Electroanatomical activation mapping of koch's triangle vs anatomical and electrogram based slow pathway ablation in typical atrioventricular nodal reentrant tachycardia: a comparative analysis

Background Typical atrioventricular nodal reentrant tachycardia (AVNRT) is effectively treated with slow pathway (SP) ablation, often located in the right inferior extension (RIE) of the atrioventricular node, traditionally identified by anatomical landmarks and electrogram (EGM) characteristics. Based on conventional mapping studies, late SP activation occurs due to conduction block at the level of the tendon of Todaro (toT). The role of Three-dimensional (3D) electroanatomical (EA) mapping in identifying this activation and in guiding SP ablation is poorly understood. Purpose To assess whether EA activation mapping of Koch’s triangle provides more accurate RIE activation and SP localization, reducing radiofrequency (RF) delivery and recurrences without compromising procedural duration, success or safety, compared to a traditional EGM characteristics approach. Methods We retrospectively analyzed patients undergoing first ablation for typical AVNRT between April 2023 and July 2025. Patients were divided into an anatomically guided group (MAP0) and an EA activation mapping group (MAP1). Activation mapping of Koch’s triangle was performed in sinus rhythm and during right ventricular apex pacing using a 4-mm irrigated-tip catheter. Local activation time was annotated to the latest near-field component of the bipolar EGM; 8-isochronal late activation mapping was used to evaluate slowing/block at the level of toT. Conventional mapping used RF ablation (25–30W) at a site showing SP potentials in the RIE until junctional rhythm occurred. In MAP1, RF was delivered at the site of slowing activation in RIE (transition from 7th to 8th isochrone). Procedural time, RF deliveries, fluoroscopy time, complications, and recurrences were recorded over a 13-month median follow-up. Results 62 consecutive patients (mean age 52.7±16 years; 60% female) were recruited: 35 MAP0 and 27 MAP1. Acute success was achieved in 100% of cases. EA mapping significantly reduced procedural time [66 min (IQR 54.5–75.5) vs 87 min (IQR 60–106.5); p=0.007] with similar fluoroscopy exposure. Isochronal crowding and activation slowing in RIE were observed in all MAP1 cases. Median RF applications tended to be fewer in MAP1 (5 vs 7; p=0.19). RF was applied at a median distance of 11.7 mm (IQR 10.3–14.3) from the His potential and 10.4±4.5 mm from the fast pathway, confirming safety. 2 complications (3.2%) occurred - one transient PR prolongation requiring cryomapping in MAP0 - with no permanent AV block. 3 recurrences (4.8%), all in MAP0, were observed (p=0.25). No independent predictors of recurrence were identified. Conclusions EA activation mapping-guided ablation of the slow pathway within Koch’s triangle is safe, effective, and more efficient than conventional anatomical guidance, reducing procedural duration and showing a trend towards fewer RF applications and lower recurrence. This supports EA activation mapping as a valuable integration for precise and durable AVNRT ablation.MethodsResults