Insights into the Mechanism and Treatment of AF and Other Arrhythmias

This abstract oral session featured several researchers who reviewed (quite quickly) the results of their studies, focused on such topics as spatiotemporal behavior of high dominant frequency, isoproterenol agents, mistakes in the use of amiodarone and anticoagulation management, and 3D transesophageal ultrasound. Highlights of these studies are provided below.

Spontaneous Behaviour of High Dominant Frequency During Paroxysmal and Persistent Atrial Fibrillation in the Human Left AtriumJulian W Jarman, Tom Wong, Darrel P Francis, D. Wyn Davies, Prapa Kanagaratnam, Vias Markides, and Nicholas S Peters, St. Mary's Hospital & Imperial College, London, UKJarman and colleagues sought to systematically examine sites of high dominant frequency, as they have been thought "to indicate the location of drivers of atrial fibrillation" and "their spatiotemporal distribution and stability are critical to their relevance as targets for catheter ablation." After analyzing the non-contact electrograms that were recorded simultaneously from 256 left atrium sites during spontaneous AF, the team determined that focal areas of high dominant frequency peak "are more frequent in paroxysmal than persistent AF, are spatiotemporally unstable, are not the source of centrifugal activation, and are not therefore indicative of fixed drivers of AF." Further, they noted that in the "absence of spatiotemporal stability, successful ablation of sites of high DF cannot be explained as elimination of fixed driver sites."

Isoproterenol, but Not Vagomimetic Agents or Burst Pacing, Initiates Human Atrial Fibrillation by Steeping Action Potential Duration RestitutionDavid E. Krummen, and Sanjiv M. Narayan, University of California San Diego and VA Medical Center, San Diego, CAKrummen explained that he and Narayan conducted their research in order to determine if isoproterenol, adenosine, and rapid pacing "steepen left atrial (LA) action potential duration (APD) restitution and thus provide a mechanism for AF induction." Their results-which Krummen feels might "help guide new strategies to prevent AF initiation"-show that whereas isoproterenol "steepens maximum APD restitution, which may explain its pro-fibrillatory action in patients with persistent AF," adenosine and burst pacing "may initiate AF via alternative mechanisms involving focal triggers rather than reentry."

Mistakes in the Use of Amiodarone and Anticoagulation Management for Atrial Fibrillation: Why Do Cardiologists Deviate from Guidelines?Samuel Asirvatham, Mayo Clinic, Rochester, MN; Joseph S. Alpert, Arizona Health Science Center, Tucson, AZ; John R. Teerlink, University of California San Francisco, San Francisco, CA; and Eric N. Prystowsky, The Care Group, LLC, Indianapolis, INThis research was conducted in order to examine-using an online survey of 464 cardiologists-why management decisions are made that are contrary to the 2006 ACC/AHA/ECS guidelines for the management of atrial fibrillation, as the researchers felt that cardiologists recommendations vary when looking at anticoagulation and amiodarone use. Based on their findings, Asirvatham, et al. determined that education "is required to emphasize that CHADS2 score, rather than type of AF or symptomatology, should determine anticoagulation recommendations" and that "amiodarone should be a second-line agent regardless of patient symptomatology," as cardiologists "frequently deviate from established guidelines with regard to anticoagulation and amiodarone use for AF."

3D Transesophageal Ultrasound for Real-time Guidance of Atrial Fibrillation AblationsTimm Dickfeld, Magdi Saba, Jing Tian, Rishi Anand, Ahmed Hussein, Robert Peters, Stephen Shorofsky, and Christopher DeFilippi, University of Maryland, Baltimore, MDDickfeld and colleagues performed this study because they believed that the "inherent limitations of 3D mapping systems such as the simplified anatomy, registration errors, and the inability to reliably assess catheter contact or complications make real-time imaging a desirable component for atrial fibrillation (AF) ablations." What they found was that "3D ultrasound is able to provide unique anatomic real-time guidance during AF ablations and guide catheter contact at critical structures," suggesting a role for 3D ultrasound "in minimizing position errors inherent to 3D mapping systems and" possibly resulting "in improved procedural success."