmal AF. However, this approach had minimal efficacy in patients with persistent AF. 10 Subsequently, circumferential PV ablation (CPVA), which involves applications of radiofrequency energy 1 to 2 cm away from the ostia of the PVs, except along the rim between the left-sided PVs and left atrial appendage with/ without linear lesions along the roof, mitral isthmus, and posterior left atrium between the encircling lesions sets, was proposed (Figure 2). 12 A key aspect of CPVA is elimination of all residual potentials within the encircling lesion sets. A randomized study demonstrated that CPVA had a superior efficacy than PV isolation by segmental ostial ablation in eliminating paroxysmal AF. 13 A number of ablation strate- gies have been described with variations in the technique, including wide area circumferential ablation, left atrial cir- cumferential ablation, and CPVA with confirmation of PV isolation using one or two multipolar ring catheters. 14,15 However, the premise of all of these strategies is ablation of a wide area around the PVs that extends well beyond the tubular portion of the PV. A randomized study demonstrated the efficacy of CPVA in patients with persistent AF. 16 Patients were randomized to CPVA or to up to two cardioversions with transient concom- itant antiarrhythmic drug therapy using amiodarone. CPVA was effective in eliminating AF in approximately 75% of patients with persistent AF. Maintenance of sinus rhythm was also associated with an improvement in left ventricular ejection fraction and quality of life and a reduction in left atrial size. Meanwhile, antral PV isolation (APVI) that targets all potentials within the PV antrum with an end-point of com- plete electrical isolation of the PVs has been reported to have a high efficacy both in patients with paroxysmal and in those with persistent AF (Figure 2). 17 Ablation strategies that target most or all of the PV antrum have a well-established efficacy for both paroxysmal and persistent AF that is superior than that achieved with PV isolation by segmental ostial ablation, suggesting that the PV antrum plays a critical role in the genesis of AF. PV antrum A histologic study from human embryo and fetuses dem- onstrated that most of the smooth potion of the endocardial aspect of the left atrial wall originates from the same PV Dr. Oral is a cofounder of Ablation Frontiers, Inc., and has served as a consultant to Ablation Frontiers, Inc. Dr. Oral has received research grants from St. Jude Medical, Boston Scientific, and Glaxo-Smith-Kline. Dr. Crawford has no conflict of interest to disclose. Address reprint requests and correspondence: Dr. Hakan Oral, Division of Cardiovascular Medicine, University of Michigan, CVC, SPC 5853, 1500 East Medical Center Drive, Ann Arbor, Michigan 48109-5853. E-mail address: oralh@umich.edu. 1547-5271/$ -see front matter © 2009 Heart Rhythm Society. All rights reserved. doi:10.1016/j.hrthm.2009.07.026