In the realm of artificial intelligence, the generation of realistic training data for supervised learning tasks presents a significant challenge. This is particularly true in the synthesis of electrocardiograms (ECGs), where the objective is to develop a synthetic 12-lead ECG model. The primary complexity of this task stems from accurately modeling the intricate biological and physiological interactions among different ECG leads. Although mathematical process simulators have shed light on these dynamics, effectively incorporating this understanding into generative models is not straightforward. In this work, we introduce an innovative method that employs ordinary differential equations (ODEs) to enhance the fidelity of generating 12-lead ECG data. This approach integrates a system of ODEs that represent cardiac dynamics directly into the generative model's optimization process, allowing for the production of biologically plausible ECG training data that authentically reflects real-world variability and inter-lead dependencies. We conducted an empirical analysis of thousands of ECGs and found that incorporating cardiac simulation insights into the data generation process significantly improves the accuracy of heart abnormality classifiers trained on this synthetic 12-lead ECG data.