Trivariate correlation analysis of hemodynamic indices of the cardiovascular system in rabbits with diphtheria showed that adaptation of this system to direct action of diphtherin can be visualized by analysis of trivariate correlation tightness for indices of intraventricular pressure in the left and right ventricles and indices of systemic blood pressure. Using empirical production functions for systemic blood pressure indices we found that the contribution of intraventricular pressure in the left and right ventricles on blood pressure values is changed in diphtheria compared to the control. Basing on entropy analysis we established that the regimen of control over values of working intraventricular pressure in both left and right ventricles in diphtheria is changed from quasidetermined to stochastic.