Descriptive, stratigraphic, and morpho‐functional study of the myocardium and myocardial bridges in domestic pig hearts

The heart is the central organ of the cardiovascular system. The myocardium is composed of a three-dimensional network of fibers arranged in clockwise and counterclockwise helices, which are essential for proper cardiac contraction. This study aimed to describe the stratigraphic and morpho-functional pattern of the porcine myocardium to provide anatomical and physiological data applicable to both human and animal studies. The projection of myocardial bridges over the interventricular subsinuosal branch was also evaluated. Twenty hearts from domestic pigs were used. After fixation and anatomical preparation, the ventricular myocardial layers and myocardial bridges were dissected and analyzed macro and microscopically. The left ventricle was found to be composed of outer, middle, inner, and cylindrical septal layers, whereas the right ventricle consisted of outer, middle, and inner layers, with its septal wall organized as a transverse septal band. The origin of the myocardial fibers was associated with the four fibrous rings of the cardiac skeleton, and their insertion occurred predominantly within the walls of the interventricular septum. Myocardial bridges were classified as dorsal, middle, or ventral and were present in 65% of the hearts analyzed. Histological and ultrastructural analyses demonstrated collagen and elastic fibers between the myocardial bridges and the associated vessels. It is concluded that the layered and structural organization of the porcine myocardium are consistent with the distinct hemodynamic demands of each ventricle. These findings reinforce the functional significance of myocardial architecture in ventricular mechanisms and support the use of the pig as a relevant model for comparative and translational cardiovascular research. The topographic analysis of myocardial bridges revealed their depth-related relationship with the vascular wall and with the outer and middle myocardial layers, suggesting a potential influence on coronary blood flow and cardiac vascularization.