persistence. Despite their differences, there is immense overlap between the paroxysmal and persistent categories. In fact, some patients with persistent AF may revert to a paroxysmal disease state after receiving treatment. The tools for maintaining sinus rhythm have been the same for many years: 1) direct-current cardioversion to convert patients from AF to sinus rhythm and 2) anti-arrhythmic drugs (AADs) with a lousy risk/benefit ratio to maintain sinus rhythm over time. Studies have found that amiodarone is the most effective drug for maintaining sinus rhythm. The Canadian Trial of Atrial Fibrillation, for example, demonstrated that 65% of paroxysmal patients on amiodarone were arrhythmia-free over 16 months compared to 37% of those taking propafenone or sotalol, commonly used AADs with fewer extra-cardiac side effects.8 Despite the low rate of success with AADs, the rate of side effects over time is higher than for other classes of medicine. Approximately 30% of patients in a recent meta-analysis of AAD trials had a significant clinical side effect, and some patient deaths were attributed to AAD use.9 The efficacy of the newest AAD to come to market (dronedarone) is only comparable to the non-amiodarone medications, and may be worse.10
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iven the problems with AADs, it is easy to understand why nonpharmacologic approaches to AF, such as ablation therapy, have risen to prominence. Support for ablation therapy, which modifies abnormally functioning cardiac tissue, has come from two main sources. The first was the introduction of the Maze surgical procedure in the 1980s. For the “cutand-sew” Maze, surgeons made a series of cuts into the tissue of both atria and then sewed the cuts back together. The idea was to disrupt abnormal electrical impulses and reentry phenomena in the atria, allowing sinus impulses to funnel down to the atrioventricular node and then to the ventricles. Properly done Maze procedures were shown to have good results.11 After some cardiolo20 Fall 2015
gists, newly branded as cardiac electrophysiologists (EPs), began trying various ablation technologies to cure basic arrhythmias like atrial flutter and supraventricular tachycardia, AF became an obsession. The second milestone in the evolution of AF ablation came in the late 1990s 7 from a group of EPs in France led by Dr. Michel Haissaguerre. His name bears referencing because many of the concepts employed in modern complex arrhythmia ablation have come from his group. In a landmark clinical study by Haissaguerre’s group, patients with paroxysmal AF had electrode catheters placed in several locations within the atrial chambers, including the pulmonary veins.7 The investigators waited for medically facilitated episodes of AF to occur and found that the common sites of origin were within one or more of the pulmonary veins that connect to the left atrium.7 This finding led to the pulmonary vein isolation (PVI) procedure. In this procedure, surgeons use catheter ablation to create scar tissue around the pulmonary veins. Because scar tissue is not electrically conductive, the idea is that abnormal signals being generated within the veins cannot influence the remainder of the heart. Two recent studies of patients with paroxysmal AF have shown that catheter ablation is better than AAD therapy for maintaining sinus rhythm over two years.12,13 These and other results have elevated catheter ablation to a first-line therapy for treatment of symptomatic patients with paroxysmal AF. Ablation of patients with persistent and even longstanding persistent AF has also been included as a reasonable approach in current guidelines for managing AF.6 In cardiac electrophysiology, catheter ablation is done either with heat or freezing, also known as Fire and Ice.14 Fire refers to the use of radiofrequency current to heat up and modify the cardiac tissue of interest. Ice refers to the use of catheter balloons filled with nitrous oxide and cooled to below freezing. These tools are applied on the endocardial surface of the heart using catheters that allow for movement in
and around every part of the heart. The comparative efficacy of fire or ice is still under investigation.
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ill pulmonary vein isolation always be the standard for AF ablation? Will there be more specific ablation approaches allowing for shorter procedures with greater success? These are the questions being asked by EPs in 2015. A concept ca l led FIR M (foca l impulse and rotor mapping) was introduced a few years ago with much fanfare in the EP community.15 FIRM involves broad mapping of both atria with a large catheter to look for specific areas driving AF episodes outside of the pulmonary veins. Initial results were awe-inspiring. Not surprisingly, realworld use has proven less promising, but the concept got many wheels spinning. Now the Haissaguerre group is studying a way to place electrodes on the body surface to map the surface of the heart and look for areas driving AF episodes.16 Another group of scientists is investigating ways to use cardiac imaging to find areas of atrial scar that may participate in driving arrhythmia.17 Finally, treating AF isn’t all about the technology. In fact, recent research in clinical EP has shown that lifestyle modification is hugely important for AF patients. One recent study compared frequency of AF episodes among overweight patients who successfully lost weight vs. those who did not.18 The results showed a startling six-fold reduction in episodes among those who lost more than 10% of their body weight. Another recent study paints a similar picture for AF patients who comply with a structured regimen of cardioendurance training.19 There is also a close connection between AF severity and obstructive sleep apnea.20 Awareness of sleep apnea and counseling about weight loss stand to help as many patients with AF as catheter ablation might. In 2015, treatment for AF is much different than during my residency about a decade ago. EPs now have good ideas about how to treat this Sonoma Medicine