Computed Tomography–Derived Abrupt Wall-Thickness Transitions as Complementary Markers of Ventricular Tachycardia Substrate in Ischemic Cardiomyopathy

BACKGROUND Functional substrate mapping for ventricular tachycardia (VT) is activation dependent and may incompletely delineate critical substrate. OBJECTIVES This study sought to determine whether abrupt wall-thickness transitions on computed tomography angiography (CTA)-derived maps colocalize with mappable VT isthmus boundaries in patients with ischemic cardiomyopathy (ICM). Associations with deceleration zones (DZs) and VT-related sites in unmappable VTs were also assessed. METHODS Color-coded left ventricular wall-thickness maps were generated from preprocedural CTA in 21 patients with ICM (median age: 67.0 years) using commercially available software. Abrupt wall-thickness transitions were defined as ≥3 millimeter change within a local 1-cm region based on closely spaced color transitions. Their spatial relationships with DZs during baseline rhythm mapping, mappable VT isthmus boundaries, and pace map-defined exit sites in unmappable VTs were evaluated. RESULTS Among 32 substrate maps, 25 DZs were identified, with 92% colocalizing with abrupt wall-thickness transitions. Of 40 VTs, activation mapping was feasible in 20. In these mappable VTs, VT isthmus boundaries colocalized with DZs in 10 (50.0%) and with abrupt wall-thickness transitions in 14 (70.0%). Among the unmappable VTs, good pace maps consistent with VT exit sites were identified in areas of abrupt wall-thickness transition in 17 of 20 VTs (85.0%). On segment-level analysis, the positive predictive value of abrupt wall-thickness transitions for identifying DZs and VT isthmus boundaries was modest (28.3% and 18.9%, respectively). CONCLUSIONS Abrupt wall-thickness transitions on CTA-derived maps frequently colocalized with mappable VT isthmus boundaries and DZs in patients with ICM, supporting their role as complementary markers.