Extracardiac ice formation during CoolLoop cryoablation of atrial fibrillation

A 75‐year‐old male patient was referred for longstanding atrial fibrillation ablation. We performed this procedure combining an epicardial and endocardial approach. Under general anesthesia and via a left‐sided thoracoscopic approach, we isolated the pulmonary veins (PVs) and the roofline and inferior line were created using a radiofrequency tool. To isolate the endocardial PVs, a transseptal puncture was performed via the groin, and a cryoablation CoolLoop catheter (AFreeze GmbH, Innsbruck, Austria) was advanced into the left atrium. Ice crystals started to appear on the epicardial surface of the left inferior PV antrum after 121 seconds later, those crystals had formed an ice plaque. For the first time in humans, we were able to visualize the transmural effects of cryothermal energy ablation via a CoolLoop catheter on the epicardial surface of the ostium of the PV.