Epicardial Radiofrequency Ablation: Who, When, and How?

*Chin-Yu Lin*

## **Abstract**

In the past decades, it has been known that reentry circuits for ventricular tachycardia or focal triggers of premature ventricular complexes are not limited to the subendocardial myocardium. Rather, intramural or subepicardial substrates may also give rise to ventricular tachycardia, particularly in those with non-ischemic cardiomyopathy. Besides, some of the idiopathic ventricular tachycardia might be originated from epicardial foci. Percutaneous epicardial mapping and ablation have been successfully introduced to treat this sub-epicardiac ventricular tachycardia. Herein, this chapter reviews the indications for epicardial ablation and the identification of epicardial ventricular tachycardia by disease entity, electrocardiography and imaging modalities. This chapter also described the optimal technique for epicardial access and the potential complication.

**Keywords:** epicardial, ventricular tachycardia, ablation, non-ischemic cardiomyopathy, idiopathic

## **1. Introduction**

The pericardium is a two-layer membrane surrounding the heart and vital vessels. The two-layer structure included a serous visceral membrane inside and a fibrous membrane (parietal pericardium) outside. The fibrous membrane is adhered to the diaphragm, posterior part of sternum by the tissue and ligament to fix the heart. The pericardium encloses the heart and pericardial fluid, which provides lubrication for the myocardium [1]. Pericardial puncture is a standard and useful therapeutic procedure for the treatment of diagnosis of tamponade or symptomatic pericardial effusion [1]. In 1996, Sosa et al. first described the use of pericardial puncture in an electrophysiological laboratory for epicardial ablation in ventricular arrhythmia, [2] the use of pericardial puncture to map and ablate ventricular arrhythmia started to expand in other diseases [3].

Before to the era of catheter ablation with epicardial approach, patients with ventricular tachycardia (VT) refractory to catheter ablation from the endocardium often required surgical approach. The technique became well-developed and skilled in high-volume center recently. Many centers reported the successful application of the epicedial ablation in a diverse range of cardiac arrhythmia. Therefore, the indication for the epicardial approach has extended. The potential indication included substrate/ idiopathic VTs, accessory pathways, and miscellaneous supraventricular tachycardias [4]. Since Sosa et al. first introduced the application of epicardial ablation for the ventricular arrhythmias (VAs) in Chagas disease, [2] the use of this technique through a percutaneous method has been applied to other diseases [3].

In the patients with ischemic cardiomyopathy due to prior myocardial infarction (MI) and VT, the involved circuit mostly involved the inner part of the heart [5]. In the previous report, part of the ischemic VT circuit may involve areas within the subepicardial area [6]. The advantage of the epicardial approach was demonstrated by clinical study. An approach with combined endo-epicardial mapping/ablation has been reported to show a better outcome selected patients with non-ischemic cardiomyopathy (NICM) VT ischemic VT [7–10]. Furthermore, the percutaneous technique for epicardial access have been proven to improve outcomes with an acceptable risk of peri-operative adverse event in experienced operator or high-volume centers [11]. However, there were many surrounding epicardial vascular structures or nerves in the tract of epicardial puncture. The unskilled operators may encounter serious and detrimental complications. Prior studies have reported the incidence rate of major complications around 4.1-8.8%, including adverse event of a hemopericardium, intra-abdominal bleeding, and arterial/venous/nerve injuries [11–14]. This chapter was aimed to discuss the clinical implication, patient selection, and detailed procedure for the epicardial ablation in the patients with VA.
