Ja s et al reported that complete LAVA
Jaïs et al. reported that complete LAVA elimination is a better predictor of success than the absence of inducibility . Achieving complete elimination of LAVA yields superior survival free from recurrent VT during long-term follow-up. Scar homogenization significantly increases the freedom from VT recurrence . These ablation strategies aim to abolish all potential VT casin occurring from complex arrhythmia substrate and, importantly, do not rely on VT inducibility as a procedural endpoint. However, these studies were not randomized. Further randomized trials with prospective data collection from larger samples are warranted to evaluate the benefits of complete substrate modification in terms of clinical outcome.
Conflict of interest
Introduction Implantable cardioverter defibrillator (ICD) therapy has improved the prognosis of patients with lethal ventricular arrhythmias [1–3]. The ICD terminates episodes of ventricular tachycardia (VT) and saves patients from sudden cardiac death; however, it does not change the arrhythmogenic substrate. Previous studies have shown that patients who receive shock therapy have a poorer prognosis , which suggests the necessity of supplemental preventive therapy to reduce the ICD shock frequency. The indication for antiarrhythmic drugs is strictly limited because of their negative inotropy, proarrhythmic effect, and poor compliance . Catheter ablation is now recognized as the most potent non-pharmacological option to modify the reentrant arrhythmogenic circuit and in some clinical studies has actually been proved to reduce the number of ICD shocks [6,7]. However, poor inducibility of the index VT, concomitant non-clinical VT, and hemodynamic and electrical instability often make it difficult to perform activation mapping during VT. Moreover, radiofrequency energy applied endocardially is sometimes insufficient to create transmural lesions across thick ventricular myocardium. Thus, to achieve success in VT ablation, some novel approaches are required in addition to conventional mapping and ablation techniques. When activation mapping is not available, identification of the substrate that forms the critical part of the reentrant circuit during sinus rhythm enables mapping in a hemodynamically stable condition, and permits a strategy for ablation even in non-inducible patients. The bipolar/unipolar scar identified by the electroanatomical mapping (EAM) system, late enhancement detected by CT/MRI, and late or fractionated local activity could be potential targets for ablation. In a number of cases, the VT circuit could be located in the epicardium or even in an intramural layer. Thus, it is important to identify the substrate optimally at the beginning of the procedure and to prepare an appropriate approach (transaortic, transseptal, or epicardial). With better technology, such as contact force monitoring, high-definition mapping catheters, and new signal processing algorithms, our understanding of VT substrate mapping will improve in the near future. In this article, the present strategy of procedures for the mapping and ablation of VT is reviewed.
Preparation of the procedure
Initial induction of ventricular tachycardia Commonly, VT induction by programmed ventricular stimulation (PVS) is attempted at the beginning of the procedure, except in some cases, such as when clinical VT has already been documented with reproducibility, the patient exhibits incessant or spontaneous VT, and the ablation target is clearly identified. Although the relationship between the inducibility of VT and clinical VT has not been fully elucidated, induced VT provides some useful information . The presence or absence of VT inducibility, the hemodynamic stability or sustainability of the induced VT, and the VT morphologies help to determine the procedure strategy, required support (including extracorporeal circulation or surgical approach), and endpoint.