Author + information
- Thomas Deneke, MDa,b,∗ (, )
- Andreas Mügge, MDb,
- Elena Ene, MDa,
- Karin Nentwich, MDa and
- Philipp Halbfaß, MDa
- aClinic for Interventional Electrophysiology, Heart Center Bad Neustadt, Bad Neustadt, Germany
- bDepartment of Cardiology, Heart Center Bermgannsheil, Ruhr-University Bochum, Bochum, Germany
- ↵∗Address for correspondence:
Prof. Dr. Thomas Deneke, Clinic for Interventional Electrophysiology, Heart Center Bad Neustadt, Salzburger Leite 1, GER 97616 Bad Neustadt, Germany.
Catheter ablation of ventricular tachycardia (VT) has beneficial effects on arrhythmia recurrences, electrical storm, and rehospitalization in an ischemic cardiomyopathy (ICM) population, but data on ablation of nonischemic cardiomyopathy (NICM) etiology of structural VT is sparse. Reports are limited to a small group of highly experienced centers. Recent studies document a lower efficacy of VT ablation in NICM patients compared with in ICM patients, and recurrences are significantly more often in NICM patients (1–4). One of the reasons is that whereas the mechanism of VT in ICM appears well understood, the substrate and therefore also the mechanism of VT is more complex in NICM. So far, no study comparing outcome of NICM-VT ablation to other treatment modalities is available, and therefore ablation of VT in the general population of NICM is recommended in the guidelines as “may be considered” after failure of antiarrhythmic medication (usually amiodarone). In specialized centers, the NICM population approaches one-half of the patients undergoing ablation for structural VT, but ablation approaches, treatment strategies, and endpoints of interventional therapy remain widely heterogeneous. In addition, the group of NICM encompasses a heterogeneous group of cardiac pathologies, and further subdivision may be necessary for optimized treatment, but subdividing an already small group of patients may lead to inadequate power of subgroup analysis (2,3).
In this issue of JACC: Clinical Electrophysiology, Vaseghi et al. (5) increase evidence on the efficacy of catheter ablation in different subsets of NICM pathologies gathered in a combined effort of the IVTCC (International Ventricular Tachycardia Ablation Center Collaborative) experience. It is the seventh publication by the IVTCC group and focuses on VT ablation in NICM. The overall group of 780 patients consisted of 6 different subsets of NICM pathologies including dilated cardiomyopathy (DICM) as the largest group in 518 patients, right ventricular cardiomyopathy (ARVC) in 100 patients, valvular CM and myocarditis in 50 patients each, hypertrophic CM in 35 patients, and sarcoidosis in 27 patients. Of note, although 12 of the most renowned and largest VT ablation expert centers have combined their experience on the largest so far published group of NICM-VT ablations, only a mean of 5.4 NICM-VT ablations per year per center were included, indicating the sparsity of experience. Twelve-month freedom from any ventricular arrhythmia during follow-up was 69% in the overall group being lower than the experience published by the IVTCC group on ICM (72%) (1).
The study is in line with previous publications on NICM-VT ablation experience and overall results are comparable (freedom from VT recurrence achieved in 77% in a comparable mix of NICM patient subgroups) although it remains unclear how many previously published patients from different groups are included in the current IVTCC report (2,3). Outcome of VT ablation was worst in hypertrophic, valvular, and sarcoid subtypes. In addition to NICM- subtype, lower left ventricular ejection fraction, higher New York Heart Association functional class, and number of induced VT were predictors of VT recurrence. All these parameters indicate lower efficacy in a more severe left ventricular pathology. Three main aspects are covered that merit further discussion.
Technical and Procedural Aspects of VT Ablation in NICM
Efficacy of catheter ablation is related to the understanding of the underlying substrate and the potential to target scar tissue relevant to the VT mechanism. Therefore, differences in outcome depend on the strategy of mapping and ablating the underlying scar pathology. Different subtypes of NICM therefore need different approaches for effective VT treatment.
Details about the procedures are not documented in the report by Vaseghi et al. (5) but may include the need for high-density multi-microelectrode catheter mapping and a need for epicardial ablation as well as definition of endpoints such as effective late potential abolition and noninducibility testing. Whereas programmed ventricular stimulation to induce VT is limited by many aspects such as prior noninducibility, deferral of testing after ablation and variable reproducibility of programmed ventricular stimulation noninducibility of any VT has been shown to predict superior freedom from ventricular arrhythmia recurrences and mortality (6). Post-procedural noninvasive programmed ventricular stimulation as test for inducibility of VT days after ablation is also predictive of future recurrences (7) in ICM and NICM. Implementing noninvasive programmed stimulation into the strategy of NICM-VT ablation may help to identify patients in need of early redo procedures, to appropriately program implantable cardioverter-defibrillators, and to risk-stratify patients potentially for future need of implantable cardioverter-defibrillators.
Approximately 40% of the procedures included epicardial instrumentation without differences among the 6 different NICM subtypes. Epicardial ablation is performed to increase efficacy of VT ablation and combined endocardial and epicardial approaches have been linked to higher long-term efficacy specifically in ARVC patients and in nonseptal DICM scar substrates. In the study by Vaseghi et al. (5) epicardial ablation was not related to higher efficacy or better outcome. It remains unclear whether any of the subtypes may benefit from primary endocardial-epicardial approaches.
Differentiation of NICM subsets by location and topography of scar tissue (e.g., septal vs. nonseptal topology) may be a helpful additional discriminator to predict outcome and help to understand some of the reasons for lower ablation efficacy in subsets of NICM. In addition, definition of NICM subsets is not exclusive and overlaps and misdiagnosis may occur. Pre-ablation imaging (mostly cardiac magnetic resonance tomography) has been helpful in documenting scar areas and target sites for VT ablation and is specifically relevant in NICM as a helpful tool for pre-ablation procedural planning including need for epicardial access and focusing on specific target areas. Performing cardiac magnetic resonance tomography should be considered in all patients with NICM before undergoing implantable cardioverter-defibrillator implantation.
