Catheter Ablation of Ventricular Tachycardia in Nonischemic Dilated Cardiomyopathy

HomeCirculation: Arrhythmia and ElectrophysiologyVol. 9, No. 10Catheter Ablation of Ventricular Tachycardia in Nonischemic Dilated Cardiomyopathy Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBCatheter Ablation of Ventricular Tachycardia in Nonischemic Dilated CardiomyopathyA Difficult Field Where We Should Focus Our Efforts Paolo Della Bella, MD and Nicola Trevisi, MD Paolo Della BellaPaolo Della Bella From the Arrhythmia Unit and Electrophysiology Laboratories, Department of Cardiology and Cardiothoracic Surgery, Ospedale San Raffaele, Milan, Italy. and Nicola TrevisiNicola Trevisi From the Arrhythmia Unit and Electrophysiology Laboratories, Department of Cardiology and Cardiothoracic Surgery, Ospedale San Raffaele, Milan, Italy. Originally published12 Oct 2016https://doi.org/10.1161/CIRCEP.116.004649Circulation: Arrhythmia and Electrophysiology. 2016;9:e004649Ablation of ventricular tachycardia (VT) is being increasingly recognized as an important treatment option in patients with structural heart disease and recurrent arrhythmias leading to frequent implantable cardioverter-defibrillator shocks. Recent multicenter studies1 have shown the association between successful ablation, prevention of arrhythmia recurrences, and prolonged survival.See Article by Muser et alThe initial concepts guiding mapping and ablation and the early clinical experiences were mostly focused on postinfarct VT in the setting of ischemic cardiomyopathy; the incidence of VT related to nonischemic etiologies is growing, accounting for over half of the VT ablation patient population in many tertiary referral ablation centers. Nonischemic VTs arise in the setting of a heterogeneous group of disease entities, related to different arrhythmia mechanisms and substrates, with markedly variable acute outcomes and also different long-term clinical implications.2 Although many studies have reported on VT ablation performed in mixed populations, it is important to acquire outcome and complication data derived from specific subgroup of patients to help develop appropriate indications.Ablation treatment of VT in idiopathic dilated nonischemic cardiomyopathy (IDCM) is actually an emerging need because the reduction of sudden death by implantable cardioverter-defibrillator allows the progression of the natural history of the disease. Frequent VT recurrences and electrical storm in this clinical setting carry severe prognostic implications, and the efficacy of antiarrhythmic drug treatment is low. Reported outcomes of ablation are generally worse than those achieved in postinfarct VTs,2 and the mapping/ablation procedure is particularly challenging because of the less well-defined arrhythmia substrate (patchy or diffuse microscarring process) and the frequent intramural or subepicardial location of areas acting as the isthmus of slow conduction that are usually targeted for the ablation. Strategies for sinus rhythm–based substrate modification are less easily applicable in this setting because of the paucity of abnormal activity recorded at the endo- or epicardial substrate, and frequent activation/entrainment mapping strategies are of limited use because of the hemodynamic intolerance to induced VTs frequently encountered in this group of patients.3 Furthermore, concurrent comorbidities frequently add to the risk of complications.Under this perspective, the favorable experience reported by Muser et al4 offers an important information. The authors investigated on a population of 282 patients from 1999 to 2014, undergoing VT ablation for IDCM. The VT-free survival was ≈70% at 5 years, and, among those who experienced arrhythmia recurrences, ablation resulted in a significant decrease in the arrhythmia burden. It is important to appreciate that other nonischemic disease etiologies, such as arrhythmogenic right ventricular cardiomyopathy, hypertrophic cardiomyopathy, repaired congenital heart disease, or others, likely to contaminate the results with more or less favorable outcomes, were not included.When Is Epicardial Mapping and Ablation Indicated?According to this experience, the majority of the procedures can be effectively accomplished by an endocardial approach only, as it had been undertaken in 38% of the procedures and actually used for the subsequent epicardial ablation in 27%; it means that even in this setting, there is not an uniform need to proceed epicardially and that a variety of criteria, beyond a previous failure, can be used to direct the ablation, including preoperative imaging and, more practically, salient endocardial mapping features, such as the finding of unipolar voltage abnormalities during sinus rhythm. Although in selected cases of free wall location, epicardial mapping is rewarding by disclosing critical areas of abnormal electric activity linked to the arrhythmia mechanism, the possibility of performing the ablation safely is limited by the course of the epicardial coronary arteries. Ablation over a coronary