心衰时产生的一系列血流动力学改变,使心脏前、后负荷增加,影响心功能的恢复。血管扩张药可降低心脏前或后负荷,提高心排量,减轻心衰症状。有的血管扩张药主要减低前负荷(小静脉扩张药),有的主要减低后负荷(小动脉扩张药),有的兼有扩张小静脉、小动脉的作用。使用小动脉扩张药后,小动脉阻力血管扩张,外周阻力下降,后负荷降低,心排量可随之增加,而且由于后负荷下降,心肌耗氧减少,心肌收 Heart failure when a series of hemodynamic changes, the heart before and after the load increases, affecting the recovery of cardiac function. Vasodilators can reduce pre-or post-cardiac load, improve cardiac output and reduce heart failure symptoms. Some vasodilators mainly reduce the preload (small venous dilatation drug), and some mainly reduce the afterload (arteriolar dilation), and some dilate the role of small veins, small arteries. Arterioles after dilation of drug resistance, arteriolar vasodilation, decreased peripheral resistance, decreased afterload, cardiac output may be increased, but also due to post-load decreased myocardial oxygen consumption decreased myocardial income