Regional Stress and Strain in Healthy and Diseased Ventricular Myocardium
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The primary function of the heart is fundamentally mechanical. The basic measures of myocardial mechanics are the three-dimensional stresses and strains, which depend on position and orientation in the myocardium, and vary in time through the cardiac cycle. A host of physiological and pathophysiological processes are directly or indirectly regulated by regional myocardial stress and strain. Most of these factors — such as coronary flow and myocyte energetics, excitation and arrhythmia, hypertrophy and development, remodeling and repair — themselves affect stress and strain in the ventricular wall. For example, increased wall stress due to altered hemodynamic load can cause ventricular hypertrophy, which in turn alters wall stress by changing chamber geometry and material properties. If this feedback loop establishes a new equilibrium, hypertrophy can be compensated. But if stress continues to increase, a transition to decompensated hypertrophy and pump failure can ensue. As treatments for myocardial infarction and ischemia have improved, the incidence of congestive heart failure has risen alarmingly. Some important load-induced responses are now known to be regulated by stress and strain directly at the level of the myocyte, endothelial cell and fibroblast. For these advances in basic cardiac biology to be applied in the clinical setting, a better understanding of the biomechanics of ventricular remodeling in-vivo will surely be needed.
KeywordsDiffusion Tensor Imaging Ventricular Wall Wall Stress Regional Stress Magnetic Resonance Elastography
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