Since the pattern of electrical activation in the myocardium, which underlies cardiac pump function, is dependent on fiber orientation, ventricular activation maps were generated and used to analyze the correspondence between the simulation results with LDRB and DTI-derived fiber orientations. Two sets of simulations were performed. The first set was performed by pacing the canine ventricles with LDRB and DTI-derived fiber orientations at the LV epicardium midway between the apex and base to elicit transmural electrical wave propagation, and the second set was performed by pacing at the LV endocardial apex to elicit apicobasal propagation. At each location, the myocardium was paced at a cycle length of 600 ms for 10 beats with stimuli of 2 ms duration and twice diastolic threshold amplitude. Activation maps were generated for the 10th beat by computing, at each location within the myocardium, the moment in time when the action potential upstroke velocity reached maximum. Differences in the activation maps between simulations with LDRB and DTI-derived fiber orientation were quantified using the methods of Han et al.,13 (link) in which a relative difference (RD), root mean square difference (RMSD), and correlation coefficient (CC) were computed for each pacing protocol.