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    • The so called driver hypothesis has been posited in

    2019-06-15

    The so-called driver angiotensin receptor blocker has been posited in the recent years. Optical mapping studies in isolated sheep hearts have suggested that at least some cases of AF can be maintained by high-frequency reentrant sources (rotors), usually located in the posterior LA, which result in spatially distributed frequency gradients [69,70]. High-frequency rotors maintain AF through fibrillatory conduction to the remainder of the atria. From the clinical point of view, in patients with paroxysmal AF, this hypothesis is supported by the fact that high-frequency activity within the PV continues even after the restoration of sinus rhythm in the atria [71]. Presence of a left-to-right atrial frequency gradient in patients with paroxysmal AF also supports this hypothesis [72]. In persistent AF, however, electrophysiologists experience some responses of AF dynamics to ablation that are not consistent with the findings estimated from the driver hypothesis. For example, there is no left-to-right atrial frequency gradient in patients with persistent AF [72]. It is rare to find sites of DFmax in the PV region, and isolated PV tachycardia after restoration of sinus rhythm in the atria has never been observed. A cumulative effect is frequently observed in ablation of persistent AF. Haïssaguerre et al. reported that although stepwise ablation was performed in a randomized order (PVI, atrial ablation, and coronary sinus/superior vena cava ablation), the number of patients with termination of AF increased as these procedural steps were completed [47]. It is a common finding that sites where radiofrequency application terminated AF had been previously ablated [73]. Taken together, it is difficult for the driver hypothesis alone to explain the findings observed during the procedure. One of the possibilities that can account for these findings might be the presence of multiple AF drivers, but this has not been proven in humans.
    Complications Because the major purpose of catheter ablation of AF is to improve patients\' quality of life, and its efficacy in improving survival has not been proven, the probability and severity of complications related to AF ablation must be recognized by all electrophysiologists, and patients should only undergo AF ablation after carefully weighing the risks and benefits of the procedure. Because AF ablation is one of the most complex interventional procedures performed, the risk associated with zygospore procedure is estimated to be higher than that of the procedures to treat other arrhythmias. Although prospective studies surveying the mortality rates associated with AF ablation procedures are lacking, a worldwide retrospective survey of prevalence and causes of fatal outcomes in AF ablation reported that lethal adverse events occurred in 0.1% of patients undergoing AF ablation [74]. Major causes of fatal outcomes were tamponade, stroke, and atrioesophageal fistula. More recently, predictors of complications and 30-day readmissions were identified from the data from the California State Inpatient Database [75]. Five percent of patients experienced periprocedural complications, and almost 10% were rehospitalized within 30 days. One patient died during the index admission, and 9 patients died during the 30-day rehospitalization, resulting in a mortality rate of 0.24%. These rates are quite high when one considers that AF itself is not a life-threatening arrhythmia. Oral et al. reported that AF ablation is associated with early postprocedure thromboembolism, regardless of both the postprocedure rhythm and whether the patient has risk factors for stroke. The most likely cause was thought to be char and/or thrombus formation at sites of LA endocardial ablation, and the probability was 1.0% [76]. Thus, heparin anticoagulation with close attention to maintaining a therapeutic dose (activated clotting time (ACT) of at least 300–350s) during the procedure is important. Data regarding the risk of thromboembolism with and without warfarin after AF ablation is limited. Because symptomatic or asymptomatic AF may recur during long-term follow-up after an AF ablation procedure [31], discontinuation of warfarin therapy post-ablation generally is not recommended in patients who have a CHADS2 score ≥2 [6]. Although the use of dabigatran has increased in clinical practice, an observational study with a matched-control design reported that periprocedural dabigatran use significantly increased the risk of bleeding or thromboembolic complications compared with uninterrupted warfarin therapy in patients undergoing AF ablation [77]. Large randomized controlled studies are required to confirm this result.