Noncontact three-dimensional mapping guides catheter ablation of difficult atrioventricular nodal reentrant tachycardia Pi-Chang Lee b , Ching-Tai Tai a , Yenn-Jiang Lin a , Tu-Ying Liu a , Bien-Hsien Huang a , Satoshi Higa a , Yoga Yuniadi a , Kun-Tai Lee a , Betau Hwang b , Shih-Ann Chen a, ⁎ a Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan b Department of Pediatrics, Taipei Veterans General Hospital and National Yang-Ming University, Taipei, Taiwan Received 26 January 2006; received in revised form 24 May 2006; accepted 10 August 2006 Available online 4 October 2006 Abstract Background: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common supraventricular tachycardia in adulthood. Although selective ablation of the slow AV nodal pathway can cure AVNRT, accidental AV block may occur. The details on the electrophysiologic characteristics, quantitative data on the voltage inside Koch's triangle, and the use of three-dimensional noncontact mapping to facilitate the catheter ablation of AVNRTassociated with a high-risk for AV block or other arrhythmias have been limited. Methods and results: Nine patients (M/F = 5/4, 34 ± 23 years, range 17–76) with clinically documented AVNRT were included. All patients had undergone previous sessions for slow AV nodal pathway ablation but they had failed, because of repetitive episodes of complete AV block during the RF energy applications. Further, one patient had a complex anatomy and 4 patients were associated with other tachycardias, respectively. The electrophysiologic studies revealed that 4 patients had the slow–fast, 4 the slow–intermediate and one the fast–intermediate form of AVNRT. Noncontact mapping demonstrated two types of antegrade AV nodal conduction, markedly differing sites of the earliest atrial activation during retrograde VA conduction, and a lower range of voltage within Koch's triangle. The lowest border of the retrograde conduction region was defined on the map, and the application of the RF energy was delivered below that border to prevent the occurrence of AV block. The distance between the successful ablation lesions and the lowest border of the retrograde conduction region was significantly shorter in the patients with the slow–intermediate form of AVNRT than in those with the slow–fast form (5.5 ± 3.4 vs. 15 ± 7.6 mm; p b 0.05). After the ablation procedure, either rapid pacing or extrastimulation could not induce any tachycardia, and there was no recurrence during the follow- up (10.3 ± 5.4, 2 to 22 months). Conclusions: Noncontact mapping could effectively demonstrate the antegrade and retrograde atrionodal conduction patterns, electrophysiologic characteristics of Koch's triangle, and guide the successful catheter ablation in difficult AVNRT cases. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Atrioventricular nodal reentrant tachycardia; Catheter ablation; Noncontact three-dimensional mapping system Atrioventricular nodal reentrant tachycardia (AVNRT) is well known to be the most common supraventricular tachycardia in adulthood. Although selective ablation of the slow AV nodal pathway can cure AVNRT [1], an accidental injury to the AV nodal tissue may happen during the radiofrequency ablation procedure. The information from three-dimensional noncontact mapping used to facilitate the catheter ablation of AVNRT associated with a high-risk for AV block or other arrhythmias has been limited. Further, the details of the electrophysiologic characteristics and quanti- tative data of the voltage inside Koch's triangle are limited. The purpose of this study was to 1) utilize noncontact three- dimensional mapping to define the antegrade and retrograde AV nodal conduction, 2) delineate the geometry of Koch's triangle and assess the electrophysiologic characteristics inside and outside Koch's triangle, and 3) guide the success- ful ablation of difficult AVNRT cases. International Journal of Cardiology 118 (2007) 154 – 163 www.elsevier.com/locate/ijcard ⁎ Corresponding author. Tel.: +886 2 2875 7156; fax: +886 2 2873 5656. E-mail address: epsachen@ms41.hinet.net (S.-A. Chen). 0167-5273/$ - see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2006.08.003