Getting to the heart of cardiac remodeling; how collagen subtypes may contribute to phenotype

► Collagen I and III molecules organize in a subtype-specific manner at fiber level. ► Important biomechanical differences in these fiber subtypes exist. ► A relatively higher Young's elastic modulus is found in collagen I fibers. ► Collagen III fibers undergo plastic deformation sooner and are less energy efficient. ► Both fiber subtypes show augmented stiffness associated with atrial fibrillation.