在前负荷增加时,使心肌收缩力加强,心搏出量随之增加,当心室舒张末期压超过20毫米汞柱时,不但不能提高心肌收缩力,反使心搏出量降低,并能导致肺微血管压增高,使肺部充血。后负荷增加时,心搏出量降低,使皮肤及心、脑、肾等重要器官灌注量不足。前负荷与后负荷的发生既彼此关连又 In the preload increases, so that myocardial contractility strengthened, cardiac output will increase, when the ventricular end-diastolic pressure exceeds 20 mm Hg, not only can not improve myocardial contractility, to reduce cardiac output, and can lead to Pulmonary microvascular pressure increased, so that lung congestion. After the load increases, the cardiac output reduced, so that the skin and heart, brain, kidney and other vital organs perfusion is insufficient. The occurrence of preload and postload are related to each other