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Catheter ablation of ventricular tachycardia associated with structural heart disease: Current status and perspectives

Published:October 01, 2022DOI:https://doi.org/10.1016/j.jjcc.2022.09.008

      Highlights

      • Catheter ablation is a safe and effective therapy that can reduce recurrent scar-related ventricular tachycardia (VT).
      • New physiological mapping techniques are being used increasingly to complement traditional entrainment mapping techniques.
      • Early VT detection, along with early treatment by catheter ablation, has effectively reduced recurrent VT and hospitalizations.
      • VT ablation is a rapidly developing field that is likely to change the therapeutic landscape in the upcoming years.
      • In addition, such ablation is likely to improve the life expectancy of patients with severe structural heart disease.

      Abstract

      Catheter ablation is an effective and safe treatment for ventricular tachycardia attributable to structural heart disease, reducing the risk of recurrent arrhythmias and defibrillator shock therapy. Advances in medical technology and an accumulation of data have led to the development of detailed guidelines. Successful ablation requires accurate identification of the arrhythmia substrate and effective delivery of radiofrequency energy to the target tissue. Modern practice requires use of traditional electrophysiological mapping processes such as entrainment mapping and three-dimensional activation sequence mapping in combination with newer functional mapping techniques for which there is growing support. Thorough non-invasive preoperative assessment is also necessary before an invasive procedure is undertaken. In this review, we summarize contemporary practice and recent randomized controlled trials underpinning the latest developments in mapping and ablation and discuss potential future developments in this field.

      Graphical abstract

      Keywords

      Introduction

      Ventricular tachycardia (VT) is a significant cause of morbidity and mortality in patients with either ischemic cardiomyopathy (ICM) or non-ischemic cardiomyopathy (NICM) [
      • Al-Khatib S.M.
      • Stevenson W.G.
      • Ackerman M.J.
      • Bryant W.J.
      • Callans D.J.
      • Curtis A.B.
      • et al.
      2017 AHA/ACC/HRS guideline for Management of Patients with Ventricular Arrhythmias and the prevention of sudden cardiac death: executive summary: a report of the american College of Cardiology/American Heart Association task force on clinical practice guidelines and the Heart Rhythm Society.
      ]. Although prognosis has improved with guideline-directed medical therapy, use of implantable cardioverter defibrillators (ICDs), and use of cardiac resynchronization therapy devices, patients continue to experience recurrent VT with appropriate ICD shocks, cardiac hospitalizations, and VT-associated morbidity and mortality [
      • Al-Khatib S.M.
      • Stevenson W.G.
      • Ackerman M.J.
      • Bryant W.J.
      • Callans D.J.
      • Curtis A.B.
      • et al.
      2017 AHA/ACC/HRS guideline for Management of Patients with Ventricular Arrhythmias and the prevention of sudden cardiac death: executive summary: a report of the american College of Cardiology/American Heart Association task force on clinical practice guidelines and the Heart Rhythm Society.
      ,
      • Epstein A.E.
      • DiMarco J.P.
      • Ellenbogen K.A.
      • Estes III, N.A.
      • Freedman R.A.
      • Gettes L.S.
      ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons.
      ,
      • Heidenreich P.A.
      • Bozkurt B.
      • Aguilar D.
      • Allen L.A.
      • Byun J.J.
      • Colvin M.M.
      • et al.
      2022 AHA/ACC/HFSA guideline for the management of heart failure: a report of the american College of Cardiology/American Heart Association joint committee on clinical practice guidelines.
      ]. Antiarrhythmic drug (AAD) therapy is commonly used for recurrent ventricular arrhythmias. However, AADs are not without significant side effects, and patients can suffer pulmonary or hepatic toxicity (an effect of amiodarone) [
      • Sapp J.L.
      • Wells G.A.
      • Parkash R.
      • Stevenson W.G.
      • Blier L.
      • Sarrazin J.F.
      • et al.
      Ventricular tachycardia ablation versus escalation of antiarrhythmic drugs.
      ], aggravation of the arrhythmia, or bradyarrhythmia, which may increase the need for pacing, potentially aggravating the ventricular dysfunction. Further, limitations in AAD-based control of arrhythmia over the long-term have been recognized [
      • Packer D.L.
      • Prutkin J.M.
      • Hellkamp A.S.
      • Mitchell L.B.
      • Bernstein R.C.
      • Wood F.
      • et al.
      Impact of implantable cardioverter-defibrillator, amiodarone, and placebo on the mode of death in stable patients with heart failure: analysis from the sudden cardiac death in heart failure trial.
      ]. Radiofrequency (RF) catheter ablation is an established adjunctive treatment option for VT in patients with cardiomyopathy, particularly those with a ventricular arrhythmia refractory to AAD therapy and those who cannot tolerate AADs. There have been numerous reports providing evidence that RF ablation, in addition to use of advanced technologies, can be used to improve clinical outcomes, even life expectancy, of patients with VT associated with structural heart disease.
      Herein, we review and discuss the reported evidence that RF ablation, used in addition to advanced technologies, can improve clinical outcomes, even life expectancy, of patients with VT associated with structural heart disease.

      Indications

      For VT associated with structural heart disease, expert consensus guidelines currently recommend catheter ablation of the VT after the failure of AAD therapy and for patients in whom AAD therapy is either not tolerated or not desired (class I indication) [
      • Cronin E.M.
      • Bogun F.M.
      • Maury P.
      • Peichl P.
      • Chen M.
      • Namboodiri N.
      • et al.
      2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.
      ]. The Japanese guideline recommendations for catheter ablation of sustained monomorphic VT in patients with structural heart disease are shown in Table 1 (JCS/JHRS 2019 Guideline) [
      • Nogami A.
      • Kurita T.
      • Abe H.
      • Ando K.
      • Ishikawa T.
      • Imai K.
      • et al.
      JCS/JHRS 2019 guideline on non-pharmacotherapy of cardiac arrhythmias.
      ].
      Table 1Indications for catheter ablation of sustained monomorphic VT in patients with structural heart disease (modified from the JCS/JHRS 2019 guideline).
      Class I indication
      In patients with structural heart disease and incessant monomorphic VT or VT storm, for whom AADs are ineffective or not tolerated, catheter ablation is recommended.
      In patients with ICM and symptomatic sustained monomorphic VT for whom AADs are ineffective or not tolerated, catheter ablation is recommended.
      In patients with ICM, sustained monomorphic VT, and an ICD who experience frequent ICD therapies, catheter ablation is recommended.
      In patients with ICM who experience recurrent monomorphic VT despite chronic amiodarone therapy, catheter ablation is

