Introduction: Sinus tachycardia with perpetuating slow pathway conduction may mimic narrow QRS short RP tachycardia and cause symptoms.
Case: An 81-year-old man complained of palpitation because of narrow QRS short RP tachycardia (CL 550ms) was referred for EPS/ablation. The ECG during sinus rhythm showed normal PQ interval and narrow QRS complex. During EPS study, his AH and HV intervals were 132ms and 57ms, respectively. RV pacing showed no VA conduction. Programmed atrial stimulation revealed dual-AV node physiology. No tachycardia was inducible without isoproterenol. However, after intravenous administration of isoproterenol, two ventricular responses (1:2 AV conduction pattern) were occurred spontaneously and induced by rapid atrial stimulation. The first AH interval was 77 ms and that second was 645ms. After the two ventricular responses, sinus tachycardia with perpetuating slow pathway conduction (AH 360ms) mimicked short RP tachycardia. Single atrial extra-stimulation just before His potential advanced the next His potential and atrial tachycardia with fast pathway conduction was resumed (peel back phenomenon).
Conclusions: We report a rare case of sinus tachycardia with perpetuating slow pathway conduction mimicked narrow QRS short RP tachycardia.