Thrombus formation is a complication that can occur with any ablation technique. Thrombi may dislodge and embolize, causing a stroke, myocardial infarction or other ischemic event. Therefore, it is required that activated clotting time (ACT) is kept above 300 seconds. This should be monitored every 30 minutes, and heparin should be administered depending on the outcome. The operator is responsible for maintaining an adequate ACT.