      recommended in preference to escalating AAD therapy.
      In patients with bundle branch reentrant VT, catheter ablation is recommended for reducing the risk of recurrent VT.
      Class IIa indication
      In patients with ICM and sustained monomorphic VT who undergo an ICD implantation, perioperative catheter ablation should be considered to reduce the risk of recurrent VT or ICD therapies.
      In patients with non-ischemic cardiomyopathy and sustained monomorphic VT for whom AADs are ineffective or not tolerated, catheter ablation should be considered.
      AAD, antiarrhythmic drug; ICD, implantable cardioverter-defibrillator; ICM, ischemic cardiomyopathy; VT, ventricular tachycardia.
      Whether catheter ablation is indicated for sustained VT should be determined under careful consideration of the risks and benefits with respect to the patient's general condition and the physician's level of experience. In cases of sustained VT associated with a history of myocardial infarction or structural heart disease such as cardiomyopathy, ICD implantation is the mainstay for prevention of sudden death [
      • Moss A.J.
      • Hall W.J.
      • Cannom D.S.
      • Daubert J.P.
      • Higgins S.L.
      • Klein H.
      • et al.
      Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. Multicenter automatic defibrillator implantation trial investigators.
      ,
      • Moss A.J.
      • Zareba W.
      • Hall W.J.
      • Klein H.
      • Wilber D.J.
      • Cannom D.S.
      • et al.
      Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction.
      ]. However, frequent VT attacks and ICD-delivered shocks have been reported to worsen patients' quality of life and to increase the risk of all-cause death [
      • Moss A.J.
      • Greenberg H.
      • Case R.B.
      • Zareba W.
      • Hall W.J.
      • Brown M.W.
      • et al.
      Long-term clinical course of patients after termination of ventricular tachyarrhythmia by an implanted defibrillator.
      ,
      • Mark D.B.
      • Anstrom K.J.
      • Sun J.L.
      • Clapp-Channing N.E.
      • Tsiatis A.A.
      • Davidson-Ray L.
      • et al.
      Quality of life with defibrillator therapy or amiodarone in heart failure.
      ,
      • Daubert J.P.
      • Zareba W.
      • Cannom D.S.
      • McNitt S.
      • Rosero S.Z.
      • Wang P.
      • et al.
      Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.
      ,
      • Poole J.E.
      • Johnson G.W.
      • Hellkamp A.S.
      • Anderson J.
      • Callans D.J.
      • Raitt M.H.
      • et al.
      Prognostic importance of defibrillator shocks in patients with heart failure.
      ]. In cases of VT or ventricular fibrillation associated with hemodynamic compromise, the patient is more likely to experience syncope even if the ICD is activated, and in patients in the conscious state, DC shocks can cause fear and discomfort [
      • Daubert J.P.
      • Zareba W.
      • Cannom D.S.
      • McNitt S.
      • Rosero S.Z.
      • Wang P.
      • et al.
      Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.
      ,
      • Poole J.E.
      • Johnson G.W.
      • Hellkamp A.S.
      • Anderson J.
      • Callans D.J.
      • Raitt M.H.
      • et al.
      Prognostic importance of defibrillator shocks in patients with heart failure.
      ]. Concomitant use of AADs reduces the frequency of ICD shocks, but it is not curative, and there are potential side effects [
      • Marchlinski F.E.
      • Haffajee C.I.
      • Beshai J.F.
      • Dickfeld T.L.
      • Gonzalez M.D.
      • Hsia H.H.
      • et al.
      Long-term success of irrigated radiofrequency catheter ablation of sustained ventricular tachycardia: post-approval THERMOCOOL VT trial.
      ]. Catheter ablation of sustained VT due to structural heart disease is a complicated procedure requiring technical proficiency, and the arrhythmia often recurs. However, such technological advances as 3D mapping systems [
      • Takigawa M.
      • Frontera A.
      • Thompson N.
      • Capellino S.
      • Jais P.
      • Sacher F.
      The electrical circuit of a hemodynamically unstable and recurrent ventricular tachycardia diagnosed in 35 s with the rhythmia mapping system.
      ,
      • Viswanathan K.
      • Mantziari L.
      • Butcher C.
      • Hodkinson E.
      • Lim E.
      • Khan H.
      • et al.
      Evaluation of a novel high-resolution mapping system for catheter ablation of ventricular arrhythmias.
      ] and irrigated tip ablation catheters [
      • Marchlinski F.E.
      • Haffajee C.I.
      • Beshai J.F.
      • Dickfeld T.L.
      • Gonzalez M.D.
      • Hsia H.H.
      • et al.
      Long-term success of irrigated radiofrequency catheter ablation of sustained ventricular tachycardia: post-approval THERMOCOOL VT trial.
      ,
      • Tanner H.
      • Hindricks G.
      • Volkmer M.
      • Furniss S.
      • Kuhlkamp V.
      • Lacroix D.
      • et al.
      Catheter ablation of recurrent scar-related ventricular tachycardia using electroanatomical mapping and irrigated ablation technology: results of the prospective multicenter euro-VT-study.
      ] used in combination with cardiac magnetic resonance imaging (MRI), have significantly improved outcomes [
      • Andreu D.
      • Penela D.
      • Acosta J.
      • Fernandez-Armenta J.
      • Perea R.J.
      • Soto-Iglesias D.
      • et al.
      Cardiac magnetic resonance-aided scar dechanneling: influence on acute and long-term outcomes.
      ,
      • Siontis K.C.
      • Kim H.M.
      • Sharaf Dabbagh G.
      • Latchamsetty R.
      • Stojanovska J.
      • Jongnarangsin K.
      • et al.
      Association of preprocedural cardiac magnetic resonance imaging with outcomes of ventricular tachycardia ablation in patients with idiopathic dilated cardiomyopathy.
      ].
      Several randomized controlled trials (RCTs) on ablation before or after ICD implantation for sustained VT associated with a prior myocardial infarction have been conducted [
      • Al-Khatib S.M.
      • Daubert J.P.
      • Anstrom K.J.
      • Daoud E.G.
      • Gonzalez M.
      • Saba S.
      • et al.
      Catheter ablation for ventricular tachycardia in patients with an implantable cardioverter defibrillator (CALYPSO) pilot trial.
      ]. The SMASH-VT [
      • Reddy V.Y.
      • Reynolds M.R.
      • Neuzil P.
      • Richardson A.W.
      • Taborsky M.
      • Jongnarangsin K.
      • et al.
      Prophylactic catheter ablation for the prevention of defibrillator therapy.
      ] and VTACH [
      • Kuck K.H.
      • Schaumann A.
      • Eckardt L.
      • Willems S.
      • Ventura R.
      • Delacretaz E.
      • et al.
      Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial.
      ] trials showed significantly fewer ICD interventions in ablation group patients than in non-ablation group patients. However, in a CALYPSO pilot study [
      • Al-Khatib S.M.
      • Daubert J.P.
      • Anstrom K.J.
      • Daoud E.G.
      • Gonzalez M.
      • Saba S.
      • et al.
      Catheter ablation for ventricular tachycardia in patients with an implantable cardioverter defibrillator (CALYPSO) pilot trial.
      ] that compared ablation treatment against AAD treatment, non-superiority of the ablation treatment over the AAD treatment was found. The VANISH trial [
      • Sapp J.L.
      • Wells G.A.
      • Parkash R.
      • Stevenson W.G.
      • Blier L.
      • Sarrazin J.F.
      • et al.
      Ventricular tachycardia ablation versus escalation of antiarrhythmic drugs.
      ], which compared ablation and AAD escalation in patients with post-myocardial infarction VT, showed significantly fewer ICD shocks in the ablation therapy arm. Thus, sustained VT with underlying ICM is now considered a class I indication for ablation (Table 1).
      In comparative studies of ICM and NICM [NICM is a broad term that includes dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy (HCM), cardiac sarcoidosis, arrhythmogenic right ventricular cardiomyopathy (ARVC), and lamin A/C-related cardiomyopathy] as the underlying diseases, the VT-free rates after ablation were lower among NICM patients than among ICM patients, and VT inducibility was found to be a prognostic factor [
      • Dinov B.
      • Fiedler L.
      • Schonbauer R.
      • Bollmann A.
      • Rolf S.
      • Piorkowski C.
      • et al.
      Outcomes in catheter ablation of ventricular tachycardia in dilated nonischemic cardiomyopathy compared with ischemic cardiomyopathy: results from the prospective heart Centre of Leipzig VT (HELP-VT) study.
      ,
      • Tung R.
      • Vaseghi M.
      • Frankel D.S.
      • Vergara P.
      • Di Biase L.
      • Nagashima K.
      • et al.
      Freedom from recurrent ventricular tachycardia after catheter ablation is associated with improved survival in patients with structural heart disease: an international VT ablation center collaborative group study.
      ]. Accordingly, sustained monomorphic VT in patients with NICM is now considered a Class IIa indication in the Japanese guidelines [
      • Nogami A.
      • Kurita T.
      • Abe H.
      • Ando K.
      • Ishikawa T.
      • Imai K.
      • et al.
      JCS/JHRS 2019 guideline on non-pharmacotherapy of cardiac arrhythmias.
      ]; the substrate for reentry is often located in the mid-myocardium or epicardium, making the ablation procedure more difficult.

