A 57-year-old woman with a right-sided accessory pathway (AP) presented with frequent palpitations and underwent radiofrequency (RF) catheter ablation. Transthoracic echocardiography showed no structural heart disease, including Ebstein’s anomaly. A three-dimensional electroanatomical mapping system was used to map the ventricular and atrial activation during sinus rhythm and right ventricular (RV) pacing. The AP had no decremental property, and the earliest atrial activation site was located at 9 o’clock to the tricuspid annulus (TA). A SOUNDSTAR® catheter (Biosense Webster, Diamond Bar, CA, USA) revealed a strand-like structure connecting the lateral TA and anterior papillary muscle (white arrowheads in the Figure, Supplementary material online, Video). When mapping was conducted using a NAVISTAR® THERMOCOOL® catheter (Biosense Webster, Diamond Bar, CA, USA) along this structure, an AP potential was recorded at the Halo 7-8, MAP 3-4, and MAP 1-2 electrodes (dotted white arrow in the Figure) during sinus rhythm. A QS pattern was observed in unipolar recordings from MAP 1 and 2. The earliest atrial activation during RV pacing was located at the atrial end of a strand-like structure. Application of an RF current at the atrial end immediately abolished AP conduction. These findings suggested a strand-like structure containing an AP. The strand-like structure was observed during intracardiac echocardiography, but not during transthoracic echocardiography.
The full-length version of this report can be viewed at: https://www.escardio.org/Education/E-Learning/Clinical-cases/Electrophysiology.
Supplementary material is available at Europace online.
