[Influence of mechanical conditions on myocardial chronoinotropy]

The force-frequency relationships in isometric, isotonic and auxotonic regimes of contractions have been analysed in right rabbit papillary muscles. The uncorrelated Hauss input sequence of interstimulus intervals was used. For studied mechanical regimes a number of differences have been shown. These differences were in: 1) coefficients of contraction amplitude variation (with the same input stimulus dispersion); 2) dependence of mechanical activity upon the amplitude of previous contraction; 3) force-frequency relationships calculated with regression equations. The nature of revealed differences and usage of chronotropic indexes as a measure of contractility have been discussed.