artery is impossible because of the risk for acute occlusion or later intimal proliferation leading to vessel stenosis or occlusion. The electric capture of the left phrenic nerve over the area of intended ablation indicates high likelihood of permanent damage leading to diaphragmatic palsy, thereby preventing the safe accomplishment of the procedure, unless physical maneuvers are undertaken to attempt the displacement of the nerve; however, this may, not always be achieved. It is, therefore, no wonder that, after the identification of a suitable epicardial target, the ablation might not be accomplished, as evidenced by the reported experience. The low but definite incidence of serious side effects related to the epicardial access maneuvers (3% of the study population), even in the hands of an experienced group of operators, confirms the suggestion for a cautious attitude, where epicardial approach would be indicated on solid arguments. This point is of practical relevance as, after the initial mapping studies,5 the need for epicardial access was perceived as an almost uniform requirement to achieve VT ablation in the setting of IDCM. It seems now well established that an epicardial attempt might be considered only where a free wall location of the scar6 would allow the identification of proper ablation targets epicardially.It is a good practice to perform cardiac magnetic resonance preoperative scans to guide the decision to a first-line epicardial approach when indicated because this form of imaging is likely to identify the epicardial extension of scarred tissue. The 12-lead surface ECG morphology during VT may provide some important clues as to a possible epicardial origin of the arrhythmia, but it is limited by the availability of suitable tracings during ongoing arrhythmia, particularly among patients where the implantable cardioverter-defibrillator provides prompt arrhythmia termination; some indirect evidence of a left free wall location may be obtained by the analysis of the baseline sinus or paced rhythm 12-lead ECG, as recently suggested by Oloriz et al.7 In their experience on 89 patients with IDCM undergoing extensive endo- and epicardial mapping before ablation, the finding of any atrioventricular conduction disturbance, including first-degree atrioventricular block or higher, left bundle branch block or proven pacing dependency, was strongly related to a septal location of the scarring process and to a low yield of epicardial targets at the subsequent ablation.Limitations of Our Currently Used ToolsThe septal location of the scar,8 in addition to its negative prognostic value as an indicator of disease progression among IDCM patients, is the main hurdle and the leading cause for failure of ablation, as reported in the present, as well as in other published, series.The limited lesion depth achievable even by high-power irrigated radiofrequency may prevent complete ablation of deep substrates, both at the basal septum and at the basal anterior left ventricular (LV) wall, the 2 preferential sites of scarring in IDCM. A septal location of the target area accounted for one third of the present cohort: in this setting, in addition to prolonged high-power radiofrequency pulses on the left septum, the delivery of sequential unipolar right and left septal lesions is the only currently available practical option, but it frequently fails; to this point, active research is being performed investigating the concept of bipolar radiofrequency ablation or even delivering radiofrequency current intramurally via a needle electrode catheter.9 Reported results are promising, but larger clinical trials are needed. The basal anterior wall of the left ventricle is another critical site where the traditional ablation is limited,10 due to the thickness of the myocardium that may exceed 15 mm; the epicardial approach to this region, therefore, named as the inaccessible LV summit, is limited by the epicardial fat layer and the course of the left main or proximal left anterior descending coronary artery. Attempts at ablation from within the great cardiac vein or the coronary cusps are frequently reported, as in this series, but the efficacy is low. The possibility of a direct open chest surgical epicardial cryoablation11 to treat deep substrates located in the anterior basal region of the left ventricle (inaccessible LV summit) has opened the way to treat percutaneous ablation failures and should be considered an option offered by highly specialized centers. The possibility to develop epicardial cryoablation approaches with limited exposure might represent an interesting option worth investigating in the future.Can We Predict Outcome in This Specific Patient Population?The inducibility of sustained VT at the programmed stimulation study performed at the end of the procedure, and even more, at the noninvasive programmed stimulation performed 2 to 4 days after, was strong predictor of arrhythmia recurrence.12 In view of its high positive predictive value, the practice of delayed programmed stimulation