High-density micro-multielectrode mapping has helped to identify low voltage and electrogram abnormalities to a much higher extent than limited ablation catheter maps can. Especially for mapping less-well known scar VT and characterizing the underlying scar pathology, high-density mapping of the underlying electrophysiological substrate is of particular value. Whereas these catheters have been implemented in clinical practice, the effect on outcome of VT ablation remains unclear.
Optimum mapping strategies, need for epicardial access, ablation settings, and strategy, as well as endpoints and evaluation have to be defined to individualize mapping and ablation strategies within an overall standardized approach for subgroups of patients. Vaseghi et al. (5) clarify that understanding the underlying pathology is key to effective VT ablation and specifically valvular, hypertrophic, and sarcoid CM are at increased risk for failure to long-term VT suppression.
An interesting point of the study by Vaseghi et al. (5) is that despite the complexity of the procedures, NICM-VT complications are low (7%) and not higher than in ICM-VT ablations. Ablation of NICM-VT should be performed primarily by high expertise operators at dedicated, specialized centers, creating high efficacy and superior safety profiles. To further increase efficacy and understanding of the underlying pathology NICM-VT, ablation procedures may be focused in some highly experienced VT ablation centers.
Predictors of Ventricular Arrhythmia Recurrence
Approximately 30% of patients experienced VT recurrence within 12 months in the study by Vaseghi et al. (5). Subgroup analysis revealed better outcome of VT ablation in DICM, ARVC, and myocarditis, whereas efficacy of ablation was worst in valvular CM and sarcoidosis with almost 50% VT recurrences within the first year. It is important to know that outcome of VT in valvular and hypertrophic CM as well as cardiac sarcoidosis has a poor prognosis in regard to VT freedom. This should be taken into account when considering these patients for ablation and additional antiarrhythmic medical treatment may be needed.
It is interesting to see, that in the group of NICM patients, VT ablation also was less effective in the smaller subgroups and most effective in the largest cohorts of DICM and ARVC. In multivariate analysis, hypertrophic CM, valvular myopathy, and sarcoidosis appear as independent predictors of VT recurrence almost doubling the risk for recurrent VT during follow-up. Most likely, the lower efficacy in hypertrophic CM, valvular CM, and sarcoidosis is an indicator for the missing in-depth understanding of the VT mechanism added to hard-to-ablate (potentially intramural) targets. In addition to insufficient ablation, disease progression during follow-up appears to be relevant for ablation outcome, as well.
The optimum time point for ablation of VT still remains under debate. Vaseghi et al. (5) indicate that a history of VT ablation and the use of 2 or more prior antiarrhythmic drugs predict VT recurrences. A prior study indicated a “the earlier the better” finding with early VT ablation having superior success rates compared with those of ablation performed late after first documentation of VT (8). Although VT ablation is recommended in patients after failed antiarrhythmic medication integrating catheter ablation into an early phase, the treatment strategy for structural VT may lead to better outcome of ablation in NICM. Ineffective prior VT ablation was documented in over 40% of patients in reports from expert tertiary referral centers (2,5), indicating the differences in outcome from expert centers to less-experienced VT ablation groups and the need for top-level ablation programs for effective treatment of NICM VT.
Predictors of Death in NICM-VT Patients
Although VT recurrence has been linked to higher mortality and catheter ablation to lower recurrences of VT, randomized controlled trials failed to show a beneficial effect of VT ablation on mortality. This was documented in a paper by the IVTCC group that indicated a significantly lower transplant-free survival if VT recurred after ablation (1). At a median follow-up of 13 months, 18% of patients died and 6% underwent cardiac transplantation as documented in the present study (5), over 40% of patients who reached this endpoint did not have VT recurrence. One aspect that is not well addressed in many VT-ablation trials is the need for an interdisciplinary approach to these patients with structural heart disease and ventricular arrhythmias. Optimal heart failure management is crucial because death is usually not arrhythmogenic but rather due to progression of the underlying heart disease and heart failure decompensations (6,7,9,10).
There is the need for a multimodality approach to these patients including, in addition to interventional electrophysiologists, interventional cardiologists, heart failure and device specialists, and cardiac surgeons if assist devices may be needed. A VT network establishing logistics for easy transfer of patients into VT units in centers capable of doing complex endocardial and epicardial VT ablation has been shown beneficial in electrical storm patients (9) and should be expanded to all NICM-structural-VT patients.
The presented IVTCC study helps to understand differences of VT ablation efficacy in NICM subgroups and implicates that NICM-VT should be ablated primarily in highly experienced centers with a specialized logistics for early referral and ablation in addition to a multimodality team approach. Efficacy depends on the NICM pathology and most likely on scar topology, distribution, and biology. An important determinant of mortality outcome in addition to effective VT ablation maybe appropriate heart failure management.
Vaseghi et al. (5) are to be congratulated for their effort to help understand differences in VT ablation outcome in the complex group of NICM patients. Future studies need to help elaborate individually tailored but standardized decisive mapping and ablation strategies by taking into consideration the specific NICM subtype and testing these protocols for relevance to outcome.
↵∗ Editorials published in JACC: Clinical Electrophysiology reflect the views of the authors and do not necessarily represent the views of JACC: Clinical Electrophysiology or the American College of Cardiology.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose. Katja Zeppenfeld, MD, served as the Guest Editor for this article.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- 2018 American College of Cardiology Foundation
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