Thromboembolic complications after the ablation procedure have several possible causes. These include thrombus formation on or within the stationary sheaths, endothelial lesions from the procedure, systemic activation of platelets and of the coagulation system, transseptal puncture with a persistent atrial septal defect, periprocedural cardioversion, and local heating during energy delivery causing thrombus formation on the catheter tip or at the ablation site. Air emboli occurring during the transseptal catheter exchange or disruption of thrombi in the atrium before the procedure may also result in thromboembolic events.