MD Conference Express AHA 2011 - (Page 20)

n SELECTED UPD ATES I N ATRI AL FI BRILLATION New Horizons in Atrial Fibrillation Written by Rita Buckley Biology, Genetics, and Management of AF At a joint session of the AHA and ESC, Stanley Nattel, MD, Montreal Heart Institute, Montreal, Canada, discussed the biology and genetics of atrial fibrillation (AF) as the basis for understanding and managing the condition. AF can occur due to multiple underlying factors, including heart disease, disturbances in extrinsic regulation, and genetic abnormalities. Development of AF requires an ectopic trigger activity and reentrant substrates to permit the maintenance of the arrhythmia. In many (probably most) cases, the occurrence and manifestations of AF are determined by multiple contributors that act in concert. Chronic coronary artery disease (CAD) is a significant risk factor for AF, increasing the risk 3-fold postmyocardial infarction [Krahn AD et al. Am J Med 1995]. Nishida et al. recently determined the effects of chronic ischemia/infarction on AF-related substrates in an animal model, providing novel insights into potential underlying mechanisms of AF in patients with CAD [Nishida K et al. Circulation 2011]. Wang et al. identified the Pitx2 homeobox gene (a gene that contains a short DNA sequence), which is involved in the development of the myocardial sleeve around pulmonary veins, as a key player in many forms of AF [Wang J et al. Proc Natl Acad Sci USA 2010]. In another study, Body et al. found that noncoding single-nucleotide polymorphisms (SNPs) within the chromosome 4q25 region are independently associated with postoperative AF after coronary artery bypass grafting [Body SC et al. Circ Cardiovasc Genet 2009]. Whether these new clinical and genetic discoveries will translate into meaningful changes in clinicians’ ability to predict which patients will develop AF or which patients will respond to prevention or active therapies remains unknown but is actively being pursued. Ablation of AF – How, When, and What Else? Ablation is the only proven treatment that is capable of eliminating AF in a substantial proportion of patients. Hakan Oral, MD, University of Michigan, Ann Arbor, Michigan, USA, discussed how and when catheter ablation should be initiated for the treatment of AF. Targeting the underlying mechanisms is imperative for successful treatment with catheter ablation. These include addressing the arrhythmogenicity of pulmonary and other thoracic veins; autonomic dysregulation; fixed and/or functional reentry with fibrillatory conduction, including multiple wavelets and high frequency sources (eg, rotors); and electroanatomical remodeling [HRS/EHRA/ECAS Expert Consensus Statement. Heart Rhythm 2007]. Pulmonary veins have a dominant role in AF [Haissaguerre M et al. N Engl J Med 1998]. Therefore, ablation strategies that target the pulmonary veins and/or the antrum with the goal of complete electrical isolation are the cornerstone for most AF procedures. For surgical pulmonary vein isolation, entrance and/or exit blocks should be demonstrated [Heart Rhythm Society Guidelines. Heart Rhythm 2007]. Peer-Reviewed Highlights from the scientificsessions.org my.americanheart.org Patients with AF of longer duration, such as those with persistent or permanent AF, may require targeting of additional sites (eg, left atrium, coronary sinus, superior vena cava, ganglionated plexi, and complex fractionated atrial electrograms). Data show that use of this tailored approach eliminated paroxysmal AF in approximately 80% of patients [Oral H et al. Circulation 2006]. Despite these advances, the long-term efficacy of catheter ablation to prevent recurrent AF requires further study. The totality of data suggests that www.mdconferencexpress.com 20 January 2012  http://www.mdconferencexpress.com http://my.americanheart.org/professional/Sessions/ScientificSessions/Scientific-Sessions_UCM_316900_SubHomePage.jsp http://www.scientificsessions.org http://my.americanheart.org http://www.mdconferencexpress.com

Table of Contents for the Digital Edition of MD Conference Express AHA 2011

MD Conference Express AHA 2011

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