Significance of Coherent Mapping in unveiling slow conduction zones of ventricular tachycardia substrate in ischemic cardiomyopathy

Abstract

Abstract Introduction Ventricular tachycardia (VT) presents a formidable challenge, particularly in cases with extensive myocardial scar tissue, complicating critical ablation site identification. Prolonged interventions not only extend procedural durations but also heighten the risk of complications. This study aimed to assess the efficacy of coherent mapping techniques in precisely locating regions of slow conduction within scar tissue and explored potential correlations with electrophysiological markers in scar-related VT. Methods Seventeen patients (mean age: 61.6 ± 9.2 years, mean EF: 28 ± 9%) with ischemic cardiomyopathy (ICM) and frequent implantable cardioverter-defibrillator (ICD) shocks underwent high-density (>2000 points) left ventricular (LV) substrate mapping (15 endo, 2 epicardial) during sinus or right ventricular (RV) pacing and ablation. Coherent mapping tool was utilized for the identification of slow conduction, demonstrated by vector thickening. Bipolar low voltage areas (LVAs) below 0.5 mV were defined as dense scar, and bipolar voltage between 0.5 and 1.5 mV was defined as the border zone (Figure, panel A). Late potentials (LPs) and local abnormal ventricular activities (LAVA) were manually identified and tagged. Isochronal late activation mapping (ILAM) was also performed to elucidate the functional properties of the substrate (Figure, Panel B). Results LPs and LAVA were identified in all cases, with a mean number of LPs being 10.0 ± 7.1. Of these, 14/17 cases had LPs located in dense scar, while 4/17 cases had LPs in the border zone. The mean area of LAVA was 9.9 ± 7.7 mm², located in dense scar in 6/17 cases and in the border zone in 15/17 cases. Average deceleration zones (DZ, >3 isochrones in 1 cm radius) identified by ILAM was 2 ± 1. Coherent mapping consistently identified slow conduction zones adjacent to LVA in all cases, with these coherent map-based slow conduction zones (CM-SCZ) located in dense scar in 3/17 cases and in the border zone in 14/17 cases. The distance of CM-SCZ to LPs was 12.6 ± 13.9 mm (in 4 cases, LPs were recorded on the spot), and the distance to LAVAs was 18.8 ± 13.7 mm (in 2 cases, LAVAs were recorded on the spot). CM-SCZ was colocalized with DZ in 14/17 of the patients. Ablation lesions covered CM-SCZ in 10/17 cases. Over a mean follow-up duration of 11 ± 6.5 months, 4 patients experienced VT recurrence, with 3 having no ablation lesions covering CM-SCZ, and 2 patients died due to pump failure. Conclusion This study underscores the significance of coherent mapping in refining the understanding of VT substrate in ICM. Identifying and ablating CM-SCZ during substrate-based mapping may provide a potential additional benefit for VT ablation. Nevertheless, larger studies are needed to clarify the prognostic significance and validate the clinical benefits of this approach.Figure 1