      RF catheter ablation of ventricular arrhythmias

      Effective catheter ablation of scar-related VT is of two critical components. The first is substrate identification, i.e. identification of the critical substrates involved in the initiation and/or maintenance of the arrhythmia. Substrate identification requires assimilation of all available data, including detailed analysis of the patient's electrocardiogram (ECG), pre-procedure investigations, successful induction and mapping of specific VT circuits, and information obtained from invasive mapping performed during baseline rhythm. The second is the ablation itself, i.e. delivery of sufficient energy to the target tissue to ensure permanent destruction and prevent further ventricular arrhythmia. The following is a typical VT substrate identification method.

      Entrainment mapping

      Entrainment mapping has been used for >30 years to discriminate VT circuits. It does not require advanced mapping systems and can be performed simply with the use of ECG recordings and a stimulation device (Fig. 1A ). Ideally, induction of VT must be reproducible, the QRS morphology must be uniform from beat to beat, and the VT must be sustained and hemodynamically stable. These conditions are often not met in patients with structural heart disease. In cases of scar-related VT (e.g. ICM), finding a protected region of diastolic activity used as an essential part of the reentrant circuit is desirable because ablation at this site is likely to eliminate the tachycardia. As a result of significant changes in electrophysiology resulting from the previous injury (e.g. from infarction or myopathy), many sites in the ventricle may show diastolic activation but may not be related to the sustained VT. These “bystander sites” make activation mapping more difficult. Pacing techniques such as entrainment can determine whether a site is part of the circuit or a bystander. When pacing is stopped and the tachycardia resumes, the time of the first compound relative to the last paced beat indicates how close the pacing site is to part of the VT circuit (Fig. 1A). During entrainment, the paced wavefront activates a part of the ventricle, and part is forced to leave the circuit earlier than normal, resulting in a fusion complex on the ECG. Pacing from within a critical portion of the circuit produces a QRS complex that matches that of the VT; fusion occurs only within the circuit and is “concealed,” Sites with low-amplitude, isolated mid-diastolic potentials that cannot be separated from the tachycardia by pacing perturbations and where entrainment with concealed fusion can be demonstrated are very likely to be sites for successful ablation (Fig. 1B).
      Fig. 1
      Fig. 1Identification of the ventricular tachycardia (VT) circuit by classic diagnostic methods and by means of electroanatomical mapping. (A) “Concealed” entrainment of post-infarction VT. The three complexes on the left represent pacing during VT, with a stimulus (St)-QRS interval of 62 ms. Once pacing ends, the VT resumes. The electrogram (arrow) in Abl D (distal electrode pair of the ablation catheter) is 62 ms before QRS onset. The paced and VT QRS complexes are almost identical. (B) Ablation at this site terminated the VT. (C) Activation map displayed during the tachycardia in the same case as on the left, showing the VT to be of a figure-of-eight reentry pattern with eight time components: white, red, orange, yellow, light green, light blue, blue, and purple. Notably, most red components bear right ventricular (RV) activation, suggesting a complex three-dimensional VT circuit rather than a two-dimensional circuit. The site of tachycardia cessation shown in A, i.e. the isthmus (narrow corridor) of the VT, is indicated by an arrow. (D) Voltage map obtained during sinus rhythm in the same case. (E) Isochronal late activation map (ILAM) obtained during sinus rhythm in the same case. As in panel C, it is shown with eight time components. The transmission velocity is heterogeneous due to damaged cardiac tissue. The shortest distance between time phases is the deceleration zone (DZ). The time phase immediately before the most delayed time phase (purple) is the DZ, which can be seen to be in spatial proximity to the tachycardia termination site (panel C) and also the late potential recording site (panel E) during sinus rhythm. (F) Late potential recording obtained with an Advisor HD Grid Mapping Catheter with 16 electrodes. Late potentials are recorded extensively around the DZ shown in panel D.

