Excerpt

A 35-year-old man with recurrent episodes of paroxysmal supraventricular tachycardia was referred to our hospital for an electrophysiological (EP) study and catheter ablation. An ECG at rest revealed a short PR interval and a delta wave consistent with Wolf–Parkinson–White (WPW) syndrome involving a septal accessory pathway. After obtaining written informed consent, an EP study was performed. Electrode catheters were positioned on the right atrial appendage, the His bundle–right ventricle (RV) apex, and the coronary sinus (CS) using a halo catheter that also covered the tricuspid annulus. At baseline, the sinus cycle length, atrial-His (AH) interval, and His-ventricular (HV) interval were 790, 90, and 25 ms, respectively. Programmed electrical stimulation from the RV and right atrium (RA) induced narrow QRS tachycardia with a cycle length of 360 ms without sudden prolongation of the ventriculoatrial (VA) or AH interval. The atrial activation sequence during tachycardia was identical to that produced by constant ventricular pacing during sinus rhythm. Single ventricular stimulation applied during tachycardia when the His bundle was refractory advanced the atrial activation. This tachycardia was diagnosed as orthodromic atrioventricular reciprocating tachycardia using a posteroseptal accessory pathway. The accessory pathway was successfully eliminated by radiofrequency application. …