The cryoballoon is introduced via a 12 transseptal sheath and over-the-guidewire to the base of the left atrial appendage and is inflated manually. Injection of contrast medium over the transseptal sheath demonstrates complete basal occlusion of the left atrial appendage. Note that the guidewire leaves via the distal left atrial appendage into the pericardium. CB, cryoballoon; CS, coronary sinus; GW, guidewire; TS, transseptal sheath.