Does the twisting motion of the left ventricle moderate nonuniformities in sarcomere shortening across the myocardial wall?
The twisting motion of the heart is a fundamental biomechanical mechanism that maintains sarcomere function within its physiological range by moderating transmural nonuniformities in shortening.
The contraction of the left ventricle (LV) is manifested by a distribution of strains and strain rates throughout the muscle thickness. Using a nested shell spheroidal model of the LV, which accounts for a fiber angle distribution from + 60°at the endocardium to -60° at the epicardium, and the radial electrical activation pattern from the endocardium to the epicardium, it can be shown that endocardial layers undergo higher strains than the epicardial layers throughout the cardiac cycle, and higher length changes characterize the endocardial sarcomeres relative to the epicardial sarcomeres. However, the calculated nonuniformities in the sarcomeres' shortening are significantly moderated when the physiological twisting motion of the LV around the longitudinal axis is accounted for. Thus, the twisting motion of the heart is a basic mechanism by which the sarcomere function is maintained within its physiological range.
Beyar et al. (Tue,) studied this question.
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