Introduction: Optimizing Cardiac Resynchronization Therapy (CRT) is hindered by ECG limitations and standard criteria in assessing ventricular synchronization during the procedure. Imageless Electrocardiographic Imaging (ECGI) offers a rapid, non-invasive method to assess ventricular synchronization by mapping local activation times (LAT) without requiring cardiac imaging. Purpose: This study aims to identify ECGI-derived metrics for determining effective ventricular resynchronization in left bundle branch block (LBBB) patients undergoing CRT. Methods: We evaluated an imageless ECGI system to quantify ventricular synchronization using Total Activation Time (TAT) and Ventricular Electrical Uncoupling (VEU) during CRT in 36 LBBB patients, compared to baseline LBBB state and 28 healthy controls. Results: CRT significantly reduced mean TAT (119±16 vs 77±15 ms, p<0.001) and VEU (45±10 vs 8±9 ms, p<0.001). Final CRT VEU was comparable to healthy controls (7±6 ms, p=NS), indicating restored interventricular synchrony. Conclusion: Imageless ECGI provides feasible, non-invasive TAT/VEU metrics, tracking CRT effects effectively and offering the potential for standardized, real-time guidance beyond subjective ECG interpretation.