[An analysis of the shifts in the heart pump function during pressure changes in the initial portion of the aorta]

External occlusion at the beginning of aorta induced different shifts of the cardiac output systemic fraction in different degrees of the AP raise. Various mechanisms of the changes in the left ventricle output were found to depend upon the degree of the AP raise in the aorta. An increase of systemic fraction in 1 to 60 mm Hg raise of the AP was due to changes in contractile activity of the myocardium, whereas in 61 to 90 mm Hg raise it was due to an increase in terminal diastolic pressure. If the AP increment exceeded 100 mm Hg a decrease of the systemic fraction occurred.