In clinical practice, the earliest local ventricular or atrial activation will identify the accessory pathway insertion site. Importantly, the number of RF energy applications necessary for successful pathway ablation is lower if an accessory pathway potential can be identified. Generally, pacing maneuvers at atrial and ventricular sites are used to dissociate the pathway potential from the atrial and ventricular electrograms. In manifest pathways, the distal bipolar recording at the successful ablation site will demonstrate a discrete, low-amplitude accessory pathway potential between the local atrial and ventricular electrogram that precedes the onset of the delta wave on the surface ECG ( Figure 123-2 ). The most reliable mapping criterion is the recording of an accessory pathway potential. Catheter stability is verified by less than 20% variation in the atrial potential amplitude. Ventricular myocardium is relatively thick at the atrioventricular groove, resulting in an atrial-to-ventricular-signal amplitude ratio less than 1, whereas a position at the atrial insertion site has a ratio of approximately 1 and a position at the ventricular insertion site a ratio of 1/2 to 1/6. 22 The presence of additional accessory pathways may be evident only after ablation of the first, or it might be suggested during intracardiac mapping by variations in the activation sequence because of simultaneous or alternating conduction across multiple pathways.Īccurate localization of an accessory pathway will require careful intracardiac mapping during the electrophysiology study. Multiple accessory pathways can occur in up to 13% (see Figure 123-1) of patients with the WPW syndrome and its prevalence is as high as 52% in patients with Ebstein anomaly. These alterations in repolarization are caused by cardiac memory and require no further treatment resolving spontaneously over time. 20įollowing successful catheter ablation, the 12-lead surface ECG commonly demonstrates repolarization changes in the direction of the delta wave. 20 In a prospective evaluation of 121 patients, the authors could demonstrate that the vector of the initial portion of the surface delta wave in leads I, II, aVF, and V1, as well as the R-to-S ratio in lead III and V1 accurately predicted 1 of 10 sites around the atrioventricular annuli or subepicardial region with a sensitivity of 90% and a specificity of 99%. 20 developed an algorithm for accessory pathway localization correlating the surface 12-lead ECG pattern with the successful ablation site in 135 patients with manifest anterogradely conducting pathways. The 12-lead surface electrocardiogram (ECG) will aid in pathway localization and preparation for the best ablation strategy. Rarely, an accessory pathway spans from the atrium (atriofascicular), AV node (nodofascicular or nodoventricular), or His bundle (His-fascicular) to a more distal branch of the His-Purkinje system or the ventricular musculature. Accessory Pathway LocalizationĪccessory pathways are commonly located along the tricuspid or mitral annulus or within the subepicardial pyramidal space in the inferoseptal region ( Figure 123-1 ), forming connections between atrial and ventricular tissue.
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Of Mental Disorders-fourth edition text revision, India, pathway to care. The main source of referrals were school teachers and general medical practitioners. Karl-Heinz Kuck, in Cardiac Electrophysiology: From Cell to Bedside (Sixth Edition), 2014 Ablation of Supraventricular TachyarrhythmiasĮrik Wissner.