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The history of interventional therapy of arrhythmogenic ventricular scar to prevent recurrent ventricular tachycardia (VT) has its origins in the operating room. Resection of endocardial scar and aneurysms in the postinfarction setting were shown to significantly reduce arrhythmia recurrence in the 1980s.1,2 More importantly, surgical exposure allowed for direct validation of scar modification with alteration or elimination of abnormal, late, and fractionated local electrogram recordings within the region of scar resected.^3,4 These observations represent an important milestone in the timeline of VT ablation, where subsequent strategies with catheter ablation have sought to emulate and reproduce these operative approaches in a less invasive fashion.

Since the advent of electroanatomic mapping in the late 1990s,^5,6 subendocardial resection² and encircling ventriculotomy⁷ have been essentially replaced by endocardial catheter ablation via percutaneous approaches, obviating the attendant risks and morbidity of sternotomy and cardiopulmonary bypass. Percutaneous epicardial access, pioneered by Sosa et al. 20 years ago,⁸ has improved our understanding and ability to target scar involving the outer surface of the myocardium in patients with Chagas disease, arrhythmogenic right ventricular cardiomyopathy (ARVC), nonischemic cardiomyopathy (NICM), and ischemic cardiomyopathy (ICM), without the requirement of surgical access.^9–12

As VT ablation has evolved considerably over the past 30 years, surgical treatment of VT currently plays more of a niche role in a subgroup of highly selected patients with symptomatic arrhythmia refractory to standard approaches. In this chapter, we examine the indications and common clinical scenarios where a hybrid approach to surgical VT ablation has an important role in current practice, with attention to logistical setup and practical considerations.

Rationale and Indications

Epicardial mapping and ablation is indicated for patients who have a high likelihood of arrhythmogenic epicardial substrate,¹³ particularly those who have undergone prior unsuccessful or incomplete endocardial ablation.¹⁴ In this context, surgical hybrid access is typically performed when (1) a percutaneous approach is not feasible or impaired by the presence of pericardial adhesions or (2) epicardial ablation via subxiphoid percutaneous approach fails due to biophysical and/or anatomic limitations. Surgical ablation and exposure offers the operator the ability to access the pericardial space in a more controlled setting and allows for direct visualization of the epimyocardium in relation to adjacent structures.

Pericardial Adhesions

A sizable number of patients who require epicardial ablation have had previous cardiac surgery, mainly patients with ischemic CMP and previous coronary artery bypass graft surgery (CABG) (12 to 45% of patients with ischemic VT), but also patients with valvular heart disease.15,16 Two studies reported that the main reasons for failed epicardial access were previous cardiac surgery, pericarditis and epicardial defibrillator patches. Roberts-Thomson et al.¹⁷ achieved epicardial access in only 2 of 10 patients with previous cardiac surgery and Sacher et al.¹⁵ reported that in 15 of 16 patients with failed epicardial access one of the above situations could be reported.

On the other hand, the presence of pericardial adhesions may be viewed as only a relative contraindication, with significant practice variation across experienced centers. Sosa et al. initially described a series of five post cardiac surgery patients who underwent successful nonsurgical percutaneous subxiphoid access.¹⁸ However, mapping was limited to the inferolateral wall due to dense adhesions. Tschabrunn et al. reported successful epicardial access in 10 of 10 patients with previous noncoronary cardiac surgery or pericarditis.¹⁹ However, all patients had dense adhesions that were carefully dehisced by blunt catheter dissection. In 2 patients (20%) dense adhesions precluded access to the epicardial site of interest. Mulpuru et al. more recently demonstrated the feasibility of a percutaneous approach in postsurgical patients, including those status post coronary artery bypass grafting.²⁰ Consistent with prior experience, “adhesiolysis” is almost always necessary and incomplete exposure and mapping is the general rule.

