LAUSR

When a patient who has undergone successful slow pathway ablation for typical AVNRT with elimination of symptoms develops a recurrent long Introduction Atrioventricular nodal reentrant tachycardia (AVNRT) is the most commonly diagnosed supraventricular tachycardia (SVT) in the electrophysiology (EP) lab in patients with recurrent sustained paroxysmal SVT. The ablation target for both typical (slow-fast) and atypical (fast-slow) AVNRT is usually the right inferior extension of the slow pathway (SP), found between the middle coronary sinus ostium and the tricuspid annulus along the posterior inferior right atrium. Success rates for first-time radiofrequency (RF) ablation have been reported as high as 95%–98%. Two patients are presented here who underwent successful SP modification for typical AVNRT without clinical recurrence, who presented years later with atypical AVNRT. RP tachycardia several years later, the diagnosis of atypical fast-slow AVNRT must still be considered. Case report Case 1 A 58-year-old woman with a medical history of Crohn disease, psoriatic arthritis, and a prior diagnosis of typical AVNRT underwent successful catheter ablation at an outside institution 12 years prior to presentation. Before her ablation 12 years ago, she had monthly to weekly episodes of tachycardia over the previous few years. Ablation of the SP was reportedly successful with a single RF lesion. She had complete resolution of her symptoms for 12 years until 2 months prior to presentation, when she began to have frequent, daily episodes of palpitations. Rhythm strips recorded during symptoms showed a long RP tachycardia initially thought to be atrial tachycardia. An EP study was performed. At baseline, there was evidence of dual AV nodal physiology with a demonstrable A-H “jump” during delivery of incremental atrial extrastimuli. A mid RP tachycardia was easily induc-