Nodoventricular Orthodromic Re-Entrant Tachycardia Mimicking Slow/Fast Atrioventricular Nodal Re-Entrant Tachycardia

BACKGROUND: Concealed nodoventricular orthodromic re-entrant tachycardia (NV-ORT) is an extremely rare form of paroxysmal supraventricular tachycardia that can mimic the electrophysiologic characteristics of slow/fast atrioventricular nodal re-entrant tachycardia (AVNRT). CASE SUMMARY: A 65-year-old woman presenting with narrow QRS tachycardia underwent an electrophysiologic study, which revealed dual atrioventricular nodal physiology and inducible wide QRS tachycardia with right bundle branch block triggered by catheter stimulation, accompanied by an atrio-His jump. Ventricular overdrive pacing demonstrated a ventricular-ventricular-atrial activation sequence, orthodromic His capture, and termination without atrial capture during the fusion period. The tachycardia was diagnosed as NV-ORT, and successful slow pathway ablation eliminated inducibility. DISCUSSION: NV-ORT closely resembles slow/fast atrioventricular nodal re-entrant tachycardia, but diagnosis can be challenging when ventriculoatrial conduction block is absent or retrograde conduction occurs via the fast pathway. TAKE-HOME MESSAGE: Recognition of NV-ORT requires careful analysis of pacing responses and His potentials.