      Activation mapping during VT

      Activation mapping determines the overall pattern of ventricular myocardial activation from the timing of the regional ECG and in reference to a particular time point (e.g. start of the QRS complex). This process is mainly automated with use of electroanatomical mapping software.
      In scar-related reentrant VT, the activation map requires a different interpretation. This is because activation has no focal point; there exists, rather, a continuous circuit of electrical activity (Fig. 1C): the local ECG signal just before the QRS represents the point at which the wavefront exits the protected canal into the myocardium, and the presence of a mid-diastolic potential identifies electrical activity through the critical isthmus. However, slow passive conduction is common within scar tissue, and the mid-diastolic activation alone is insufficient to determine any active involvement in the reentrant circuit. Therefore, the essential components of the re-entry circuit can be accurately identified only by entrainment mapping. Basically, entrainment pacing is performed on the presumed site of the critical isthmus of the VT delineated on the electroanatomic map (EAM) to confirm that it is the optimal site for treatment.

      Substrate mapping during the baseline rhythm

      In a significant proportion of patients with VT and structural heart disease, activation mapping and entrainment cannot be performed due to a patient's low hemodynamic tolerance during arrhythmia or to failure to initiate sustained tachycardia during the electrophysiological study. In these circumstances, an additional method, substrate mapping, can be used. Substrate mapping involves both voltage amplitude-mapping and activation mapping during sinus or baseline rhythm.
      The local ECG amplitudes can distinguish between normal and scar tissue, and automated bipolar and unipolar voltage maps are generated and displayed on a three-dimensional EAM. Normal bipolar voltage of the endocardium, measured between two adjacent electrodes on the endocardial surface, is generally considered to be above 1.5 mV, whereas bipolar voltage below 0.5 mV identifies dense scar [
      • Marchlinski F.E.
      • Callans D.J.
      • Gottlieb C.D.
      • Zado E.
      Linear ablation lesions for control of unmappable ventricular tachycardia in patients with ischemic and nonischemic cardiomyopathy.
      ] (Fig. 1D). The multipolar catheters allow for estimated localization of channels supporting VT on the high-density voltage map. However, to accurately identify the VT channels with relatively high voltages (within areas of low-voltage scarring), voltage-limiting adjustments may be necessary [
      • Mountantonakis S.E.
      • Park R.E.
      • Frankel D.S.
      • Hutchinson M.D.
      • Dixit S.
      • Cooper J.
      • et al.
      Relationship between voltage map "channels" and the location of critical isthmus sites in patients with post-infarction cardiomyopathy and ventricular tachycardia.
      ]. Tung et al. created separate voltage maps using different activation wavefronts (right ventricular pacing, left ventricular pacing, and intrinsic conduction) and re-entry in which approximately 18 % of the critical areas of the VT were found in regions where the voltage was low in one activation wavefront and normal (>1.5 mV) in another activation wavefront [
      • Tung R.
      • Josephson M.E.
      • Bradfield J.S.
      • Shivkumar K.
      Directional influences of ventricular activation on myocardial scar characterization: voltage mapping with multiple wavefronts during ventricular tachycardia ablation.
      ]. Further, a recent trial on post-myocardial infarction remodeling suggested a move away from the standard range for accurately identifying substrates [
      • Sramko M.
      • Abdel-Kafi S.
      • van der Geest R.J.
      • de Riva M.
      • Glashan C.A.
      • Lamb H.J.
      • et al.
      New adjusted cutoffs for "Normal" endocardial voltages in patients with post-infarct LV remodeling.
      ].
      Isochronal late activation maps (ILAMs), created during sinus rhythm or ventricular pacing, have been proposed as complementary materials for identifying critical ablation targets. An example ILAM is shown in Fig. 1E. ILAMs are easily created with electroanatomic mapping software. Local ECGs are timed according to the latest bipolar component, meaning the completion of local activation, and are displayed across isochrones that are equally distributed. Where the conduction velocity slows, isochrones appear densely packed, allowing the “deceleration zone” to be identified [
      • Aziz Z.
      • Shatz D.
      • Raiman M.
      • Upadhyay G.A.
      • Beaser A.D.
      • Besser S.A.
      • et al.
      Targeted ablation of ventricular tachycardia guided by wavefront discontinuities during sinus rhythm: a new functional substrate mapping strategy.
      ]. VT ablation guided by creation of an ILAM has also been performed prospectively, and in 95 % of cases, the site of termination coincided with the deceleration zone, with high rates of freedom from VT at 12 months [
      • Aziz Z.
      • Shatz D.
      • Raiman M.
      • Upadhyay G.A.
      • Beaser A.D.
      • Besser S.A.
      • et al.
      Targeted ablation of ventricular tachycardia guided by wavefront discontinuities during sinus rhythm: a new functional substrate mapping strategy.
      ].
      Late potentials are seen as local ECGs that occur after the terminal portion of the surface QRS, either because they are entirely isolated from other local activity or because of continuous fractionation. They are found in most patients who have suffered myocardial infarction and can be easily identified by mapping during sinus rhythm. An example late potential recording is given in Fig. 1F. Removal of all late potential sites is a possible endpoint of a substrate-based ablation strategy. In a large study of patients with ischemic cardiomyopathy, a combined endpoint of non-induction and removal of all late potentials was employed, and a low incidence of recurrent VT and a significant reduction in cardiac deaths were observed [
      • Silberbauer J.
      • Oloriz T.
      • Maccabelli G.
      • Tsiachris D.
      • Baratto F.
      • Vergara P.
      • et al.
      Noninducibility and late potential abolition: a novel combined prognostic procedural end point for catheter ablation of postinfarction ventricular tachycardia.
      ]. The study, however, was not an RCT.

      Pace mapping technique

      Pace mapping serves as a corroborative method for localizing the VT circuit. It can be used to identify the presumptive exit or isthmus region of the VT circuit but is not sufficiently specific or sensitive to be the sole guide for ablation. Pace mapping in normal sinus rhythm after VT termination is attempted at potential isthmus sites (as identified by activation and entrainment mapping during VT). The resulting 12-lead ECG morphology is compared with that of the VT. Automated pace map matching is now available in some recording and electroanatomic mapping systems. The greater the degree of concordance between the morphology during pacing and the tachycardia, the closer the catheter is to the exit zone of the VT isthmus. Evaluation of the S-QRS interval is also of value. Sites at which pace mapping produces the same QRS morphology as that of the initial isthmus site but with different S-QRS delays are identified to trace the course of the VT isthmus.
      Recently, pace mapping was also used to unmask the VT isthmus in patients with re-entrant VT after myocardial infarction [
      • de Chillou C.
      • Groben L.
      • Magnin-Poull I.
      • Andronache M.
      • MagdiAbbas M.
      • Zhang N.
      • et al.
      Localizing the critical isthmus of postinfarct ventricular tachycardia: the value of pace-mapping during sinus rhythm.
      ]. In that study, as expected, the highest pace map ratio was found at the exit of the isthmus, and the lowest was found near the entrance site of the isthmus. Therefore, on high-density 3D pace maps, abrupt changes in pace map match ratios are associated with the central isthmus, consistent with the location of the wavefronts identified by activation mapping.
      It is now standard practice at many centers to search for the VT substrate by means of the methods described above and to deliver adequate RF energy to the target tissue to remove the substrate.

