Access at: www.AERjournal.com Catheter ablation of AF has become an established therapy and may have the potential to cure this most commonly encountered sustained arrhythmia. Previous studies have demonstrated that pulmonary veins (PVs) are a major source of the ectopic beats that initiate AF. PV isolation in patients with symptomatic paroxysmal AF refractory to antiarrhythmic drugs is effective; however, it is difficult to eliminate all instances of AF. 1-3 If ectopic foci consistently come from a non-PV area and a pattern of spontaneous onset of AF is onset confirmed, the earliest ectopic site is defined as the non-PV trigger initiating AF. 2,4-7 Ectopy originating from non-PV areas can initiate AF and can cause it to recur after PV isolation. 4-31 Non-PV ablation after multiple AF ablation procedures decreases the risk of recurrence and increases the cure rate. 10,[19][20][21]23,25,28,29 Although several ablation strategies have been developed, the outcomes of ablation are not improved unless substrate modification targets AF triggers. 30 Taking all of these considerations into account, non-PV ectopy plays important role in both AF initiation and recurrence. 2,[4][5][6][7]20,29,30,[32][33][34] Mapping studies of non-PV foci have revealed that triggers are often found in anatomically predictable regions, such as the left atrial wall, thoracic veins and crista terminalis, and can be sustained or non-sustained triggers of AF. These areas can be mapped by specific multielectrode catheters positioned in key regions and ablated after the AF is induced and localised, or they can be ablated empirically without the induction of ectopy. 1-34 This review focuses on catheter ablation of AF initiated by non-PV triggers, summarising the electrophysiological characteristics, mapping and ablation strategies, their safety and efficacy. Several important concepts have been proposed regarding the role of non-PV ectopy in initiating AF. 2,4-7 AF is initiated by non-PV disturbance of the cardiac rhythm in up to 39 % of cases. 3,8-10,32-38 The left atrium (LA) (25.3 %), superior vena cava (SVC) (22.2 %), coronary sinus (CS) (18.0 %), right atrium (RA) including the crista terminalis (17.4 %),interatrial septum (7.9 %), and ligament of Marshall (LOM) (3.9 %) are the areas in which non-PV triggers of de novo AF are most commonly found ( Table 1), whereas the SVC, interatrial septum and LA are the most common non-PV trigger sites in recurrent AF ( Table 2). Furthermore, there is a higher incidence of non-PV triggers initiating AF in females and in patients with an enlarged LA. 39
PathophysiologyHistological analysis of the embryonic sinus venosus has identified areas capable of spontaneous depolarisation at the junctions between different embryonic tissues, such as the RA-SVC junction, crista terminalis and CS ostium. [40][41][42] The SVC is a major origin of non-PV triggers of AF. 5,8,[32][33][34][43][44][45][46][47] Heterogeneity of the SVC sleeve and arrhythmogenicity of cardiomyocytes isolated from the SVC have been reported. 41...
