| CHAPTER | ||
| 36 | Epicardial Catheter Ablation of Ventricular Tachycardia: A Meta-Analysis | |
| Rhanderson Cardoso, MD; Fabrizio R. Assis, MD; André d’Avila, MD, PhD |
INTRODUCTION
Patients with structural heart disease are at increased risk for developing ventricular tachyarrhythmias due to scar-related reentry circuits. Though implantable cardioverter-defibrillators (ICDs) reduce mortality in patients with a history of aborted sudden cardiac death (SCD), sustained ventricular tachycardia (VT), and in selected primary prevention patients, recurrent ICD therapies can impair quality of life and increase mortality.1–4
Percutaneous catheter ablation has been established as a therapeutic alternative in selected patients with a history of ventricular arrhythmias, particularly if recurrent or requiring ICD shocks. Among patients with a history of ischemic cardiomyopathy and VT despite the use of anti-arrhythmic drugs (AADs), the combined endpoint of death, VT storm, or appropriate ICD shock is reduced by nearly 30% with catheter ablation as compared to escalation of drug therapy.5
The efficacy of an endocardial approach to VT ablation is limited by the presence of intramural or epicardial arrhythmia substrates. Epicardial access for mapping and ablation can be used in such cases. Though clinical, electrocardiographic, and imaging characteristics can help to identify patients with epicardial scar, there is no established consensus with regard to patient selection for epicardial ablation and whether epicardial access should be performed up front or only after failure of an endocardial attempt.
Therefore, we performed a meta-analysis of studies comparing a strategy of an epicardial approach, with or without endocardial access (henceforth called endo-epicardial) versus endocardial-only access for mapping and catheter ablation of VT, including ischemic and nonischemic substrates.
MATERIAL AND METHODS
Eligibility Criteria
Inclusion in this meta-analysis was restricted to studies that met all the following eligibility criteria: (1) randomized trials or nonrandomized cohorts; (2) comparing an endo-epicardial approach to endocardial-only mapping and ablation; and (3) reporting any of the outcomes of interest. We also excluded studies with no control group and those restricted to patients with idiopathic ventricular arrhythmias without structural heart disease.
Search Strategy and Data Extraction
We systematically searched PubMed, Scopus, and the Cochrane Central Register of Controlled Trials from inception to October 2018 with the following medical subject heading terms: endocardial, epicardial, ventricular tachycardia, and ablation. We reviewed the references from studies selected for inclusion for any additional studies that were potentially missed by the search in databases.
Endpoints and Subanalyses
Efficacy outcomes included VT inducibility at end-procedure, VT inducibility of the clinical tachycardia at end-procedure, a composite of VT recurrence or appropriate ICD therapies, and all-cause mortality. Given that both groups underwent endocardial catheter ablation, safety events were undoubtedly increased in the endoepicardial group due to the addition of epicardial access. Reviews of safety outcomes from epicardial access for mapping and catheter ablation have been reported separately and are not discussed in this meta-analysis.6–8
Our study followed the Cochrane Collaboration PRISMA recommendations for conduction and reporting of systematic reviews and meta-analyses (Figure 36.1).9 Odds-ratios (OR) with 95% confidence intervals were computed for binary endpoints. There were no continuous outcomes. Heterogeneity was assessed with Cochran’s Q test and I2 statistics. If significant heterogeneity was identified (I2 > 25%), we used a DerSimonian and Laird random-effects model. Otherwise, a fixed-effect model was applied. Review Manager 5.3 (Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark) was used for statistical analysis.
Figure 36.1 PRISMA flow diagram of study screening and selection.
RESULTS
Study Selection and Characteristics
The search strategy yielded 2457 results. After removal of duplicates and studies not related to the topic of interest based on title and abstract, 47 studies were fully reviewed for inclusion and exclusion criteria. Of these, an additional 25 studies did not have a control group or did not report outcomes of interest. Therefore, a total of 22 studies were included in the meta-analysis. The pooled number of procedures was 1138, of which 500 (44%) were performed with epicardial access for mapping and/or ablation, the majority of which underwent concomitant endocardial ablation (> 90%). Approximately 56% of patients underwent endocardial ablation exclusively. Study and procedural characteristics are outlined in Tables 36.1 and 36.2, respectively.
Table 36.1 Study Characteristics
Abbreviations: ARVC, arrhythmogenic right ventricular cardiomyopathy; HCMP, hypertrophic cardiomyopathy; ICD, implantable cardioverter-defibrillator; ICMP, ischemic cardiomyopathy; NA, not available or not applicable; NICMP, nonischemic cardiomyopathy.
Table 36.2 Procedural Characteristics
Abbreviations: CI, critical isthmus; CL, cycle length; LP, late potentials; NA, not available or not applicable; VT, ventricular tachycardia.
Pooled Analysis of All Studies
In studies that used programmed ventricular stimulation to induce VT after ablation, inducibility of the clinical tachycardia (OR 1.52; 95% CI [0.79–2.92]; P = 0.21; I2 = 0%) and of any VT (OR 1.04; 95% CI [0.61–1.76]; P = 0.90; I2 = 37%) was not significantly different between groups. During a wide spectrum of follow-up duration, which ranged from 7–70 months in different studies, the composite outcome of VT recurrence or appropriate ICD therapies was significantly reduced in patients who received endo-epicardial (113/357; 31.6%) versus endocardial (243/508; 47.8%) ablation (OR 0.52; 95% CI [0.39–0.71]; P < 0.01; I2 = 10%; Figure 36.2, Panel A). There was also a significantly lower all-cause mortality in the endo-epicardial group (14/219; 6.4%) as compared to endocardial-only (46/353; 123%) ablation (OR 0.50; 95% CI [0.27–0.94]; P = 0.03; I2 = 0%; Figure 36.2, Panel B).
Figure 36.2 Panel A: VT recurrence or appropriate ICD therapy was significantly lower in the epicardial group (OR 0.52; P < 0.01). Panel B: All-cause mortality was significantly lower in the epicardial group (OR 0.50; P = 0.03).
Among 9 studies involving 271 patients with nonischemic cardiomyopathies, VT inducibility was not significantly different between the endo-epicardial ablation and endocardial-only ablation groups (OR 1.1; 95% CI [0.48–2.52]; P = 0.81; I2 = 40%). The incidence of VT recurrence or appropriate ICD therapies during follow-up was also similar between groups (OR 0.70; 95% CI [0.41–1.21]; P = 0.20; I2 = 0%; Figure 36.3, Panel A). All-cause mortality was similar between the endo-epicardial group (13.6%) and the endocardial-only group (20%; OR 0.57; 95% CI [0.20–1.64]; P = 0.30; I2 = 0%; Figure 36.3, Panel B).
Figure 36.3 Panel A: VT recurrence or appropriate ICD therapy was not significantly different between groups in patients with nonischemic cardiomyopathies (OR 0.70; P = 0.20). Panel B: All-cause mortality was not significantly different between groups in patients with nonischemic cardiomyopathies (OR 0.57; P = 0.30).
In 6 studies including 323 patients with ischemic cardiomyopathy, VT inducibility was not significantly different between groups (OR 1.04; 95% CI [0.56–1.95]; P = 0.90; I2
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