ANALYSIS OF SOME MECHANICAL-PROPERTIES OF QUIESCENT MYOCARDIUM

The mechanical behaviour of quiescent rat papillary muscle has been studied by using two different experimental tests. In the first (Displacement Controlled test), predetermined length changes were imposed to the muscle and the corresponding tensions were recorded. In the second (Force Controlled test), a predetermined load was applied to and removed from the specimen and the corresponding length changes were recorded. By means of this procedure different stress-strain relationships, stress relaxation and its reversal, creep and its recovery, were obtained. The tests were conducted in order to study (1) the effects of deformation magnitude, (2) the asymmetries and the hysteretic behaviour and (3) the influence of viscous phenomena (elastic after-effects) duration. Strain rate sensitivity of papillary muscle has not been investigated. Experimental findings are discussed accounting for the possibility of a quantitative separation of elasticity, viscosity and plasticity in quiescent myocardium. The results obtained are examined in view of their application to rheological cardiac muscle models. © 1979.