INTRODUCTION

Epicardial ablation is an important treatment option for controlling ventricular tachycardia (VT), not only in structural heart disease, but also in idiopathic VT or channelopathy-related substrates. The requirement for epicardial ablation depends on the etiology of the underlying heart disease: 14%–40% for ischemic cardiomyopathy and 23%–75% for nonischemic cardiomyopathy.^1–4

Recently, the epicardial arrhythmogenic substrate in Brugada syndrome cases has drawn attention,⁵ and epicardial ablation in this cohort has been reported to provide an improved mid-term arrhythmia-free rate (96.7%) compared to that with endocardial-only ablation (70%).⁶ Percutaneous subxiphoid puncture^7,8 is a safe and relatively simple method. However, it may be challenging in patients with severe pericardial adhesions caused by previous cardiac surgery, pericarditis, or the insertion of an epicardial patch for an implantable cardioverterdefibrillator (ICD). Furthermore, a previous history of cardiac tamponade or epicardial ablation⁹ can result in severe pericardial adhesion with the use of the percutaneous approach. Although the percutaneous approach can be attempted by experienced operators in patients with severe adhesions,^10–12 inferior access might be preferable to anterior access, as postsurgical adhesion is usually more severe at the anterior pericardium.¹³ Previous studies have reported poor success rates in this population.^14,15 Based on the fact that 12%–54% of VT ablation patients have had previous cardiac surgery,^14,16 difficulty in performing percutaneous pericardial puncture may not be rare. Furthermore, percutaneous puncture could also be unsuccessful in patients without previous surgery; this may be due to the size and shape of the thoracis, the position of the diaphragm or liver, a thick sternum, and uncontrollable respiration under mild conscious sedation. Ebrille et al. reported a very rare case involving a congenital partial absence of the pericardium as an example of a challenging scenario for percutaneous puncture.¹⁷ Also, if the ablation target is in close proximity to a coronary artery, a surgical approach with direct vision may be preferable. Table 10.1 depicts the conditions that potentially require a surgical window for epicardial ablation.

Kumar et al. reported a total of 67 patients with VTs refractory to multiple drugs and previous endocardial and percutaneous epicardial ablation.¹⁸ They performed subsequent ablation procedures using the following alternative approaches: (1) transcoronary ethanol ablation, (2) surgical pericardial window, or (3) open-heart surgical cryoablation. A surgical window was used in four patients without any complications, achieving complete success in three (75%) and partial success in one (25%) patient.

Table 10.1 Possible Conditions for a Surgical Pericardial Window

A surgical pericardial window allows exposure of the pericardial space and enables the catheter to be advanced into the pericardial space, either directly or through a sheath. Unlike open-heart surgical cryoablation, this procedure can be performed in the electrophysiological (EP) laboratory or hybrid operation room (OR). Two pericardial window approaches have been reported: a subxiphoid surgical window16 and a limited anterior thoracotomy.¹⁹

In this chapter, we describe the indications, the importance of preprocedural imaging studies, practical methods and tips, and the possible risks of these surgical approaches in comparison to those of the percutaneous approach.

PREPROCEDURAL PLANNING

The most important aspect of preprocedural planning is the decision of whether a percutaneous or surgical approach should be adopted. Imaging studies are helpful in predicting pericardial adhesion²⁰ and echocardiography can, to some extent, depict the area of adhesion by showing pericardial thickening. Cardiac computed tomography (CT) with electrocardiographically synchronized protocols can detect the location and severity of the pericardial thickening and calcification (defined as a pericardial thickness > 4 mm). Additionally, in patients with previous coronary artery bypass grafts (CABG), the location of the bypass graft should be depicted in order to prevent potential injury to the graft during the blunt adhesion lysis.

Cardiac magnetic resonance imaging (MRI) is another important imaging modality used to detect pericardial thickening.²¹ Similarly to CT, cardiac MRI enables visualization of the entire pericardium and also provides functional information such as a diastolic filling pattern, similar to an echocardiography. Cardiac MRI myocardial tagging sequences can provide information on pericardial-myocardial adhesion. Unchanged tag grids at the end-diastolic and end-systolic phases suggest pericardial adhesion.²² Cardiac MRI with late gadolinium enhancement (LGE) also provides important information on the VT substrate. The presence and location of the subepicardial scar zone detected by cardiac MRI-LGE helps to guide the surgical approach.

Although these imaging studies cannot provide a definitive answer for which methods are most likely to lead to successful or unsuccessful puncture, a surgical window should be prepared when severe adhesion is suspected.

CREATION OF THE SURGICAL WINDOW

There are two types of surgical epicardial access: subxiphoid surgical access and anterior thoracotomy.

Subxiphoid Surgical Access

Creation of a surgical window can be performed by a cardiac surgeon, either in the EP laboratory or ideally in the hybrid OR. The subxiphoid window was first reported in 2004 and is the most frequently selected approach.¹⁶

The subxiphoid window procedure details are as follows (Figure 10.1, Panels A and B). Under general anesthesia with endotracheal intubation, a 3-inch (10-cm) vertical incision is made at the subxiphoid area. The incision is extended through the subcutaneous tissue and then the linea alba. The pericardium is exposed and opened horizontally, parallel to the diaphragmatic reflection. The incision is then extended, and blunt dissection of the adhesion is performed to fully expose the diaphragmatic and posterior epicardium. An ablation catheter, or an 8- or 9-Fr sheath, can be inserted directly into the pericardial space. A sheath can either be inserted directly from the window or a guidewire can be introduced under direct visualization from the adjacent site into the pericardium; the sheath can then be inserted (Figure 10.1, Panel B) and the pericardial window can be temporarily closed. This method is thought to decrease the potential risk for infection and keep the cardiac surface temperature warm during the procedure. In the initial report, the target ablation sites were predominantly distributed at the inferior wall.¹⁶ Maury et al. reported that although the apical area was accessible through this approach,²³ the lateral region was only accessible in 33% of cases.²⁴ Adhesiolysis was achieved by careful catheter advancement into the space.

Limited Anterior Thoracotomy

Limited anterior thoracotomy allows access to the anterior and more basal areas. In the early reports of this approach, the procedure was performed in the OR.^14,23 Michowitz et al. reported a case series of this approach performed in the EP lab (Figure 10.2).¹⁹

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