Narrow QRS Ectopy with Concealed Connections from a Para‐hisian Origin to the Proximal Left Fascicles

INTRODUCTION:Catheter ablation of ectopy originating from the vicinity of the His bundle can be challenging.METHODS AND RESULTS:We report a case of a 33-year-old man with narrow QRS ectopy with preferential conduction from a para-Hisian origin to the proximal left fascicles, which was successfully eliminated by radiofrequency ablation in the right coronary cusp, guided by ultrahigh-resolution mapping of the His bundle, bundle branch, and fascicular electrograms.CONCLUSION:Some narrow QRS ectopy may originate from the vicinity of the conduction system, instead of the "true" conduction system, and have concealed connections from its origin to the conduction system.