Radiofrequency catheter ablation of atrioventricular nodal reentrant tachycardia: does the number of catheters matter?

Atrioventricular nodal reentrant tachycardia is the most common mechanism of paroxysmal supraventricular tachycardia in adults and is relatively uncommon in children. While the precise anatomy of the reentry circuit underlying AVNRT and relative role of the atrioventricular node and extranodal atrial inputs remain controversial, the electrophysiologic mechanism of the arrhythmia involving the concept of dual AV nodal physiology is now well recognized. According to this concept, functional dissociation of AV nodal conduction to the fast (fast conduction and long refractoriness) and slow (slow conduction and short refractori-ness) pathways serves as a key factor in sustaining reentry [1]. It has been demonstrated that the fast pathway conduction occurs superiorly in the region of His bundle recording, while conduction over the slow pathway is projected inferiorly over the coronary sinus ostium region, along the tricuspid annulus [2]. Recent evidence also suggests the presence of left-sided input to the AV node, and several case reports implicated left-sided reentry circuits in the mechanism of the AVNRT with successful ablation of the arrhythmia from the proximal coronary sinus or left side of the posterior septum, along the mitral annulus [3,4]. Although AVNRT is not a life-threatening arrhythmia, it can significantly affect the quality of life. Even in patients with infrequent symptomatic episodes, anticipation of arrhythmia recurrence may have considerable psychological impact on their everyday life. Prophylactic pharmacologic therapy with anti-arrhythmic agents is frequently ineffective or only marginally effective; moreover, long-term therapy with many of these agents is associated with the potential risk of side effects. Introduction of the catheter-based radiofrequency ablation technique into clinical practice in the late 1980s provided a non-surgical cu-rative option for treating AVNRT patients. The initial ablation technique targeted the fast pathway close to the His bundle recording site and was associated with a success rate of 80–90% and up to 23% risk of high grade AV block [5]. Subsequently it was replaced by targeting the slow pathway in the coronary sinus ostium region [6]. Currently, the reported acute success rate of the ablation procedure targeting the slow pathway is approaching 99% and depends in part on the endpoints of ablation that are used to declare success. The incidence of high grade AV block requiring pacemaker implantation is less than 1% [5]. In some AVNRT = atrioventricular nodal reentrant tachycardia rare instances of failed ablation from the right atrium, ablation of left-sided circuits by targeting proximal coronary sinus or left posterior …