Commentary:
With the given clinical background atypical AVNRT was the most likely possibility. But maneuvers were needed to prove or exclude other diagnoses. Para his pacing (PHP) in sinus rhythm was suggestive nodal route for VA conduction. His-refractory PVC didn’t perturb the tachycardia circuit. Junctional tachycardia (JT) was ruled out as single late atrial premature depolarization (APD) could reproducibly terminate tachy2. VOP repeatedly terminated tachycardia. VOP could not entrain the SVT/atrium (even for a single beat), even after 7-8 beats before termination, hence, ruling out AVRT. VOP repeatedly terminated the tachy2 without conduction to A (third beat in Fig2C), thus, ruling out AT. With AVNRT as the only diagnosis of exclusion, further slow pathway modification was performed. Tachy2 became non-inducible afterwards. No jump or AV echo was produced at baseline. With isoprenaline, single typical AV nodal echo beat noted (with PR of 360ms).