Overview of the New EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias: What You Need to Know

The management of ventricular arrhythmias by catheter ablation is a continually evolving field. A better understanding of arrhythmia mechanisms combined with the diverse range of technologies that have become available make this an exciting area of practice. The recently released EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias1 attempts to put the field into perspective. Experts brought their combined experience and the body of published knowledge together to present the current state of practice and recommendations for future directions. This article summarizes the contents of this excellent reference work. Work of the Task Force The consensus document provides an overview of ventricular arrhythmia mechanisms and rationale for ablation, indications for catheter ablation, technical aspects, the approach to treatment of ventricular tachycardia (VT) in structural heart disease, outcomes of ablation in specific disease states, and a summary of idiopathic ventricular tachycardias with approaches to treatment. In addition, training and institutional requirements and competencies are discussed, as well as clinical trial considerations. The task force defined consensus as 70% or greater member agreement. The various topical areas follow. Ventricular Tachycardia: Definitions, Mechanisms, and Rationale for Ablation Standardization of terminology was the initial task of the group. This was felt to be important so that endpoints, methods, and outcomes would be spoken of in the same language across all treatment centers. A detailed definition list is found in the beginning of the document. The mechanisms of various types of VT provide the rationale for potential cure by catheter ablation. Mechanisms of triggered activity and automaticity, scar-related reentry, and reentry within the Purkinje system are discussed in detail. The approach for idiopathic VT should involve mapping to find a focal origin or a key point on a reentry path. In the case of scar-related VTs, the critical isthmus should be identified and transected. For those with unmappable VTs, larger areas are targeted. With Purkinje reentry, conduction fibers that participate in the circuit are sought and ablated. Indications for VT Ablation Advances in ablation technology and mapping techniques have led to the ablation option for VT being considered much earlier in the treatment course. The consensus group recommendations for VT ablation indications are seen in Tables 1, 2, and 3. Technical Aspects The group recognized the limitations of recommending various newer technologies due to the lack of controlled studies and head-to-head comparisons in the published literature. In addition, the added cost of newer technologies was mentioned. The improved outcomes seen with use of some technologies, however, was considered a positive aspect. It is the hope of the consensus members that clinical trials will be conducted to assess further technological developments. The contribution of newer mapping systems was discussed, both electroanatomic systems and multielectrode arrays. The ability to create chamber geometry and voltage maps has increased success rates and decreased procedure time. The introduction of robotic navigation and magnetic navigation has shortened procedures times, reduced radiation exposure and provided precise and stable catheter navigation in cases involving the atria. However, robotic navigation has not been used in the VT setting, and only a small number of magnetic navigation VT cases have been performed. Imaging has attained a prominent place in the care of the VT ablation patient. Pre-procedural imaging is often performed to confirm anatomical structures. Echocardiography, ventriculography, nuclear imaging, MRI, PET-CT, and CT imaging have been used. In some cases, these images are then integrated into the mapping system to be used during the ablation procedure. During procedures, intracardiac ultrasound is often used to confirm catheter locations. Imaging may also be used post procedure to assess for procedural complications. The most commonly used source of ablation energy is radiofrequency (RF), and there is little experience reported with other sources. RF with 4 or 5 mm electrodes is used for idiopathic VTs, while ablation of scar-related VTs requires a larger lesion, and therefore, the use of larger tipped electrodes or irrigated tip electrodes. There have been no randomized trials comparing VT ablation methods or catheters. Anticoagulation is recommended for all procedures where left heart catheterization takes place. The need for anticoagulation in right-sided heart procedures will be determined by presence of risk factors and procedure length. Pre- and post-procedure anticoagulation is not generally needed in those patients without structural heart disease unless extensive ablation is performed. However, for those