Timely diagnosis of disorders of the pumping function of the heart and its inotropic state, strained compensation, and failure of the compensatory potential are important for selecting the treatment strategy and predicting the disease course in critical patients. This paper presents the results of many-year investigations in this field. The contribution of right-ventricular insufficiency to the development of circulatory disorders is validated, as is the effect of artificial ventilation of the lungs on the function of the myocardium. Relationship between the severity of hemodynamic disorders and pathological process is described. The author validates the use of test exposures and functional tests in intensive care departments in order to assess the functional insufficiency and reduction of the reserve potential of the right and left heart. The potentialities of spectral analysis of the electrocardiographic signal in the early diagnosis of myocardial dysfunction and prediction of the disease course is shown.