INTRODUCTION

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited myocardial disease caused by mutations in genes encoding desmosomal proteins that predominantly affects the right ventricle (RV).¹ ARVC is a significant cause of sudden death in young people. Progressive loss of RV myocardium and its fibrofatty replacement is the main pathological finding of the disease. Fibrofatty replacement involves predominantly the RV and initiates at the epicardium becoming transmural at advanced stages of the disease.^2,3 This process generates scar areas with interwoven viable fibers that determine a substrate for ventricular arrhythmias similar to that observed in ischemic heart disease. RV scarring is mainly detected in the subtricuspid and outflow tract areas. Left ventricular involvement is not uncommon, affecting predominantly the posterolateral subepicardium.^4,5

The typical clinical presentation includes ventricular arrhythmias with LBBB morphology, T-wave inversion in right precordial leads, and RV dilatation/regional motion abnormalities in cardiac imaging techniques. Clinical diagnosis is sometimes challenging, particularly at early stages of the disease. Invasive electroanatomic mapping may play a role in the diagnosis of ARVC in patients with inconclusive Task Force Criteria^6,7 (Figure 32.1).

Implantable cardioverter-defibrillator (ICD) is generally recommended to prevent sudden death in high-risk ARVC patients.⁸ Antiarrhythmic drugs often are unable to prevent recurrent ventricular arrhythmias, and amiodarone, the most effective, is associated with important side effects. Catheter ablation is an option for patients with sustained ventricular tachycardia (VT). Radiofrequency ablation has not proved to reduce the risk of sudden death and is usually indicated for the prevention of symptomatic VT episodes and ICD shocks. Therefore, catheter ablation is not recommended as an alternative to ICD for the prevention of sudden cardiac death in ARVC patients.⁹ Endocardial ablation in ARVC has a moderate to low acute success rate and high frequency of VT recurrences, probably revealing the epicardial nature of the disease.^10–12 There is growing literature showing that an endocardial–epicardial approach after unsuccessful endocardial ablation or as first-line obtain better results.^5,13–17 The strategy for selecting patients who will probably benefit most from epicardial ablation is still being debated.

ENDOCARDIAL ABLATION IN ARVC

Initially, endocardial catheter ablation in ARVC was restricted to patients with incessant VT or arrhythmic storm refractory to antiarrhythmic drugs, including amiodarone. First reports of endocardial ablation showed modest results, with frequent VT recurrences in the mid-and long-term follow-up.^10–12,18 There are differences in reported strategies for VT ablation in patients with ARVC. Roughly, long-term success of endocardial ablation using 3D mapping systems and substrate ablation techniques is less than 50%.^11,12 These suboptimal long-term results have been attributed to the progressive nature of the disease. The continuous process of fibro-fatty substitution can generate new circuits that promote recurrent VT. However, a significant proportion of the reported recurrences occur within the first months immediately after ablation, which can hardly be attributed to the progression of the arrhythmogenic substrate.

An alternative explanation for endocardial ablation failure is the epicardial nature of ARVC. Several works have showed a predominant epicardial substrate in ARVC patients.13,17,19 In a series published by our group, the electroanatomical characteristics of endocardium and epicardium were analyzed in 22 consecutive patients with ARVC referred for ablation. We observed that 90% of the isthmuses of the induced VT and 75% of the conduction channels identified during substrate mapping were located on the epicardial surface.²⁰ It has been reported that endocardial ablation allows elimination of epicardial abnormal local ventricular activity (LAVA), which could allow avoiding the epicardial access, potentially associated with serious complications.²¹ Up to 74% of ARVC patients presented epicardial LAVA that could be eliminated from the endocardium. However, in only 33% it was possible to eliminate all the abnormal electrograms from the endocardium.²¹ On the other hand, around 25% of patients with ARVC show a completely normal endocardial map, which would make it difficult to locate and possibly abolish the epicardial substrate from the endocardium.⁵

ENDOCARDIAL–EPICARDIAL ABLATION AFTER PREVIOUSLY FAILED ENDOCARDIAL PROCEDURE

Given the poor long-term outcomes and the characteristic substrate distribution pattern described in ARVC with predominant epicardial involvement,22 Garcia et al. first reported the feasibility and efficacy of epicardial catheter ablation in 13 ARVC patients after previously failed endocardial VT ablation procedures¹⁹ (see Table 32.1). This study demonstrated that the arrhythmogenic substrate was significantly larger in epicardium than endocardium and that VTs dependent on that epicardial substrate had to be targeted at the epicardium either opposite to normal endocardium or opposite to ineffective endocardial ablation sites. Complete acute success was achieved in 85% of cases, and 77% of patients were free of recurrent VT after 18 months of follow-up.¹⁹ Bai et al.¹⁵

Stay updated, free articles. Join our Telegram channel

Join