with structural heart disease, the possible presence of LV thrombus should be determined. If a laminated thrombus is present, warfarin anticoagulation should be undertaken for 4-6 weeks prior. The presence of any mobile thrombus is an ablation contraindication. The goal for peri-procedure anticoagulation is an ACT of ≥250 s for most cases and >300 s for some electrode arrays and some longer sheaths. Post-procedure anticoagulation with heparin or low-molecular weight heparin is re-started 4-6 hours after hemostasis is achieved, and continued for 12-48 hours. Warfarin is usually begun during this time. Patients are usually placed on aspirin or warfarin for 6-12 weeks post procedure. VT ablation patients are sedated by either conscious sedation or general anesthesia. The choice of method is usually determined by age, risk factors/co-morbidities, and arrhythmia. Meticulous monitoring and care is required with each approach. Antiarrhythmic drugs are usually discontinued for 4-5 half-lives prior to the procedure. If the patient has a poorly tolerated VT, hospitalization prior to the procedure, as the drug washes out, may be required. Patients on amiodarone would be the exception due to the extremely long half-life of the drug. The risks related to catheter ablation were summarized by the group with special attention to those found more specifically in VT cases. These risks include vascular injury, thromboembolism, air embolism, cardiac tamponade, valve injury, damage to the conduction system, myocardial ischemia, heart failure, and radiation. Ventricular Tachycardia in Structural Heart Disease Ventricular tachycardia found with structural heart disease includes scar-related VT from MI, valvular heart disease, myocarditis, sarcoidosis, hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia/cardiomyopathy, Chagas’ disease, and repaired congenital heart disease. Emphasis is placed on a thorough patient evaluation prior to the procedure. A great deal of discussion in the consensus document takes place regarding the mapping of the scar-related VT. Guidelines for the role of electrogram recording and interpretation, activation mapping, pace mapping, entrainment mapping, and substrate mapping are all reviewed. Three endpoints of ablation have been used by various practitioners: 1) non-inducibility of the clinical VT; 2) modification of the induced cycle length; and 3) non-inducibility of any VT.1 The expanding range of disease entities being treated by ablation and the advent of substrate approaches may dictate that some additional endpoints be created. Specifics related to stimulation protocol post procedure are discussed in this section. The proper scenarios for endocardial versus epicardial ablation are reviewed, as are surgical ablation and the use of intracoronary ethanol ablation. Ablation Outcomes and Considerations in Specific Diseases Diagnoses for which there was specific discussion included prior myocardial infarction, non-ischemic dilated cardiomyopathy, surgically repaired congenital heart disease, right ventricular disease, depressed ventricular function associated with frequent ventricular ectopy, bundle branch reentry, and patients with ICDs. Idiopathic Ventricular Tachycardias These tachycardias occur in the absence of structural heart disease or they may occur in the presence of structural problems but not be related to structure. The primary area of concern with these idiopathic tachycardias is that frequency may lead to tachycardia cardiomyopathy, but not usually sudden death. The consensus document discusses in great detail the approach for various idiopathic outflow tract tachycardias, intrafascicular verapamil-sensitive reentrant tachycardia, and polymorphic ventricular tachycardia and ventricular fibrillation. Training and Institutional Requirements and Competencies, and Clinical Trial Considerations The training and institutional requirements and competencies section outlines considerations for safe and successful procedures. Goals for attaining competency are outlined for physicians, staff, and institutions desiring to perform VT ablations. The clinical trial considerations discussion provides a wish list of areas that need exploration, and some great suggestions for research projects! An exceptionally useful table outlines suggested standards for reporting the results of catheter ablation for VT. Incorporation of these standards into clinical reporting would help to ensure that everyone was speaking the same language, and that apples were being compared to apples instead of apples to oranges! Conclusion This expert consensus document should be a required reference for all labs in which VT ablation is taking place. Physicians and lab staff alike can benefit from having this comprehensive reference at their fingertips. For more information, please visit www.hrsonline.org. This document may also be downloaded from: https://www.hrsonline.org/Policy/ClinicalGuidelines/vt-ablation.