Abstract 15782: A Rare Case of Septal Atrial Flutter

Abstract

Background: Isthmus-dependent counterclockwise or clockwise flutter is well defined and responsive to radiofrequency ablation (RFA) of the cavotricuspidisthmus (CTI). However, inter-atrial septal (IAS) flutter is rare and occurs with IAS substrate abnormalities and prior cardiac surgery. Case: A 62-year-old female with paroxysmal AF on rivaroxaban, hypertension and diabetes mellitus presented with palpitations refractory to propafenone and metoprolol. She underwent successful isolation of all four pulmonary veins (PVs) and RFA of the CTI with demonstration of bidirectional block. A year later, she presented with atypical AFL (Fig 1A) failing cardioversion. During redo ablation, bipolar voltage map of the left atrium (LA) demonstrated durable isolation of all four PVs. Burst pacing (BP) from the coronary sinus (CS) up to 220ms did not induce AFL. The LA posterior box was isolated by creating a roof line and a line connecting the inferior veins (Fig 1B). No extra-PV triggers were noted on high dose isoproterenol. However, during the washout period, BP from the CS induced AFL with a tachycardia cycle length of 237ms, concentric CS activation and almost simultaneous activation along the crista in the right atrium (RA). High-density activation and coherent mapping of LA and RA suggested a micro-reentrant circuit over the posterior IAS with wavefront collision across the CTI (Fig 1C, D). Concealed entrainment was observed over the LA posterior septum near the transseptal puncture site. RFA successfully terminated the AFL. RFA was performed in a sequential unipolar fashion on both sides of the septum over areas of fractionation. No atrial arrhythmias were inducible with BP on or off isoproterenol. Patient remained in sinus rhythm at 9 month follow up. Conclusion: IAS flutter post AF ablation or cardiac surgery is rare, and management is challenging. While RFA has a 93% success rate, larger studies are required to further delineate this condition.