      Latest trends in catheter ablation of VT

      New ECG definitions and 3D maps that represent functional substrates of VT, such as local abnormal ventricular activity and decremental evoked potentials, have been reported to indicate optimal treatment sites [
      • Porta-Sanchez A.
      • Jackson N.
      • Lukac P.
      • Kristiansen S.B.
      • Nielsen J.M.
      • Gizurarson S.
      • et al.
      Multicenter study of ischemic ventricular tachycardia ablation with decrement-evoked potential (DEEP) mapping with extra stimulus.
      ,
      • Jais P.
      • Maury P.
      • Khairy P.
      • Sacher F.
      • Nault I.
      • Komatsu Y.
      • et al.
      Elimination of local abnormal ventricular activities: a new end point for substrate modification in patients with scar-related ventricular tachycardia.
      ]. Efforts to incorporate ventricular premature stimulation during mapping, rather than fixed rhythms, such as sinus rhythm or a pacing rhythm, to find decremental properties that characterize substrates and target tissues for VT have been actively pursued in recent years. Tung et al., using high-density detailed endocardial and epicardial mapping, reported that most myocardial reentries are characterized by complex three-dimensional (3D) activation patterns and heterogeneous transmuralities, with rare two-dimensional planar configurations (see the activation map in Fig. 1C) [
      • Tung R.
      • Raiman M.
      • Liao H.
      • Zhan X.
      • Chung F.P.
      • Nagel R.
      • et al.
      Simultaneous endocardial and epicardial delineation of 3D reentrant ventricular tachycardia.
      ]. It is no exaggeration to say that state-of-the-art methodologies and technologies have unraveled the complex VT circuitry that results from the extensive and heterogeneous damage to the 3D myocardial architecture caused by structural heart disease.
      Careful pre-procedure inspection seems to be essential to finding the decremental conduction properties within the complex substrate in the limited time available during the ablation procedure. Thus, thorough preoperative substrate localization based on surface 12-lead ECG, non-invasive ECG imaging, and contrast-enhanced MRI [
      • Andreu D.
      • Penela D.
      • Acosta J.
      • Fernandez-Armenta J.
      • Perea R.J.
      • Soto-Iglesias D.
      • et al.
      Cardiac magnetic resonance-aided scar dechanneling: influence on acute and long-term outcomes.
      ,
      • Siontis K.C.
      • Kim H.M.
      • Sharaf Dabbagh G.
      • Latchamsetty R.
      • Stojanovska J.
      • Jongnarangsin K.
      • et al.
      Association of preprocedural cardiac magnetic resonance imaging with outcomes of ventricular tachycardia ablation in patients with idiopathic dilated cardiomyopathy.
      ,
      • Graham A.J.
      • Orini M.
      • Zacur E.
      • Dhillon G.
      • Daw H.
      • Srinivasan N.T.
      • et al.
      Simultaneous comparison of electrocardiographic imaging and epicardial contact mapping in structural heart disease.
      ], as well as sensitive and systematic mapping and ablation, will contribute to improved outcomes.

      New ablation and mapping technologies

      Omnipolar technology

      Omnipolar ECGs are being used increasingly to create ventricular EAMs. An actual example created with use of the Advisor HD Grid Mapping Catheter (Abbott, St Paul, MN, USA) is shown in Fig. 1F. This new approach to voltage mapping makes use of the directionality of the electric field of the wavefront traveling over the myocardial surface. Preliminary studies have shown that omnipolar ECGs are directionally independent and virtual bipolar ECGs aligned along the direction of the wavefront [
      • Deno D.C.
      • Balachandran R.
      • Morgan D.
      • Ahmad F.
      • Masse S.
      • Nanthakumar K.
      Orientation-independent catheter-based characterization of myocardial activation.
      ]. Omnipolar ECG-based ventricular mapping has been achieved in animal models, but whether this technology is clinically applicable to ablation of VT remains unclear.

      Retrograde coronary venous ethanol

      RF ablation of VT may fail due to lack of access to the critical substrate. For example, in left ventricular summit VT, the critical substrate may be identified only by mapping the coronary sinus and its tributaries. In multicenter prospective trials, retrograde coronary venous ethanol was shown to be safe and effective and to provide long-term control of drug- and RF-refractory ventricular arrhythmias. In an earlier study, use of single-agent or adjunctive retrograde coronary ethanol was successful in 98 % of patients (n = 56), 77 % of whom remained relapse-free at 12 months [
      • Tavares L.
      • Lador A.
      • Fuentes S.
      • Da-Wariboko A.
      • Blaszyk K.
      • Malaczynska-Rajpold K.
      • et al.
      Intramural venous ethanol infusion for refractory ventricular arrhythmias: outcomes of a multicenter experience.
      ].

      Stereotactic body radiotherapy

      Radiotherapy is a long-established treatment modality that delivers high-energy X-, gamma-, and photon-rays to abnormal tissue (mainly cancer cells). In recent years, animal models have shown that myocardial irradiation induces percutaneous fibrosis similar to catheter ablation, and radiotherapy has gained attention as treatment for arrhythmias [
      • Blanck O.
      • Bode F.
      • Gebhard M.
      • Hunold P.
      • Brandt S.
      • Bruder R.
      • et al.
      Dose-escalation study for cardiac radiosurgery in a porcine model.
      ]. In a series of 5 patients with refractory VT, high-density surface mapping achieved with a 252-electrode ECG vest was used to characterize the VT and combined with chest CT to define the substrate in a completely non-invasive manner [
      • Cuculich P.S.
      • Schill M.R.
      • Kashani R.
      • Mutic S.
      • Lang A.
      • Cooper D.
      • et al.
      Noninvasive cardiac radiation for ablation of ventricular tachycardia.
      ]. After treatment, 99.9 % reduction in the total VT burden was observed. However, the evidence supporting non-invasive stereotactic radiotherapy is limited to small case reports and RCTs are needed.

