Para-Hisian pacing in a patient with a long RP tachycardia-What is the mechanism?

Abstract

A 29-year-old man underwent a diagnostic electrophysiology study because of a recurrent symptomatic long RP supraventricular tachycardia (SVT). Twelve-lead electrocardiography and echocardiography were normal. Atrio-His (AH) and His-ventricular intervals measured 86 and 52 ms, respectively. The patient had retrograde ventriculoatrial (VA) activation that was midline and decremental. Para-Hisian pacing repeatedly induced his clinical SVT (Figure 1, top). The response to His-refractory ventricular premature depolarizations and entrainment from the ventricle are shown (Figure 1, middle and bottom).