AV Nodal Reentrant Tachycardia in a Patient with Persistent Left Superior Vena Cava: Distinction between AV Nodal Versus Atrial Reentry

A 75-year-old male presented with palpitation on exertion. He suffered from frequent tachycardia attacks. His 12-leads electrocardiogram showed irregular cycle lengths (400–550 ms) of tachycardia with occasional 2:1 atrioventricular conduction (thus AV reentry was excluded). He had a complex anatomy of persistent left superior vena cava (PLSVC)/ enlarged coronary sinus (CS). The activation map in a 3-dimensional CARTO system (Biosense-Webster, USA) was merged with the multi-detector computed tomography image and revealed that the tachycardia spread centrifugally from the junction between the PLSVC and enlarged CS. However, delivery of radio frequency (RF) energy to the earliest atrial activation site did not affect the tachycardia. Finally, the tachycardia was diagnosed as a fast/ slow type atrioventricular nodal reentrant tachycardia (AVNRT) because the tachycardia was cured only after the anterograde/retrograde AV conduction was disturbed by the application of RF energy to the posteroseptal perimitral area, possibly due to the injury to the AV node.