      Recent RCTs and future directions

      VT is associated with severe cardiac disease, and the occurrence of VT itself reduces cardiac function. The occurrence of VT, particularly occurrence of an ICD shock for VT, predicts subsequent hospitalizations or death from heart failure [
      • Samuel M.
      • Elsokkari I.
      • Sapp J.L.
      Ventricular tachycardia burden and mortality: association or Causality?.
      ]. Therefore, we can argue, on a biological basis, that preventing VT by catheter ablation reduces heart failure and improves the survival.
      The VANISH trial showed a treatment benefit when catheter ablation was added to ICD implantation in patients with ICM but no difference in mortality [
      • Sapp J.L.
      • Wells G.A.
      • Parkash R.
      • Stevenson W.G.
      • Blier L.
      • Sarrazin J.F.
      • et al.
      Ventricular tachycardia ablation versus escalation of antiarrhythmic drugs.
      ]. Drug-resistant VT is found in patients with relatively severe structural heart disease. The hypothesis that early VT ablation improves mortality and risk of hospital admission seems reasonable, but previous trials have not been sufficiently powered to assess the effect of catheter ablation on mortality [
      • Reddy V.Y.
      • Reynolds M.R.
      • Neuzil P.
      • Richardson A.W.
      • Taborsky M.
      • Jongnarangsin K.
      • et al.
      Prophylactic catheter ablation for the prevention of defibrillator therapy.
      ,
      • Kuck K.H.
      • Schaumann A.
      • Eckardt L.
      • Willems S.
      • Ventura R.
      • Delacretaz E.
      • et al.
      Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial.
      ]. Results of two recent RCTs have supported catheter ablation for prevention of sustained monomorphic VT in patients with structural heart disease [
      • Tung R.
      • Xue Y.
      • Chen M.
      • Jiang C.
      • Shatz D.Y.
      • Besser S.A.
      • et al.
      First-line catheter ablation of monomorphic ventricular tachycardia in cardiomyopathy concurrent with defibrillator implantation: the PAUSE-SCD randomized trial.
      ,
      • Della Bella P.
      • Baratto F.
      • Vergara P.
      • Bertocchi P.
      • Santamaria M.
      • Notarstefano P.
      • et al.
      Does timing of ventricular tachycardia ablation affect prognosis in patients with an implantable cardioverter Defibrillator? Results from the multicenter randomized PARTITA trial.
      ]. Importantly, these two trials included patients with NICM in addition to patients with ICM.
      The PAUSE-SCD trial [
      • Tung R.
      • Xue Y.
      • Chen M.
      • Jiang C.
      • Shatz D.Y.
      • Besser S.A.
      • et al.
      First-line catheter ablation of monomorphic ventricular tachycardia in cardiomyopathy concurrent with defibrillator implantation: the PAUSE-SCD randomized trial.
      ] aimed to determine whether catheter ablation reduces the composite endpoint of recurrent VT, cardiovascular hospitalization, and death among patients who received an ICD following spontaneous or inducible VT. A total of 133 patients were randomly allocated to ablation or standard (control) treatment. Ablation was performed within 2 days before the ICD implantation. Over a median of 31 months, the primary outcome was reduced to 45 % in the ablation group and 59 % in the control group [hazard ratio, 0.58 (95 % CI, 0.35–0.96), p = 0.035]. This difference was driven by a reduction in VT recurrence [31.7 % vs. 50.8 %, hazard ratio, 0.51 (95 % CI, 0.29–0.90)]. In contrast to the smaller PARTITA trial discussed below, there were no significant differences in mortality (8.3 % vs 6.6 %) or cardiovascular hospitalizations (28.3 % vs. 32.8 %). The trial was conducted in Asia (four centers in Japan participated), with relatively few ICM (34.7 %), NICM (30.6 %), and ARVC (34.7 %) cases. Notably, subgroup analysis revealed that, in terms of the primary endpoint, outcomes of ablation were better (though not significantly so) for patients with ARVC or ICM than for those with NICM (64.7 % vs. 50.0 %).
      The PARTITA trial [
      • Della Bella P.
      • Baratto F.
      • Vergara P.
      • Bertocchi P.
      • Santamaria M.
      • Notarstefano P.
      • et al.
      Does timing of ventricular tachycardia ablation affect prognosis in patients with an implantable cardioverter Defibrillator? Results from the multicenter randomized PARTITA trial.
      ] evaluated the effect of VT ablation on the composite endpoint of all-cause mortality or hospitalization for worsening heart failure in patients for whom therapy had not failed and were given an ICD. Patients receiving an appropriate shock after ICD implantation were allocated to ablation (n = 23) or standard treatment (n = 24), and the trial was stopped when the first interim analysis showed that the primary endpoint occurred in 1 patient in the ablation group and 10 in the standard treatment group [hazard ratio, 0.11 (95 % CI, 0.01–0.85); p = 0.034]. There were 0 deaths in the ablation group and 8 in the standard treatment group. This difference is striking and noteworthy, but the relatively low number of events requires careful consideration. Ablation significantly reduced the incidence of ICD shocks for recurrent VT (8.7 % vs. 41.7 %, p = 0.39). Although it would be tempting to assume that the reduction in arrhythmic events led to the reduction in mortality, only 3 of the 8 deaths were cardiogenic [worsening heart failure (n = 2) and cardiac arrest (n = 1)]. Therefore, the mechanism by which ablation contributed to the mortality is unclear.
      These two trials showed that prompt catheter ablation at approximately the same time as the ICD implantation or after an ICD shock reduced the recurrence of VT. If VT recurs after ICD implantation, it is reasonable to consider immediate ablation to prevent further VT in patients with ICM or ARVC if they have received shock treatment. NICM seems to be more technically challenging, and careful decision-making regarding early intervention by ablation may be warranted. Further studies are needed to clarify whether reducing VT events with ablation reduces hospitalizations and improves the survival.

      Declaration of competing interest

      Shiro Nakahara received speaker honoraria from Abbot Japan, Medtronic Japan, Biosense Webster, and Nihon Koden.

      Acknowledgments

      The author sincerely thanks Drs Yuichi Hori, Reiko Fukuda, Yuji Itabashi, Sayuki Kobayashi, Tetsuya Ishikawa, Isao Taguchi, and the staff of the Department of Cardiology at Dokkyo Medical University Saitama Medical Center for their devotion and contribution to this work.

      Funding

      This research received no grant from any funding agency in the public, commercial, or not-for-profit sectors.

