Abstract 9796: Atypical Right Atrial Flutter with Double Loop Reentry Involving the Cavotricuspid Isthmus and Superior Vena Cava with Successful Ablation

Abstract

Introduction: Atrial flutter (AFL) with figure-of-eight reentry (FOER) is effectively terminated by catheter ablation (CA) of the shared isthmus. Case: A 50-year-old man with prior mitral valve (MV) repair presented to our hospital with palpitations for 9 months refractory to metoprolol. ECG showed coarse atrial fibrillation at 61 bpm. Echocardiography showed left ventricular LVEF of 45%. Electrophysiology study revealed AFL (cycle length, TCL 290 msec) with a concentric activation pattern on the coronary sinus (CS) catheter, and a chevron pattern on the Halo catheter placed against the lateral tricuspid annulus (TA). Entrainment map revealed a near equal post-pacing interval and TCL in proximal CS, low lateral right atrium (RA), and CTI. Incomplete line of block was noted in the anterior wall of RA near the superior vena cava (SVC), likely from prior atriotomy scar. Double loop reentry (DLR) was demonstrated with one wavefront (WV) traveling counterclockwise around the TA using the CTI, and the other WV traveling posteriorly around the SVC (Figure). After CTI ablation, TCL changed from 290 msec to 330 msec suggesting blocked CTI. Now, the WV was a single loop around the SVC, confirmed by repeat activation mapping. Linear ablation from anterior TA to the anterior aspect of the SVC terminated the AFL. Differential pacing from either side of the anterior line and the CTI demonstrated a conduction time of > 200 msec and 150 msec in either direction, respectively. Decremental atrial pacing was unable to induce any arrhythmias. Discussion: FOER in this case is suggested by fusion of WVs in the lateral RA. The 2 circuits each had their own conduction gap, in the CTI and anterior RA wall near the SVC, respectively. DLR was proven by entrainment as well as activation mapping. The faster CTI-dependent AFL was entraining the upper loop reentry circuit. Conclusion: Atypical right AFL with DLR mimicking FOER was successfully terminated by CA of CTI and anterior line of ablation from TA to SVC.