[Analysis of systemic hemodynamics in altered hydraulic resistance of the initial portion of the aorta]

The changes of cardio- and hemodynamics on increase of hydraulic resistance in the initial part of aorta under conditions of external occlusion (EO) of the ascending aorta or internal occlusion (IO) of aortic valve opening or of the ascending aorta lumen, were studied in anesthetized cats. Under EO to 50% of square section of the ascending aorta a considerable increase of cardiac output (CO) with small rise of aortic pressure proximal to site of occlusion (AP-1) was observed. Further EO was accompanied by a decrease of CO with a more pronounced rise of AP-1. AP distal to EO kept unchanged within wide range of aorta narrowing. 10 of ascending aorta lumen caused similar correlations of CO, left ventricle systolic pressure (LVP) and AP distal to the occlusion site. Under 10 of aortic valve opening, progressive decrease of CO with simultaneous increase of LVP and lowering of AP takes place. The role of the coronary blood flow as a factor increasing the myocardial contractility under increase of AP and the significance of baroreceptor reflexes, are discussed.