**4.1 Traditional method (posterior approach)**

After obtaining informed consent, the procedure would be performed with the patients in a fasting state under general anesthesia. Pre-procedure subxiphoid echocardiography was recommended to perform routinely. In some cases, the echocardiography could help the operator avoid liver or gastric injuries. A subxiphoid puncture was performed to penetrate the pericardium in the inferior aspect of the hear according to the technique described by Sosa et al [2]. Access to the pericardium was achieved by using an 18 G Tuohy Needle (Arrow International, Inc., Reading, PA, USA) in the laboratory of Taipei Veterans General Hospital through the subxiphoid process. The anteroposterior projection was usually used to direct the access in the anterior/posterior plane, while the left anterior oblique (LAO) 60° projection was used to guide the needle leftward tangentially to the cardiac border. **Figure 5** demonstrated the adjacent structure with these two views by reconstruction of the CT. After passing through the diaphragm, 1-2 cm3 of contrast could be injected between the diaphragm and pericardium to observe tenting of the pericardium. After entering the posterior side of pericardium, a 0.032 guidewire would be advanced to the left heart border in the LAO projection, and 10 cm3 of contrast could be injected into the pericardial space through a 5F dilator or the side hole of a 5Fr sheath to allow for visualization of any adhesions. (**Figure 6**) An 8-Fr Sheath or flexible long Sheath would be exchanged by using the guide wire. The ablation/ mapping catheter would be inserted through the sheath after obtain the access to avoid injury by the edge of the sheath. Angiography would be performed while locating the catheter in the interested area to avoid coronary injury. (**Figure 7**) After the procedure, the epicardial sheath was exchanged for a pigtail. Pericardial injections of hydrocortisone 100 mg and ketorolac tromethamine 30 mg were routinely given immediately and 24 hours after the epicardial procedure to prevent any future epicardial adhesions or pericarditis.

#### **Figure 5.**

*The anatomy with anterior–posterior view (left panel) and LAO view (right panel). The green arrow indicated the anterior approach and the red arrow indicated the posterior approach.*

#### **Figure 6.**

*Epicardial puncture in a patient with arrhythmogenic right ventricular cardiomyopathy. The anterior– posterior view (left panel) and LAO view (right panel) showed the wire in the epicardial space surrounding the whole heart and the contrast in the epicardial space without adhesion.*
