Radial Variation in Residual Stress in Mouse Lv Is Likely to Be Highly Nonlinear

INTRODUCTION Residual stress in organs has implications not only for stress gradients in the tissue, but also for growth and remodeling [1-3]. In the heart, it has been proposed that residual stresses are one mechanism by which the normal left ventricle maintains optimal function in terms of fiber stress [4,5]. Residual stress can also play a role in remodeling during disease. For example, altered residual stress in the heart may be a beneficial adaptation to the mechanical alterations seen in the osteogenesis imperfecta murine model of type I collagen deficiency [6], and it could play a role in ventricular geometric remodeling [7,8]. Residual strain inherently does not satisfy compatibility, and it is thought that a biological material can only be truly "stress-free" if a large number of cuts are made to relieve all of the residual stress which may exist at the microscopic level. Yet, in the heart and arteries, it is generally assumed that a single radial cut across an axial section of tissue relieves all of the residual stress, and most theoretical and computational analyses have made this assumption [9,10]. Although the material near the cut edge will have no residual circumferential stress, we show that significant residual stress still exists in much of the ring after a radial cut is made in the mouse myocardium used in the present study. Indeed, further stress is relieved by making a circumferential cut after the radial cut. A modeling analysis shows that these secondary cut reveals significantly different, and possibly much more complex, distributions of residual stress and strain than those predicted from models with a single radial cut.