Myocardial length-tension sarcomere relationships

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Abstract
Sarcomere length-developed tension curves were determined for isolated rat left ventricular papillary muscle. Maximum isometric tension was developed at sarcomere lengths of 2.07+0.03 [mu] with the experimental methods employed. With this value as a reference, intraventricular pressure-ventricular sarcomere length curves were derived for rat ventricles in situ in open-chest animals. Sarcomere length increased from 87 to 96% of optimum length as pressure increased from 0 to 24 cm H2O but showed little further increase at high pressures and did not exceed optimum length at a pressure of 96 cm H2O. The functional position of ventricular sarcomeres on the length-tension curve was studied in potassium-arrested ventricles following a variety of manipulations. The data indicate a maximum range of diastolic sarcomere lengths of 92-95% of optimum, in animals with an intact thorax. Myocardial sarcomeres may function normally at diastolic lengths within 10% of optimum for tension production. It may be difficult or impossible to exceed optimum length under in situ conditions.

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