The dynamic twisting of the left ventricle: a computer study.

A mathematical analysis which relates the dynamic twisting motion of the heart around its longitudinal axis to the mechanical function of the left ventricle (LV) is presented. The study thus extends our earlier model which relates the micro-scale sarcomere dynamics, the fibrous structure of the myocardium, and the electrical transmural activation wave to the global LV function. The analysis demonstrates that although the angular twisting motion of the heart moderates the sarcomere length (SL) and the strain rate distributions throughout the myocardium, the global characteristics of the LV function are almost independent of the twisting phenomenon. The endocardial sarcomeres are nevertheless subjected to higher strains and higher (negative) strain rates than the corresponding (positive) epicardial sarcomeres. Utilizing the sarcomere stress length area to predict oxygen demand, it is shown that the twisting motion of the heart produces the metabolic gradient across the LV wall. In spite of the moderating effect of the twist, a larger than normal gradient in oxygen demand is predicted for cases of concentric hypertrophy.