Intramural mapping of intramural septal ventricular arrhythmias.

BACKGROUND: Intramural ventricular arrhythmias (VAs) can originate in patients with or without structural heart disease. Electrogram (EGM) recordings from intramural sources of VA have not been described thoroughly. OBJECTIVE: We hypothesized that the presence of scar may be linked to the site of origin (SOO) of focal, intramural VAs. METHODS: In a series of 21 patients (age: 55 ± 11 years, 12 women, mean ejection fraction 43 ± 14%) in whom the SOO of intramural VAs was identified, we analyzed bipolar EGM characteristics at the SOO and compared the findings with the endocardial breakout site. The patients were from a pool of 86 patients with intramural VAs referred for ablation. RESULTS: In 16/21 patients intramural scarring was detected by cardiac magnetic resonance (CMR) imaging In patients in whom the intramural SOO was reached, intramural bipolar EGMs showed a lower voltage and had broader EGMs compared to the endocardial breakout sites (0.97 ± 0.56 vs. 2.28 ± 0.15 mV, p = .001; and 122.3 ± 31.6 vs. 96.5 ± 26.3 ms, p < .01). All intramural sampled sites at the SOO had either low voltage or broad abnormal EGMs. The activation time was significantly earlier at the intramural SOO than at breakout sites (-36.2 ± 11.8 vs. -23.2 ± 9.1 ms, p < .0001). CONCLUSIONS: Sites of origin of intramural VAs with scar by CMR display EGM characteristics of scarring, supporting that scar tissue localizes to the SOO of intramural outflow tract arrhythmias in some patients. Scarring identified by CMR may be helpful in planning ablation procedures in patients with suspected intramural VAs.

Role of endocardial ablation in eliminating an epicardial arrhythmogenic substrate in patients with Brugada syndrome.

BACKGROUND: Epicardial ablation is occasionally limited by coronary artery (CA) injuries or epicardial fat (EF). OBJECTIVE: The purpose of this study was to evaluate the anatomic obstacles that prevent ablation of epicardial abnormal potentials (EAPs) in patients with Brugada syndrome (BrS) and to investigate the feasibility of EAP elimination by endocardial right ventricular (RV) ablation. METHODS: This study included 16 BrS patients with previous ventricular fibrillation (VF), including 10 with an electrical storm. Data from multidetector computed tomography were assessed, and the proximity of the CA and EF was correlated with EAPs. RESULTS: EAPs were present in the epicardial RV outflow tract and RV inferior wall in all patients and 12 patients (75%), respectively. These EAPs were present within 5 mm of the main body and branches of the right CA in 14 patients (87.5%). However, only 1.4% ± 2.9% of the EAP area was covered with thick EF (≥8 mm). Partial EAP elimination by endocardial RV ablation was feasible in all 10 patients, with 53.3% successful endocardial RV radiofrequency applications for eliminating EAPs. After the procedure, VF remained inducible in 37.5% of the patients. During the 25.1 ± 29.1 months of follow-up, no patients experienced an electrical storm, and VF burden significantly decreased (median VF episodes before and after ablation: 7 and 0, respectively). CONCLUSION: EAPs are near the CA in most BrS patients, thereby requiring caution during epicardial ablation, whereas EF is less of an issue. Endocardial ablation is feasible to eliminate some EAPs and may be combined with epicardial ablation.

Impact of Intramural Scar on Mapping and Ablation of Premature Ventricular Complexes.

OBJECTIVES: This study sought to determine intramural scar characteristics associated with successful premature ventricular complex (PVC) ablations. BACKGROUND: Ablating ventricular arrhythmias (VAs) originating from intramural scarring can be challenging. Imaging of intramural scar location may help to determine whether the scar is within reach of the ablation catheter. METHODS: Mapping and ablation of premature ventricular complexes (PVCs) was performed in a consecutive series of patients with intramural scarring and frequent PVCs. Data from delayed enhanced cardiac magnetic resonance were assessed and the proximity of the endocardium containing the breakout site to the intramural scar was correlated with outcomes. RESULTS: Fifty-six patients were included, and intramural VAs were successfully targeted in 42 patients (75%) and ablation failed in 14 patients (25%). Scarring was more superficial to the endocardium in patients with successful ablations compared with patients with failed procedures (0.35 mm [interquartile range (IQR): 0.22 to 1.20 mm] vs. 2.45 mm [IQR: 1.60 to 3.13 mm]; p < 0.001). In 18 (32%) patients, ablation at the breakout site resulted in a significant change of the PVC-QRS morphology that could successfully be ablated in 9 of 12 patients from another anatomical aspect of the wall harboring the intramural scar. The scar was larger in size (1.79 cm3 [IQR: 1.25 to 2.85 cm3] vs. 1.00 cm3 [IQR: 0.59 to 1.68 cm3]; p < 0.005) compared with patients who did not have a change in the PVC-QRS morphology with ablation. CONCLUSIONS: VAs in patients with intramural scaring can be successfully ablated especially if the intramural scar is within close proximity to the anatomic area containing the breakout site. Changes in the QRS-PVC morphology often precede successful ablation at another breakout site and indicate larger intramural scars.

