The inferior displacement of the His bundle and fast pathway in a patient with common type atrioventricular nodal tachycardia: Three-dimensional computed tomography analysis

Abstract

A 66-year-old woman with palpitations was referred to our center for catheter ablation due to drug-refractory, common type atrioventricular nodal tachycardia (AVNRT). A selective slow pathway ablation was attempted. A fast junctional rhythm with transient ventriculoatrial block followed by transient prolongation of the A-H interval occurred immediately after the radiofrequency (RF) application at the coronary sinus ostium (CSOS) level. To assess the location of the fast pathway and His bundle, we sought to visualize the anatomy of the triangle of Koch (TOK) by three-dimensional computed tomography (CT).

Keywords: AVNRT; Catheter ablation; Computed tomography; Fast pathway; His bundle.

Fig. 1

A: Activation map of the His potential in the TOK using the NavX system. The His potential is annotated at each site (the right panel). The endoscopic view in the RAO direction. The white arrowheads indicate the tendon of Todaro. The small 3D green tags indicate the His potential recording sites, which were recorded by the His catheter. The small yellow tag indicates the maximum His potential recording site. The normal 3D yellow tags indicate the dislocated His potential recording sites, which were recorded by the ablation catheter. The 3D red and white tags indicate the unsuccessful ablation sites with or without ventriculoatrial block, respectively. The 3D blue tag indicates the successful ablation site. NavX demonstrated the activation of the His potential. The successful ablation site was located at a ventricular site, where a small atrial electrogram was recorded (the bottom panel). B: St-His interval map of the TOK using the NavX system. The St-His interval at the middle portion of the superior portion of the TOK were 56 ms and 96 ms, respectively.

Fig. 2

The three-dimensional reconstructed true anatomy of the TOK and surrounding organs. The red arrowheads indicate the tendon of Todaro. The green object indicates the membranous septum. The red arrow indicates the atrioventricular node in the majority of patients. The dotted yellow line indicates the bottom of the membranous septum. TOK=triangle of Koch, CSOS=coronary sinus ostium.