Introduction Atrial fibrillation AF is

Introduction Atrial fibrillation (AF) is the most common cardiac arrhythmia encountered in clinical practice. The number of people with AF in the United States is currently estimated at 2.4 million, and the projected number with AF may exceed 10 million by 2050 [1,2]. Treatment for AF is also an important societal issue in that it represents a significant health care cost, currently estimated to be about €13.5 billion annually in the European Union [4]. Increased stroke risk in the presence of AF, reported to be an almost fivefold excess [5], makes AF more than a simple cardiovascular disease.
Patient selection according to the current guidelines It is important to recognize that the primary justification for an AF ablation procedure at this time is the presence of symptomatic AF, with the goal of improving patient quality of life [6]. Although other reasons for performing AF ablation may be justified, such as to decrease stroke risk [7], decrease Mitiglinide Calcium failure risk, and improve survival, they have not yet been systematically evaluated as part of a large randomized clinical trial and are therefore unproven. In the AFFIRM trial, there were no significant differences in the all-cause deaths between rhythm control and rate control using antiarrhythmic drug therapy [8]. However, the beneficial effect on the survival of restoration of sinus rhythm might be offset by the adverse effects of antiarrhythmic drugs. Therefore, sinus rhythm may be preferred over rate control if it can be achieved by catheter ablation. Large prospective multicenter randomized clinical trials will be needed to definitively determine whether sinus rhythm achieved with ablation techniques lowers morbidity and mortality as compared with rate control alone or treatment with antiarrhythmic therapy.
Patient selection and reverse remodeling after ablation Left atrial (LA) size has been established as a prognostic marker of cardiovascular morbidity, mortality, and stroke [9,10]. Studies have shown that LA enlargement and function can improve, i.e., “reverse remodeling,” after restoration of sinus rhythm from AF with certain medications or catheter interventions, including radiofrequency ablation [11–13]. A reduction in LA volume may lead to the improvement in LA function and exercise tolerance [14,15], decreased likelihood of thrombus formation [16], and decreased susceptibility to further atrial arrhythmias [13,17]. Although these benefits need to be proven by large randomized prospective trials, reverse remodeling after ablation appears to justify a more aggressive clinical approach even in less symptomatic patients. Currently, 2 studies have reported echocardiographic predictors, including LA strain and strain rate, of LA reverse remodeling after ablation [11,13]. It may be meaningful to select patients who are likely to achieve reverse remodeling as suitable candidates for catheter ablation of AF.
History of ablation strategies Segmental ostial ablation was the first catheter-based technique found to electrically isolate the PVs [18,19]. Ablation was performed at the ostia of the PVs, and the acute endpoint of PV isolation (PVI) could be reached in nearly every patient. However, the long-term success rates are relatively modest (60–70%). Circumferential PVI (almost equal to wide-area antral PVI), which involves creating circumferential lesions at the PV antra around the ipsilateral PVs, improved outcomes in patients with both paroxysmal and persistent AF (Fig. 1) [20]. The superiority of circumferential PVI over segmental PVI can be explained by the following: circumferential PVI may extinguish the triggers and drivers located in less common trigger sites other than the PVs, including the antral region of the PVs, the vein and ligament of Marshall, and the posterior LA wall. Circumferential PVI may impact not only triggers but also the arrhythmogenic substrate stabilizing the maintenance of AF [21]. The reduction of atrial muscle mass may make coexistence of multiple reentries impossible (debulking effect) [22]. Moreover, circumferential PVI may interrupt sympathetic and parasympathetic innervation from the autonomic ganglia, which have been identified as potential triggers for AF [23]. In a series of 349 consecutive patients undergoing circumferential PVI at the University of Michigan, AF was eliminated in 87% of patients with paroxysmal AF and 75% of patients with persistent AF [24].