Characterization of the Porcine Cardiac Conduction System and Electrocardiogram: Implications for Using the Pig in...

The domesticated pig (Sus scrofa domesticus) is widely used as a large animal model in cardiovascular research due to its anatomical and physiological similarities of its heart to the human heart, particularly concerning coronary circulation. However, notable differences in action potential shape, electrical activation pattern, as well as ion channel composition between porcine and human hearts limit translatability.

This study investigates the relationship between the distribution of the cardiac Purkinje fiber network in the pig and the heart's mean electrical axis. We hypothesize that an intramural Purkinje fiber network results in ventricular electrical activation in an apex-to-base direction. The morphology and distribution of the porcine conduction system were assessed histologically, while electrical activation was evaluated using ECG recordings in both the Einthoven and orthogonal lead configurations. The Purkinje fiber network was found in the subendocardium and extended deep into the ventricular walls. The mean electrical axis exhibited a cranial orientation consistent with apex-to-base ventricular activation.

These results suggest that in the pig, the mean electrical axis is influenced more by the presence of an intramural Purkinje fiber network rather than by left ventricular mass as seen in humans. This study underscores important species-specific differences in ventricular electrical activation and highlights the need for caution when extrapolating electrophysiological findings from porcine models to humans.