Atrial Tachyarrhythmias Concomitant with Perimitral Atrial Flutter during Catheter Ablation

Background: We report 3 cases demonstrating transition from perimitral atrial flutter to a different atrial tachycardia/flutter (AT/AFL) during linear ablation between the left pulmonary vein (PV) and the mitral annulus (mitral isthmus ablation). Methods: N/A. Results: A 67-year-old man with prior pulmonary vein isolation (PVI) underwent RFCA for recurrent AFL. Electrophysiological study (EPS) initially revealed clockwise perimitral AFL. During mitral isthmus ablation, the AFL changed into a focal AT from left atrial (LA) inferior wall with change in cycle length (CL) from 230 ms to 310 ms, which was successfully ablated at the earliest atrial activation site. A 70-year-old woman with prior mitral valve replacement and atrial fibrillation (AF) underwent RFCA for persistent AFL. EPS revealed clockwise perimitral AFL (CL=270 ms). During mitral isthmus ablation, the AFL changed into common AFL without change in CL, thus the two AFLs formed a dual-loop reentry circuit over both atria. A 65-year-old woman with prior PVI underwent RFCA for recurrent AFL. EPS revealed counterclockwise perimitral AFL. During mitral isthmus ablation, the AFL changed into a LA roof dependent AFL with change in CL from 205 ms to 250 ms, which was successfully terminated by LA roof linear ablation. Conclusion: Perimitral AFL can occur simultaneously with another AT/AFL, which becomes apparent with termination of perimitral AFL.