The presence of pericardial adhesions makes it difficult for the operator to rely on tactile or visual feedback to signify entry into the pericardial space. Typically, the wire meets resistance and additional antegrade movements of the needle may increase the risk of right ventricular (RV) puncture. Thus, surgical backup should be available in all cases where percutaneous epicardial access is performed, as localized or generalized tamponade may ensue due to the coronary vessel or right ventricular puncture or laceration. A useful method to identify entry into the pericardial space in the setting of adhesions is to place a soft 5F dilator into the space accessed and perform a contrast pericardiogram.¹⁰ The characteristic appearance of a concentrated, localized crescent pattern confirms entry into an adhesed space (Figure 54.1). The contrast may be helpful when performing adhesiolysis, as the outer margins expand with the wire or catheter used to gently create more space. A steerable sheath is very useful but may increase the risk for injury or bleeding. Fluoroscopically, the appearance of the pericardial tissue that is slowly being released from dense adhesions has the appearance of a “pseudo-colon.”

Adhesions can be particularly severe in the setting of prior pericarditis and particularly in patients with prior failed attempted access complicated by bleeding. These patients should be considered similarly to those with prior cardiac surgery. Recently, we reported a case of subepicardial dissection in a patient with NICM with dense adhesions in the absence of prior surgery.²¹ Significant bleeding developed as a result of gradual “blind” adhesiolysis using a steerable sheath and steerable linear diagnostic catheter and required surgical exploration with oversewing of the dissection. This case highlights the increased level of risk in such patients and illustrates the rationale behind our preference to proceed with a surgical approach in any patient with known or high likelihood of pericardial adhesions.

Failed Ablation Via Percutaneous Approach

The most common reasons for failure of epicardial ablation via a percutaneous approach is when the target site is either (1) too close to a major epicardial coronary artery or (2) insulated by significant epicardial fat that impairs effective radiofrequency (RF) energy delivery (Figure 54.2). In a study by van Huls van Taxis with registration with computed tomography imaging, fat thickness of >7 mm and proximity to coronary arteries were most commonly associated with failed epicardial ablation.²² Although a wide spectrum of epicardial sites of origin located on the basal LV along the mitral annulus may be successfully eliminated via the coronary venous system,^23,24 transvenous ablation may be still be limited by narrow/tapered lumen, high impedance, low energy delivery, and proximity to the proximal left coronary system. In these situations, a percutaneous approach has not been shown to have a high yield due to the same issues of epicardial fat and coronary artery proximity.^10,25

A surgical approach has the advantages of direct visualization of the target region with the ability to dissect epicardial fat and potentially shift away major epicardial arteries. As the catheter lies tangentially to the epicardium in a percutaneous approach, a safety margin of 5 mm²⁶ is typically violated during all phases of the cardiac cycle, whereas a perpendicular catheter approach has the potential to increase the stability of a catheter, reducing the risk for adjacent coronary artery injury.

In these difficult scenarios, the feasibility of surgical ablation in a separately staged setting with cryoablation tools has been shown.^27,28 This approach via median sternotomy has the advantage of direct visualization, fat dissection, and ablation delivered in closer proximity than would be permissible via a percutaneous approach. However, in two published experiences of sequentially staged mapping and ablation, success rates were variable and complications were still reported, including coronary injury and death.

Mulpuru et al. previously reported a robotically assisted approach for LV summit PVC ablation that required minithoracotomy.²⁹ Although mapping was performed with a standard RF catheter in that case, ablation was performed with cryoablation. We recently demonstrated the feasibility of mapping and ablation with a totally endoscopic robotic (DaVinci, Intuitive Surgical, Sunnyvale, CA) approach.³⁰ This was performed with general anesthesia using 5 robotic chest ports (8–15 mm) in a patient with PVC-induced cardiomyopathy with an LV summit origin that was refractory to standard endocardial and percutaneous epicardial ablation. The arrhythmia was mapped using a diagnostic duodecapolar catheter (Livewire, St. Jude Medical, Minneapolis, MN) to an “inaccessible region” that was covered by 10 to 15 mm of epicardial fat superior to the prior epicardial ablation target region (Figure 54.3). After electrocautery-assisted dissection of the fat, an externally irrigated RF ablation catheter (FlexAbility, St. Jude Medical) applied perpendicularly to the epicardium under direct visualization allowed for elimination during the first application. We look forward to this approach being reproduced and validated as a total solution of LV summit arrhythmias that are symptomatic and unable to be eliminated by standard approach.

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