Transient ST-segment elevation due to coronary slow flow during cryoballoon application

This report is a description of a rare case of transient ST-segment elevation during cryoballoon application for paroxysmal atrial fibrillation (PAF). A 74-year-old male with symptomatic PAF was referred to the center for ablation. During cryoablation of the left superior pulmonary vein (188 seconds, -48°C), ST-segment elevation in the anterolateral leads was observed suddenly, though without any significant complaint. Upon the increase in the ST segment, the cryoapplication was immediately terminated. Coronary artery angiography was performed less than 5 minutes after balloon deflation and demonstrated coronary slow flow with a corrected Thrombolysis In Myocardial Infarction (TIMI) frame count of 48.4 (normal range: 21±3) in the left anterior descending artery (LAD). There was no significant flow-limiting lesion, coronary vasospasm, thromboembolus, or air embolus in any coronary vessel. The TIMI frame count for the right coronary artery and the circumflex artery was normal. The ST-segment elevation gradually returned to the baseline in 14 minutes without any intervention. A control TIMI frame count of the LAD was 22. A decision was made not to repeat the cryoapplication in this vein because there was both an entrance and an exit block. The other 3 pulmonary veins were then isolated uneventfully. The patient was discharged from the hospital the next day without symptoms or unusual electrocardiogram activity.