Quantification of Coupled Stiffness and Fiber Orientation Remodeling in Hypertensive Rat Right-Ventricular Myocardium Using 3D Ultrasound Speckle Tracking with Biaxial Testing

This study quantified how chronic pulmonary hypertension alters the mechanical behavior and transmural fiber architecture of right ventricular myocardium in a rat model. Using biaxial mechanical testing combined with three-dimensional ultrasound speckle tracking, the authors demonstrated significant stiffening, increased anisotropy, and loss of the normal helical fiber architecture across myocardial thickness in pressure-overloaded tissue. Hypertensive myocardium exhibited reduced transmural variation in fiber orientation and altered stress–strain responses compared to normotensive controls. These findings provide mechanistic insight into right ventricular remodeling and dysfunction associated with pulmonary hypertension.