via the implantable cardioverter-defibrillator (noninvasive programmed stimulation), which is routine at the investigator's center and now at few others, could be attractive by setting the stage for more complex nonstandard redo procedures, including epicardial or, possibly cryosurgical, interventions, where proper planning is critical.Prognosis in Relation to Cardiac Function and Timing of the ProcedureThe association between poor LV function and recurrent VT after ablation is confirmed in the current series; patients with an LV ejection fraction <35% had a significantly higher VT recurrence rate and, in turn, higher mortality and transplant rates at follow-up. Conversely, about half of the study population had LV ejection fraction values >35%. It might be interesting to understand whether and why different scarring patterns are linked to different prognosis, in an attempt to stratify timing and indications to intervention. The observation that patients with a clinical or biopsy-proven diagnosis of remote myocarditis, even at different extents of cardiac involvement, tend to have similar topographical patterns of scarring, mostly occurring at the inferior or lateral free wall, suggest a possible further subdivision of IDCM patients into subgroups with specific arrhythmia substrates and related mapping strategies.Also, timing of the ablation procedure is an important issue that should be specifically investigated in patients with IDCM, where the load of comorbidities may further decrease the tolerability to recurrent arrhythmias. Under this perspective, the careful analysis performed in the long-term prescription of antiarrhythmic drug after the ablation provides important information. The percentage of patients in long-term treatment with amiodarone dropped from 59% (before the ablation) to 22% at last follow-up available, with an average daily dose slightly >200 mg. As recently documented by the VANISH study (Ventricular Tachycardia Ablation Versus Escalation of Antiarrhythmic Drugs),13 the incidence of serious side effects is strongly correlated with the long-term usage of antiarrhythmic drugs and mainly related to the long-term extracardiac toxicity of amiodarone. The experience offered by the authors supports the effective antiarrhythmic adjuvant role of catheter ablation, leading to an overall decreased utilization of the drug in IDCM patients experiencing recurrent VT. In this perspective, an earlier intervention timing, even if its impact on the evolution of underlying heart disease is not demonstrated, by limiting the exposure to potentially deleterious drug side effects, may contribute to an improved quality of life if not to enhance life expectancy.Despite the current technical challenges and the sometimes frustrating outcomes, the ablation of VT in IDCM is an important option to be included in the program of each important electrophysiology center offering ablation treatment for VT.Technical and clinical research in this specific field should be encouraged to overcome the present limitations in this important area.DisclosuresDr Della Bella is a consultant for St Jude Medical and Boston Scientific, and has received research grants from Biosense, St Jude Medical, Biotronik, and Boston Scientific. The other author has no disclosures to report.FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.Correspondence to Paolo Della Bella, MD, Arrhythmia Unit and Electrophysiology Laboratories, Ospedale San Raffaele, via Olgettina 60, Milan 20132, Italy. E-mail [email protected]References1. Tung R, Vaseghi M, Frankel DS, Vergara P, Di Biase L, Nagashima K, Yu R, Vangala S, Tseng CH, Choi EK, Khurshid S, Patel M, Mathuria N, Nakahara S, Tzou WS, Sauer WH, Vakil K, Tedrow U, Burkhardt JD, Tholakanahalli VN, Saliaris A, Dickfeld T, Weiss JP, Bunch TJ, Reddy M, Kanmanthareddy A, Callans DJ, Lakkireddy D, Natale A, Marchlinski F, Stevenson WG, Della Bella P, Shivkumar K. 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Muresan L, Cismaru G, Martins R, Bataglia A, Rosu R, Puiu M, Gusetu G, Mada R, Muresan C, Ispas D, Le Bouar R, Diene L, Rugina E, Levy J, Klein C, Sellal J, Poull I, Laurent G and de Chillou C (2019) Recommendations for the use of electrophysiological study: Update 2018, Hellenic Journal of Cardiology, 10.1016/j.hjc.2018.09.002, 60:2, (82-100), Online publication date: 1-Mar-2019. Dilaveris P, Antoniou C and Gatzoulis K (2017) Arrhythmic risk stratification in non-ischemic dilated cardiomyopathy: Where do we stand after DANISH?, Trends in Cardiovascular Medicine, 10.1016/j.tcm.2017.06.003, 27:8, (542-555), Online publication date: 1-Nov-2017. October 2016Vol 9, Issue 10 Advertisement Article InformationMetrics © 2016 American Heart Association, Inc.https://doi.org/10.1161/CIRCEP.116.004649PMID: 27733498 Originally publishedOctober 12, 2016 Keywordstachycardia, ventricularcardiomyopathy, dilatedcomorbiditycatheter ablationidiopathic dilated cardiomyopathyEditorialsPDF download Advertisement SubjectsArrhythmiasCatheter Ablation and Implantable Cardioverter-Defibrillator