An inverse-forward approach was assessed to compute a 12-lead ECG from body surface potential mapping data. Using simulated data (n=21), reconstructed 12-lead ECGs had accurate morphology (CC>0.88), amplitude (RMSE<8.6%) and mean electrical axis during both depolarization and repolarization ( ∆� < 17 degrees). There was no significant deterioration in results until body surface mapping electrodes were removed within 6 cm of any 12-lead electrode (p < 0.0001). Reconstructed 12-lead ECGs of 6 CRT candidates captured the measured mean electrical axis during the QRS and Twave ( ∆� = 6.2 ± 4.7 and 14.2 ± 2.6 degrees respectively). Furthermore, additional clinically relevant features were reproduced allowing the correct identification of left bundle branch block and nonspecific intraventricular conduction disturbance, including: broad/notched R-waves, presence/absence of Q-wave, and direction of T-waves.