**5. Periprocedural complications of an epicardial approach**

In the prior report, the incidence of major complications was 10.0%, and that for minor complications was 17.5% [14]. Prior single and multicenter studies also reported similar findings [11, 12]. However, it is important to keep in mind that these complication rates were obtained from arrhythmia centers with an experience of epicardial approach. The surgical backup was required for potential major complications. Major complications of intra-abdominal bleeding due to vessel damage and MI owing to ablation in the adjacent area were reported [68]. Another possible cause of intra-abdominal bleeding is the liver puncture or perforation. The operator should also take care for the location of the coronary sinus. Coronary sinus puncture might occur if the puncture site is close to the base of the heart. Thus, detailed preoperative evaluations by ECG, echocardiography, and peri-operative image, especially for patients with hepatomegaly or a congested liver, may prevent the occurrence of any life-threatening complications.

RV puncture was not uncommon and it has been reported to be a minor complication with an incidence of 4. 5 ~ 7. 5% [13, 14, 68]. The RV puncture could be reduced after a learning curve. Post-procedural pericarditis was common. Prolonged and intolerable chest pain due to pericarditis might be improved by the administration of intrapericardial steroids and non-steroidal anti-inflammatory drugs. Phrenic nerve injuries and coronary artery damage could be avoided by phrenic nerve pacing and pre-ablation angiography [69, 70].

#### **5.1 Patients with anticoagulant**

In the patient with anticoagulant, the epicardial access could be performed according to the guideline. After excluding the potential risk of adhesion, history of epicardial surgery, and complex anatomy, the procedure might be classified as a minor risk procedure in an experienced operator [71]. Therefore, the procedure could be performed at NOAC through level (12 or 24 hours after the first intake)

and resume after the procedure or latest next day without active bleeding. Beside, the procedure should be better performed by experienced operator and avoid repeated RV puncture. Antidote or blood transfusion should be available in the hospital.
