Background—: Ventricular tachycardia (VT) substrate ablation usually requires extensive ablation. Scar dechanneling technique may limit the extent of ablation needed. Methods and Results—: The study included 101 consecutive patients with left ventricular scar–related VT (75 ischemic patients; left ventricular ejection fraction, 36±13%). Procedural end point was the elimination of all identified conducting channels (CCs) by ablation at the CC entrance followed by abolition of residual inducible VTs. By itself, scar dechanneling rendered noninducibility in 54.5% of patients; ablation of residual inducible VT increased noninducibility to 78.2%. Patients needing only scar dechanneling had a shorter procedure (213±64 versus 244±71 minutes; P =0.027), fewer radiofrequency applications (19±11% versus 27±18%; P =0.01), and external cardioversion/defibrillation shocks (20% versus 65.2%; P <0.001). At 2 years, patients needing scar dechanneling alone had better event-free survival (80% versus 62%) and lower mortality (5% versus 11%). Incomplete CC-electrogram elimination was the only independent predictor (hazard ratio, 2.54 [1.06–6.10]) for the primary end point. Higher end point-free survival rates were observed in patients noninducible after scar dechanneling (log-rank P =0.013) and those with complete CC-electrogram elimination (log-rank P =0.013). The complications rate was 6.9%, with no deaths. Conclusions—: Scar dechanneling alone results in low recurrence and mortality rates in more than half of patients despite the limited ablation extent required. Residual inducible VT ablation improves acute results, but patients who require it have worse outcomes. Recurrences are mainly related to incomplete CC-electrogram elimination.

Background—: Conducting channels are the target for ventricular tachycardia (VT) ablation. Conducting channels could be identified with contrast enhanced–cardiac magnetic resonance (ce-CMR) as border zone (BZ) corridors. A 3-dimensional (3D) reconstruction of the ce-CMR could allow visualization of the 3D structure of these BZ channels. Methods and Results—: We included 21 patients with healed myocardial infarction and VT. A 3D high-resolution 3T ce-CMR was performed before CARTO-guided VT ablation. The left ventricular wall was segmented and characterized using a pixel signal intensity algorithm at 5 layers (endocardium, 25%, 50%, 75%, epicardium). A 3D color-coded shell map was obtained for each layer to depict the scar core and BZ distribution. The presence/characteristics of BZ channels were registered for each layer. Scar area decreased progressively from endocardium to epicardium (scar area/left ventricular area: 34.0±17.4% at endocardium, 24.1±14.7% at 25%, 16.3±12.1% at 50%, 13.1±10.4 at 75%, 12.1±9.3% at epicardium; P <0.01). Forty-five BZ channels (2.1±1.0 per patient, 23.7±12.0 mm length, mean minimum width 2.5±1.5 mm) were identified, 85% between the endocardium and 50% shell and 76% present in ≥1 layer. The ce-CMR–defined BZ channels identified 74% of the critical isthmus of clinical VTs and 50% of all the conducting channels identified in electroanatomic maps. Conclusions—: Scar area in patients with healed myocardial infarction decreases from the endocardium to the epicardium. BZ channels, more commonly seen in the endocardium, display a 3D structure within the myocardial wall that can be depicted with ce-CMR. The use of ce-CMR–derived maps to guide VT ablation warrants further investigation.

Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) provides tissue characterization of ventricular myocardium and scar that can be depicted as pixel signal intensity (PSI) maps. To assess the possible benefit of guiding the ventricular tachycardia (VT) substrate mapping by integrating these PSI maps into the navigation system. In total, 159 consecutive patients (66 ± 11 years old, 151 men [95%]) with scar-related left ventricular (LV) VT were included. VT substrate ablation used the scar dechanneling technique. A CMR-aided ablation using the PSI maps was performed in 54 patients (34%). Procedural data as well as acute and long-term outcomes were compared with those of the remaining 105 patients (66%). Mean procedure duration and fluoroscopy time were 229 ± 67 minutes and 20 ± 9 minutes, respectively, without significant differences between groups. Both the number of radiofrequency (RF) applications and RF delivery time were lower in the CMR-aided group (28 ± 18 applications vs 36 ± 18 applications, P = .037, and 19 ± 12 minutes vs 27 ± 16 minutes, P = .009, respectively). After substrate ablation, monomorphic VT inducibility was lower in the CMR-aided than in the control group (17 [32%] vs 53 [51%] patients, P = .022). After a mean follow-up period of 20 ± 19 months, patients from the CMR-aided group had a lower recurrence rate than those in the control group (10 patients [18.5%] vs 46 patients [43.8%], respectively, P = .002; log-rank P = .017). Multivariate analysis found that CMR-aided ablation (hazard ratio, 0.48 [95% Confirdence Interval (CI) 0.24-0.96], P = .037) was an independent predictor of recurrences. CMR-aided scar dechanneling is associated with a lower need for RF delivery, higher noninducibility rates after substrate ablation, and a higher VT-recurrence-free survival.

Background—: Ventricular tachycardia (VT) ablation in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) has a low success rate. A more extensive epicardial (Epi) arrhythmogenic substrate could explain the low efficacy. We report the results of combined endocardial (Endo) and Epi VT ablation and conducting channel (CC) elimination. Methods and Results—: Eleven consecutive patients with ARVD/C were included in the study. A high-density 3D Endo (321±93 sites mapped) and Epi (302±158 sites mapped) electroanatomical voltage map was obtained during sinus rhythm to define scar areas (<1.5 mV) and CCs inside the scars, between scars, or between the tricuspid annulus and a scar. The end point of the ablation procedure was the elimination of all identified CCs (scar dechanneling) and the abolition of all inducible VTs. The mean procedure and fluoroscopy time were 177±63 minutes and 20±8 minutes, respectively. Epi scar area was larger in all cases (26±18 versus 94±45 cm ² , P <0.01). The combined Endo and Epi VT ablation eliminated all clinical and induced VTs, and the addition of scar dechanneling resulted in noninducibility in all cases. Seven patients continued on sotalol. During a median follow-up of 11 months (6–24 months), only 1 (9%) patient had a VT recurrence. There was a single major bleeding event that did not preclude a successful procedure. Conclusions—: Combined Endo and Epi mapping reveals a wider Epi VT substrate in patients with ARVD/C with clinical VTs. As a first-line therapy, combined Endo and Epi VT ablation incorporating scar dechanneling achieves a very good short- and midterm success rate.

Background—: Scar heterogeneity identified with contrast-enhanced cardiac magnetic resonance (CE-CMR) has been related to its arrhythmogenic potential by using different algorithms. The purpose of the study was to identify the algorithm that best fits with the electroanatomic voltage maps (EAM) to guide ventricular tachycardia (VT) ablation. Methods and Results—: Three-dimensional scar reconstructions from preprocedural CE-CMR study at 3T were obtained and compared with EAMs of 10 ischemic patients submitted for a VT ablation. Three-dimensional scar reconstructions were created for the core (3D-CORE) and border zone (3D-BZ), applying cutoff values of 50%, 60%, and 70% of the maximum pixel signal intensity to discriminate between core and BZ. The left ventricular cavity from CE-CMR (3D-LV) was merged with the EAM, and the 3D-CORE and 3D-BZ were compared with the corresponding EAM areas defined with standard cutoff voltage values. The best match was obtained when a cutoff value of 60% of the maximum pixel signal intensity was used, both for core ( r ² =0.827; P <0.001) and BZ ( r ² =0.511; P =0.020), identifying 69% of conducting channels (CC) observed in the EAM. Matching improved when only the subendocardial half of the wall was segmented (CORE: r ² =0.808; P <0.001 and BZ: r ² =0.485; P =0.025), identifying 81% of CC. When comparing the location of each bipolar voltage intracardiac electrogram with respect to the 3D CE-CMR–derived structures, a Cohen κ coefficient of 0.70 was obtained. Conclusions—: Scar characterization by means of high resolution CE-CMR resembles that of EAM and can be integrated into the CARTO system to guide VT ablation.