Non-invasive electrocardiographic imaging (ECGI) for reentrant ventricu-lar tachycardia (VT) suffers from spatial incoherence due to circular activa-tion, hindering isthmus localization. We introduce a Complex Gaussian Pro-cess (CGP) framework to model local activation time (LAT) circular topolo-gy, improving spatial consistency. We compute conduction velocity (CV) and curl from high-resolution CGP-LAT maps, hypothesizing the isthmus exhibits slow conduction (high gradient) and low curl. The method was eval-uated on simulated (N=4, ground truth) and patient (N=1, clinical electroana-tomical mapping) VT data against standard deflection-based LAT maps. CGP-LAT maps showed significantly improved spatial coherence. In simula-tions, CGP yielded superior propagation direction accuracy (mean cosine 0.81 vs 0.64) and lower vector field error (RMSE 0.91 vs 1.08 ms/mm). Ap-plying CV/curl criteria to CGP maps allowed more precise simulated isthmus localization. In patients, CGP analysis revealed clearer CV/curl patterns, identifying channels concordant with clinical annotations and EAM. Addressing reentry's topology, CGP combined with wavefront analysis of-fers a promising non-invasive tool for improved VT isthmus localization.