Ventricular Tachycardia Ablation – The Right Approach for the Right Patient

Abstract

Scar-related reentrant ventricular tachycardia (VT) may be present in a variety of structural heart disease (SHD) phenotypes. In this setting, VT circuits are comprised of viable myocytes separated by fibrosis, allowing for the slow conduction needed to facilitate reentry.1,2 Aetiologies of fibrosis include ischaemic heart disease (IHD), inflammatory conditions, infiltrative cardiomyopathy, dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy and arrhythmogenic right ventricular (RV) dysplasia.Implantable cardioverter defibrillators (ICDs) are the mainstay of therapy for the prevention of sudden cardiac death in patients with SHD.3 However, ICD shocks are associated with diminished quality of life and increased mortality.4-6 Anti-arrhythmic drugs (AADs) have an important role in shock reduction; however these agents often have limited efficacy and significant side-effects. 7,8 Catheter ablation has assumed an increasingly important role in the management of VT. In patients with IHD and drug-refractory VT, ablation has been shown to reduce arrhythmia recurrence and ICD therapies. 9-11Patients who have VT rendered non-inducible by an ablation procedure have a lower VT recurrence rate and mortality compared with those who still have inducible arrhythmias after the ablation.12 Catheter ablation has also been shown to be effective in the treatment of VT storm in patients with SHD receiving chronic AAD therapy. 13In the setting of non-ischaemic SHD, catheter ablation outcome varies according to the nature of the underlying heart disease, with a greater need for epicardial mapping and ablation, higher recurrence rate and more AAD use in long-term follow-up.14-16 For the most part, VT ablation remains underutilised and some patients may benefit from earlier intervention. 17Although ablation also has an important role in the management of patients with idiopathic VT, this review will focus on ablation of scarrelated reentrant VT, the most common mechanism of monomorphic VT in patients with SHD. Pre-procedural PlanningHeart failure optimisation is important for decreasing the risk of Electrocardiographic CharacterisationTwelve-lead electrocardiograms (ECGs) of all clinical VTs are important in localising VT exit sites, identifying potential ablation targets and directing the best ablation strategy including possible epicardial access.In the setting of non-ischaemic IHD, morphological criteria suggesting Abstract Scar-related reentry is the most common mechanism of monomorphic ventricular tachycardia (VT) in patients with structural heart disease. Catheter ablation has assumed an increasingly important role in the management of VT in this setting, and has been shown to reduce VT recurrence and implantable cardioverter defibrillator (ICD) shocks. The approach to mapping and ablation will depend on the underlying heart disease etiology, VT inducibility and haemodynamic stability. This review explores pre-procedural planning, approach to ablation of both mappable and unmappable VT, and post-procedural testing. Future de...

Mapping of ventricular tachycardia in patients with ischemic cardiomyopathy: Current approaches and future perspectives

“…Pace mapping consists in pacing from areas of abnormal electrogram (EGMs) in and around the scar, in an attempt to match the clinical VT morphology, and can help to approximate the anatomic location of VT . Pacing from within the scar can also identify slow‐conduction channels, which are marked by a prolonged stimulus to QRS interval (S‐QRS), while pacing at the VT exit site will yield a “matched” QRS with a short S‐QRS.…”

“…Lately, techniques involving electrical isolation of the scar (scar isolation and core isolation, Figure F) have been developed . Tilz et al hypothesized that, in selected post‐myocardial infarction (MI) patients with a circumscribed scar, encircling the arrhythmogenic area would be feasible and cause electrical dissociation of the isolated area from the remainder of the left ventricle, while Tzou et al proposed the “core isolation” approach.…”

“…In many substrate mapping strategies, abnormal electrograms are the targets of mapping and ablation. Some studies have regarded all abnormal electrograms (LAVA) as the ablation target, while others have considered only LPs …”

“…Conventional mapping techniques (activation mapping and entrainment mapping) have been used to define the mechanism of tolerated arrhythmias and to identify a critical re-entry isthmus and the potential ablation sites. 9 Entrainment mapping is a technique that uses pacing to confirm the re-entrant mechanism of VT and identify critical and noncritical areas of a VT circuit helping classify pacing sites as isthmus, bystander, and inner or outer loop sites of the VT circuit. 10 Alternative ablation methods involving mapping and ablation in sinus or paced rhythm have been developed for patients with unmappable VT although they are also commonly used also in patients with tolerated VTs.…”

“…E, Ablation of local abnormal ventricular activity (LAVA) and late potentials (LPs). F, Core isolation Pace mapping consists in pacing from areas of abnormal electrogram (EGMs) in and around the scar, in an attempt to match the clinical VT morphology, and can help to approximate the anatomic location of VT. 9 Pacing from within the scar can also identify slowconduction channels, which are marked by a prolonged stimulus to QRS interval (S-QRS), 16 while pacing at the VT exit site will yield a "matched" QRS with a short S-QRS. Recently, it has been recognized that an abrupt transition between a paced-QRS that matches the clinical VT (exit site) and a nonmatched paced-QRS (entrance site) can identify an isthmus.…”