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周围血管扩张药物减少心室后负荷对于充血性心力衰竭的临床应用,是治疗学上一个新的发展,在收缩期中(心室后负荷)应用全身的血管扩张剂有两种机理可以减少左室壁张力:第一,这些药物可以减少全身的血管阻力,因此在左室喷射时减少了主动脉阻抗,左室就能输出较大的心搏量与心排量,上升的周围血管阻力降低后,降低的心排量通常亦上升到相同程度,动脉血压没有或仅有轻度下降,伴有很轻微的心率增快。第二,周围血管扩张药物也可以松弛全身静脉血管床的平滑肌,因而使周围静脉血储留,回心血量减少,其结果是左室充盈压与舒张末期容量(前负荷)皆减少,因而肺充血缓解;除此以外,由于周围血管扩张剂引起的心室容量与主动脉阻抗减少,在心脏收缩时左室壁张力减少而使心肌需氧量降低。因此,治疗急性与慢性充血性心力衰竭的主要目的,可以用全身血管扩张剂疗法降低左室后负荷而完成:(1)使低心排量增加;(2)降低心室充盈压使肺充血缓解;(3)减少心肌需氧量使心室缺血好转;(4)对于心率与血压没有或者仅有轻微变化。现代临床上应用的主要血管扩张药物(硝普钠、苄胺唑啉,三硝酸甘油酯与阿方那特)对于周围动脉与静脉血管床有不同的作用,硝普钠与阿方那特对于全身动脉与静脉平滑肌产生接近相等的松弛作用,故增加心排量减少 LVEDP 与 MVO_2;苄胺唑啉对于动脉血管床比静脉血管床有较大的效应,因此相对的使心排量增加较大于降低 LVEDP;与此对比,舌下含服硝酸盐主要作用于全身的静脉系统,因此降低 LVEDP 与 MVO_2,但是在大多数病人中心排量下降或不变。
Vascular Dilatation Drugs to Reduce Post Ventricular Postload Clinical application of congestive heart failure is a new development in therapeutics. There are two mechanisms by which systemic vasodilators can be applied during systole (post-ventricular) to reduce left ventricular wall tension : First, these drugs can reduce systemic vascular resistance, thus reducing the aortic impedance when left ventricular injection, the left ventricle will be able to output greater stroke volume and cardiac output, decreased peripheral vascular resistance decreased, decreased Often the cardiac output also rises to the same extent, with no or only mild decrease in arterial pressure, with a slight increase in heart rate. Second, the peripheral vasodilators can also relax the smooth muscle of the venous bed of the whole body. As a result, the peripheral venous blood is stored and returned to the lesser. As a result, left ventricular filling pressure and end-diastolic volume (preload) are reduced, Hyperemia; In addition, due to peripheral vasodilator-induced ventricular volume and aortic impedance decreased in the contraction of the left ventricular wall tension decreased myocardial oxygen demand decreased. Thus, the primary goal of treating acute and chronic congestive heart failure can be accomplished by systemic vasodilator therapy to reduce left ventricular afterload: (1) increased low cardiac output; (2) decreased ventricular filling pressure to relieve pulmonary congestion ; (3) reduce myocardial oxygen demand so that ventricular ischemia improved; (4) no or only slight changes in heart rate and blood pressure. Modern clinical application of the main vasodilators (sodium nitroprusside, benzylazoline, glyceryl trinitrate and alfalfa) for the peripheral arteries and venous vascular bed have a different role, sodium nitroprusside and alfalfa for Systemic arteries and venous smooth muscle produce nearly equal relaxation, so increase cardiac output to reduce LVEDP and MVO_2; Benzamid for arterial vascular bed than the venous bed has a greater effect, so the relative increase in cardiac output more than In contrast, sublingual nitrates mainly act on the systemic venous system, thus reducing LVEDP and MVO_2, but in the majority of patients, cardiac output drops or does not change.