![]() ![]() Another difference was that the 2 AF groups showed significant conduction delay on optical mapping and fibrosis and collagen-gene up-regulation compared with the AFL group. The left atrial volume increased in the 2 AF groups but not the AFL group. The induced AF with an intercaval line had shorter CLs (cycle lengths) and substantial irregularity as compared with the AFL group. But, the duration of induced AF was greater in the 2 AF cohorts but not the AFL group. ![]() Each AF and AFL group also demonstrated an increase in AF vulnerability to AF induced with extra stimuli. The results of this study revealed that the effective refractory period was reduced similarly in each of the 3 AF and AFL groups as compared with the sinus rhythm control group. ![]() At the termination of the 3-week study period, each dog underwent extensive evaluation to determine the relative degrees of structural and electrical remodeling, including an echocardiogram and a terminal open-chest electrophysiology study. And, a final group of 6 dogs had the intercaval line created but remained in sinus rhythm for the duration of the study. A third cohort of 6 dogs had the intercaval line created for AFL but were in sustained AF. A second cohort of 6 dogs were in sustained AF and did not have an intercaval line created. A total of 24 dogs were divided into 4 cohorts and were intensively studied 3 weeks later. All dogs had an atrioventricular node ablation and ventricular pacemaker implanted and were paced at 80 beats/min. An intercaval radiofrequency lesion created a substrate for sustained isthmus dependent AFL in 3 of the 4 cohorts. ( 4) in this issue of the Journal, which uses an animal model of atrial flutter to compare atrial remodeling caused by AF with that caused by AFL. It is with this background that we consider the results of the study by Guichard et al. In contrast to the well-defined clinical features of AF compared with AFL, remarkably little is known about the relative impact of AF and AFL on atrial remodeling. And, AFL results in a regular rhythm, whereas AF is irregular. The stroke risk in patients with AFL is less than those with AF. AFL is harder to rate control and easier to ablate. But, we cannot forget the important differences between AF and AFL. This explains why one-third of patients effectively treated with ablation of the cavatricuspid isthmus developed clinically manifest AF at 15-month follow-up ( 3). These 2 rapid atrial arrhythmias are intertwined by the observation that without antecedent AF, AFL will rarely develop ( 1, 2). And, both respond to antiarrhythmic therapy or catheter ablation. They both can be treated with rate or rhythm control. They both can cause a rate-related cardiomyopathy. They both cause a range of symptoms including palpitations, fatigue, and exercise intolerance. They both are rapid upper chamber arrhythmias. From a clinical perspective, atrial fibrillation (AF) and atrial flutter (AFL) share many similarities. ![]()
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