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).