The proximity to vascular structures is a limiting factor during radiofrequency ablation.¹ Major atrial coronary arteries, including the sinoatrial node artery (SNA), were commonly found in or crossing the areas involved in left-sided atrial ablations with significant caliber.²

A 52-year-old woman with a previous mitral valve replacement was referred for atrial tachycardia ablation. She underwent an electrophysiological study, which revealed a perimitral clockwise flutter. We decided to perform an anteroseptal mitral isthmus line between the right superior pulmonary vein and the septal mitral annulus (Figure 1). However, suddenly, asystole developed during the ablation procedure. Coronary angiography was performed due to suspicion of possible injury to the SNA; angiography demonstrated the subtotal acute occlusion of the SNA originated unusually from the left circumflex artery fluoroscopically close to the successful ablation site (Figure 2). Energy delivery was immediately terminated, but asystole persisted for 11 seconds followed by sinus bradycardia. SNA flow was significantly slow at the termination site and was graded as Thrombolysis In Myocardial Infarction (TIMI) flow grade 0–1 (Video 1). We could not cross the lesion by 0.014 floppy wire due to the sharp angle (Video 2). However, 10 minutes later, after a 200 μg intracoronary nitroglycerine injection, the flow was restored to TIMI flow grade 2 (Video 3). Therefore, the asystole was self-healing, and no complications were seen in the following follow-up. Acute or sub-acute sinus node dysfunction has only recently been suggested as a potential complication of mitral anteroseptal line or cardioneuroablation.³⁴ Furthermore, asystolic pauses have been observed during RF ablation of left ventricular free-wall accessory pathways, slow AV node pathways, and the left superior pulmonary vein.⁵⁶⁷ It should be kept in mind, in particular, during ablations of left-sided atrial tachyarrhythmias.

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