Risk stratification in patients with nonischemic cardiomyopathy and ventricular arrhythmias based on quantification of intramural delayed enhancement on cardiac magnetic resonance imaging.

INTRODUCTION: Intramural scarring is a risk factor for sudden cardiac death. The objective of this study was to determine the value of scar quantification for risk stratification in patients with nonischemic cardiomyopathy (NICM) undergoing ablation procedures for ventricular arrhythmias (VA). METHODS AND RESULTS: Cardiac late gadolinium-enhanced magnetic resonance imaging was performed in patients with NICM referred for ablation of premature ventricular complexes or ventricular tachycardia (VT). Only patients with intramural delayed enhancement were included. Scar volume was measured and correlated with immediate and long-term outcomes. Receiver operator curves, Wilcoxon signed-rank testing, and logistic regression were used to compare patient characteristics. The study consisted of 99 patients (74 males, mean age: 59.6 [54.0-68.1] years, ejection fraction [EF]: 46.0 [35.0-60.0]%). Patients without clinical VT or inducible VT had smaller total and core scar size compared to patients with a history of VT or inducible VT (total scar 1.12 [0.74-1.79] cm3 vs 7.45 [4.16-12.21] cm3 , P < .001). A total scar volume of greater than or equal to 2.78 cm3 was associated with inducibility of VT (AUC 0.94, 95% CI [0.89-0.98], sensitivity 85%, specificity 90%). Scar volume was associated with VT inducibility independent of a prior history of VT or the preprocedure EF (adjusted OR 1.67 [1.24-2.24]/cm3 , P < .01). CONCLUSION: Quantification of scar size in patients with intramural scarring is useful for risk stratification in patients with NICM and VA independent of the EF or a prior history of VT. Scar characteristics of patients without a history of VT who have inducible VT are similar to patients with a history of VT.

Stepwise Approach for Ventricular Tachycardia Ablation in Patients With Predominantly Intramural Scar.

OBJECTIVES: The goal of this study was to assess the value of a stepwise, image-guided ablation approach in patients with cardiomyopathy and predominantly intramural scar. BACKGROUND: Few reports have focused on catheter-based ventricular tachycardia (VT) ablation strategies in patients with predominantly intramural scar. METHODS: The study included patients with predominantly intramural scar undergoing VT ablation. A stepwise strategy was performed consisting of a localized ablation guided by conventional mapping criteria followed by a more extensive ablation if VT remained inducible. The extensive ablation was guided by the location and extent of intramural scarring on delayed enhanced-cardiac magnetic resonance imaging. A historical cohort who did not undergo additional extensive ablation was identified for comparison. A novel measurement, the scar depth index (SDI), indicating the percent area of the scar at a given depth, was correlated with outcomes. RESULTS: Forty-two patients who underwent stepwise ablation (median age 61 years [interquartile range: 55 to 69 years], 35 male patients, median left ventricular ejection fraction 36.0% [25.0% to 55.0%], ischemic [n = 4] or nonischemic cardiomyopathy [n = 38]) were followed up for a median of 17 months (8 to 36 months). A stepwise approach resulted in a 1-year freedom from VT, death, or cardiac transplantation of 76% (32 of 42). Patients who underwent additional extensive ablation had a lower risk of events than a clinically similar historical cohort (N = 19) (hazard ratio: 0.30; 95% CI: 0.13 to 0.68; p < 0.004). SDI>5mm was associated with worse long-term outcomes (hazard ratio: 1.03; 95% CI: 1.01 to 1.06%; p = 0.03), SDI>5mm >16.5% was associated with failed ablation (area under the curve: 0.84; 95% CI: 0.71 to 0.97). CONCLUSIONS: Stepwise ablation using delayed enhanced-cardiac magnetic resonance guidance is a novel approach to VT ablation in patients with predominantly intramural scarring. The SDI correlates with immediate procedural and long-term outcomes.