      References

        • Al-Khatib S.M.
        • Stevenson W.G.
        • Ackerman M.J.
        • Bryant W.J.
        • Callans D.J.
        • Curtis A.B.
        • et al.
        2017 AHA/ACC/HRS guideline for Management of Patients with Ventricular Arrhythmias and the prevention of sudden cardiac death: executive summary: a report of the american College of Cardiology/American Heart Association task force on clinical practice guidelines and the Heart Rhythm Society.
        J Am Coll Cardiol. 2018; 72: 1677-1749
        • Epstein A.E.
        • DiMarco J.P.
        • Ellenbogen K.A.
        • Estes III, N.A.
        • Freedman R.A.
        • Gettes L.S.
        ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons.
        J. Am. Coll. Cardiol. 2008; 51: e1-e62
        • Heidenreich P.A.
        • Bozkurt B.
        • Aguilar D.
        • Allen L.A.
        • Byun J.J.
        • Colvin M.M.
        • et al.
        2022 AHA/ACC/HFSA guideline for the management of heart failure: a report of the american College of Cardiology/American Heart Association joint committee on clinical practice guidelines.
        J Am Coll Cardiol. 2022; 79: e263-e421
        • Sapp J.L.
        • Wells G.A.
        • Parkash R.
        • Stevenson W.G.
        • Blier L.
        • Sarrazin J.F.
        • et al.
        Ventricular tachycardia ablation versus escalation of antiarrhythmic drugs.
        N Engl J Med. 2016; 375: 111-121
        • Packer D.L.
        • Prutkin J.M.
        • Hellkamp A.S.
        • Mitchell L.B.
        • Bernstein R.C.
        • Wood F.
        • et al.
        Impact of implantable cardioverter-defibrillator, amiodarone, and placebo on the mode of death in stable patients with heart failure: analysis from the sudden cardiac death in heart failure trial.
        Circulation. 2009; 120: 2170-2176
        • Cronin E.M.
        • Bogun F.M.
        • Maury P.
        • Peichl P.
        • Chen M.
        • Namboodiri N.
        • et al.
        2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.
        Heart Rhythm. 2020; 17: e2-e154
        • Nogami A.
        • Kurita T.
        • Abe H.
        • Ando K.
        • Ishikawa T.
        • Imai K.
        • et al.
        JCS/JHRS 2019 guideline on non-pharmacotherapy of cardiac arrhythmias.
        Circ J. 2021; 85: 1104-1244
        • Moss A.J.
        • Hall W.J.
        • Cannom D.S.
        • Daubert J.P.
        • Higgins S.L.
        • Klein H.
        • et al.
        Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. Multicenter automatic defibrillator implantation trial investigators.
        N Engl J Med. 1996; 335: 1933-1940
        • Moss A.J.
        • Zareba W.
        • Hall W.J.
        • Klein H.
        • Wilber D.J.
        • Cannom D.S.
        • et al.
        Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction.
        N Engl J Med. 2002; 346: 877-883
        • Moss A.J.
        • Greenberg H.
        • Case R.B.
        • Zareba W.
        • Hall W.J.
        • Brown M.W.
        • et al.
        Long-term clinical course of patients after termination of ventricular tachyarrhythmia by an implanted defibrillator.
        Circulation. 2004; 110: 3760-3765
        • Mark D.B.
        • Anstrom K.J.
        • Sun J.L.
        • Clapp-Channing N.E.
        • Tsiatis A.A.
        • Davidson-Ray L.
        • et al.
        Quality of life with defibrillator therapy or amiodarone in heart failure.
        N Engl J Med. 2008; 359: 999-1008
        • Daubert J.P.
        • Zareba W.
        • Cannom D.S.
        • McNitt S.
        • Rosero S.Z.
        • Wang P.
        • et al.
        Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.
        J Am Coll Cardiol. 2008; 51: 1357-1365
        • Poole J.E.
        • Johnson G.W.
        • Hellkamp A.S.
        • Anderson J.
        • Callans D.J.
        • Raitt M.H.
        • et al.
        Prognostic importance of defibrillator shocks in patients with heart failure.
        N Engl J Med. 2008; 359: 1009-1017
        • Marchlinski F.E.
        • Haffajee C.I.
        • Beshai J.F.
        • Dickfeld T.L.
        • Gonzalez M.D.
        • Hsia H.H.
        • et al.
        Long-term success of irrigated radiofrequency catheter ablation of sustained ventricular tachycardia: post-approval THERMOCOOL VT trial.
        J Am Coll Cardiol. 2016; 67: 674-683
        • Takigawa M.
        • Frontera A.
        • Thompson N.
        • Capellino S.
        • Jais P.
        • Sacher F.
        The electrical circuit of a hemodynamically unstable and recurrent ventricular tachycardia diagnosed in 35 s with the rhythmia mapping system.
        J Arrhythm. 2017; 33: 505-507
        • Viswanathan K.
        • Mantziari L.
        • Butcher C.
        • Hodkinson E.
        • Lim E.
        • Khan H.
        • et al.
        Evaluation of a novel high-resolution mapping system for catheter ablation of ventricular arrhythmias.
        Heart Rhythm. 2017; 14: 176-183
        • Tanner H.
        • Hindricks G.
        • Volkmer M.
        • Furniss S.
        • Kuhlkamp V.
        • Lacroix D.
        • et al.
        Catheter ablation of recurrent scar-related ventricular tachycardia using electroanatomical mapping and irrigated ablation technology: results of the prospective multicenter euro-VT-study.
        J Cardiovasc Electrophysiol. 2010; 21: 47-53
        • Andreu D.
        • Penela D.
        • Acosta J.
        • Fernandez-Armenta J.
        • Perea R.J.
        • Soto-Iglesias D.
        • et al.
        Cardiac magnetic resonance-aided scar dechanneling: influence on acute and long-term outcomes.
        Heart Rhythm. 2017; 14: 1121-1128
        • Siontis K.C.
        • Kim H.M.
        • Sharaf Dabbagh G.
        • Latchamsetty R.
        • Stojanovska J.
        • Jongnarangsin K.
        • et al.
        Association of preprocedural cardiac magnetic resonance imaging with outcomes of ventricular tachycardia ablation in patients with idiopathic dilated cardiomyopathy.
        Heart Rhythm. 2017; 14: 1487-1493
        • Al-Khatib S.M.
        • Daubert J.P.
        • Anstrom K.J.
        • Daoud E.G.
        • Gonzalez M.
        • Saba S.
        • et al.
        Catheter ablation for ventricular tachycardia in patients with an implantable cardioverter defibrillator (CALYPSO) pilot trial.
        J Cardiovasc Electrophysiol. 2015; 26: 151-157
        • Reddy V.Y.
        • Reynolds M.R.
        • Neuzil P.
        • Richardson A.W.
        • Taborsky M.
        • Jongnarangsin K.
        • et al.
        Prophylactic catheter ablation for the prevention of defibrillator therapy.
        N Engl J Med. 2007; 357: 2657-2665
        • Kuck K.H.
        • Schaumann A.
        • Eckardt L.
