INTRODUCTION

Epicardial mapping and ablation is an important tool in the armamentarium of invasive electrophysiologists. Described in detail in previous chapters, this strategy relies on the insertion of a needle into a “virtual space” between the parietal and visceral pericardium. Unfortunately, adhesions may limit access and impede mapping in this space. Adhesions are most commonly encountered after cardiac surgery; however, they have been noted in the setting of prior percutaneous pericardial intervention, pericarditis (including that related to prior endocardial ablation), and even without an identifiable cause.

Prior work has suggested that abnormal electrograms requiring ablation can be found in the epicardial space in almost one-third of patients with ischemic cardiomyopathy.¹ This finding suggests that the need for epicardial mapping in patients with prior bypass surgery may be higher than previously appreciated, as approximately 30% of patients with ventricular tachycardia (VT) related to coronary artery disease have had prior coronary artery bypass surgery.² The need for repeat percutaneous epicardial procedures after an initial epicardial ablation procedure is another scenario that may present challenges with epicardial mapping. The frequency of this clinical scenario likely will depend on the center performing these procedures. A recent report from the UCLA Cardiac Arrhythmia Center reported on the need for repeat pericardial access after an initial VT ablation procedure with epicardial access in 26 of 155 procedures performed between 2004 and 2016.³ Adhesions noted at the time of the repeat procedure were relatively infrequent, with only three of the 23 patients undergoing a repeat percutaneous pericardial access procedure having adhesions. Interestingly, all three patients received intrapericardial steroids during the index procedure. There was no clear association between the time from the index procedure nor the duration and location of ablation and the subsequent development of adhesions, though the small number of patients with adhesions likely limited any meaningful evaluation of factors associated with the development of adhesions after an index pericardial procedure.

In this chapter, we will describe our approach to obtaining percutaneous epicardial access and mapping/ ablation in patients who have may have pericardial adhesions. In this situation, three options exist for epicardial mapping and ablation: (1) limited epicardial mapping via the coronary venous system, (2) percutaneous access, and (3) surgical epicardial access. We will limit our discussions to the former two, as the latter will be discussed in a later chapter.

LIMITED EPICARDIAL MAPPING FROM THE CORONARY VENOUS SYSTEM

In select patients with suspected pericardial adhesions, mapping the coronary venous system may be beneficial given the epicardial nature of this structure. Obel et al.⁴ reported on the utility of this approach for the ablation of idiopathic outflow tract VTs and Doppalapudi et al.⁵ reported on the utility of this approach for the ablation of idiopathic VTs originating from the crux of the heart. While potentially valuable, this approach has significant limitations, including partial access to the left ventricle based on individual variation in the coronary sinus anatomy (Figure 9.1). Moreover, even when a target is located, potential complications of ablation such venous stenosis, rupture, thrombosis, or collateral injury to an adjacent coronary artery may limit the use of this approach. Reduction of radiofrequency power applications (to 20–25 watts) during ablation may improve the safety of ablation with this approach. While this approach does allow one to undertake limited epicardial mapping when all else fails, in many patients, the region of interest is not accessible with coronary venous system mapping, particularly in scar-related VT. In these circumstances, access to the pericardial space is necessary.

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