        • Willems S.
        • Ventura R.
        • Delacretaz E.
        • et al.
        Catheter ablation of stable ventricular tachycardia before defibrillator implantation in patients with coronary heart disease (VTACH): a multicentre randomised controlled trial.
        Lancet. 2010; 375: 31-40
        • Dinov B.
        • Fiedler L.
        • Schonbauer R.
        • Bollmann A.
        • Rolf S.
        • Piorkowski C.
        • et al.
        Outcomes in catheter ablation of ventricular tachycardia in dilated nonischemic cardiomyopathy compared with ischemic cardiomyopathy: results from the prospective heart Centre of Leipzig VT (HELP-VT) study.
        Circulation. 2014; 129: 728-736
        • Tung R.
        • Vaseghi M.
        • Frankel D.S.
        • Vergara P.
        • Di Biase L.
        • Nagashima K.
        • et al.
        Freedom from recurrent ventricular tachycardia after catheter ablation is associated with improved survival in patients with structural heart disease: an international VT ablation center collaborative group study.
        Heart Rhythm. 2015; 12: 1997-2007
        • Marchlinski F.E.
        • Callans D.J.
        • Gottlieb C.D.
        • Zado E.
        Linear ablation lesions for control of unmappable ventricular tachycardia in patients with ischemic and nonischemic cardiomyopathy.
        Circulation. 2000; 101: 1288-1296
        • Mountantonakis S.E.
        • Park R.E.
        • Frankel D.S.
        • Hutchinson M.D.
        • Dixit S.
        • Cooper J.
        • et al.
        Relationship between voltage map "channels" and the location of critical isthmus sites in patients with post-infarction cardiomyopathy and ventricular tachycardia.
        J Am Coll Cardiol. 2013; 61: 2088-2095
        • Tung R.
        • Josephson M.E.
        • Bradfield J.S.
        • Shivkumar K.
        Directional influences of ventricular activation on myocardial scar characterization: voltage mapping with multiple wavefronts during ventricular tachycardia ablation.
        Circ Arrhythm Electrophysiol. 2016; 9
        • Sramko M.
        • Abdel-Kafi S.
        • van der Geest R.J.
        • de Riva M.
        • Glashan C.A.
        • Lamb H.J.
        • et al.
        New adjusted cutoffs for "Normal" endocardial voltages in patients with post-infarct LV remodeling.
        JACC Clin Electrophysiol. 2019; 5: 1115-1126
        • Aziz Z.
        • Shatz D.
        • Raiman M.
        • Upadhyay G.A.
        • Beaser A.D.
        • Besser S.A.
        • et al.
        Targeted ablation of ventricular tachycardia guided by wavefront discontinuities during sinus rhythm: a new functional substrate mapping strategy.
        Circulation. 2019; 140: 1383-1397
        • Silberbauer J.
        • Oloriz T.
        • Maccabelli G.
        • Tsiachris D.
        • Baratto F.
        • Vergara P.
        • et al.
        Noninducibility and late potential abolition: a novel combined prognostic procedural end point for catheter ablation of postinfarction ventricular tachycardia.
        Circ Arrhythm Electrophysiol. 2014; 7: 424-435
        • de Chillou C.
        • Groben L.
        • Magnin-Poull I.
        • Andronache M.
        • MagdiAbbas M.
        • Zhang N.
        • et al.
        Localizing the critical isthmus of postinfarct ventricular tachycardia: the value of pace-mapping during sinus rhythm.
        Heart Rhythm. 2014; 11: 175-181
        • Porta-Sanchez A.
        • Jackson N.
        • Lukac P.
        • Kristiansen S.B.
        • Nielsen J.M.
        • Gizurarson S.
        • et al.
        Multicenter study of ischemic ventricular tachycardia ablation with decrement-evoked potential (DEEP) mapping with extra stimulus.
        JACC Clin Electrophysiol. 2018; 4: 307-315
        • Jais P.
        • Maury P.
        • Khairy P.
        • Sacher F.
        • Nault I.
        • Komatsu Y.
        • et al.
        Elimination of local abnormal ventricular activities: a new end point for substrate modification in patients with scar-related ventricular tachycardia.
        Circulation. 2012; 125: 2184-2196
        • Tung R.
        • Raiman M.
        • Liao H.
        • Zhan X.
        • Chung F.P.
        • Nagel R.
        • et al.
        Simultaneous endocardial and epicardial delineation of 3D reentrant ventricular tachycardia.
        J Am Coll Cardiol. 2020; 75: 884-897
        • Graham A.J.
        • Orini M.
        • Zacur E.
        • Dhillon G.
        • Daw H.
        • Srinivasan N.T.
        • et al.
        Simultaneous comparison of electrocardiographic imaging and epicardial contact mapping in structural heart disease.
        Circ Arrhythm Electrophysiol. 2019; 12e007120
        • Deno D.C.
        • Balachandran R.
        • Morgan D.
        • Ahmad F.
        • Masse S.
        • Nanthakumar K.
        Orientation-independent catheter-based characterization of myocardial activation.
        IEEE Trans Biomed Eng. 2017; 64: 1067-1077
        • Tavares L.
        • Lador A.
        • Fuentes S.
        • Da-Wariboko A.
        • Blaszyk K.
        • Malaczynska-Rajpold K.
        • et al.
        Intramural venous ethanol infusion for refractory ventricular arrhythmias: outcomes of a multicenter experience.
        JACC Clin Electrophysiol. 2020; 6: 1420-1431
        • Blanck O.
        • Bode F.
        • Gebhard M.
        • Hunold P.
        • Brandt S.
        • Bruder R.
        • et al.
        Dose-escalation study for cardiac radiosurgery in a porcine model.
        Int J Radiat Oncol Biol Phys. 2014; 89: 590-598
        • Cuculich P.S.
        • Schill M.R.
        • Kashani R.
        • Mutic S.
        • Lang A.
        • Cooper D.
        • et al.
        Noninvasive cardiac radiation for ablation of ventricular tachycardia.
        N Engl J Med. 2017; 377: 2325-2336
        • Samuel M.
        • Elsokkari I.
        • Sapp J.L.
        Ventricular tachycardia burden and mortality: association or Causality?.
        Can J Cardiol. 2022; 38: 454-464
        • Tung R.
        • Xue Y.
        • Chen M.
        • Jiang C.
        • Shatz D.Y.
        • Besser S.A.
        • et al.
        First-line catheter ablation of monomorphic ventricular tachycardia in cardiomyopathy concurrent with defibrillator implantation: the PAUSE-SCD randomized trial.
        Circulation. 2022; 145: 1839-1849
        • Della Bella P.
        • Baratto F.
        • Vergara P.
        • Bertocchi P.
        • Santamaria M.
        • Notarstefano P.
        • et al.
        Does timing of ventricular tachycardia ablation affect prognosis in patients with an implantable cardioverter Defibrillator? Results from the multicenter randomized PARTITA trial.
        Circulation. 2022; 145: 1829-1838