Losano G, Gattullo D, Pagliaro P
Dipartimento di Anatomia e Fisiologia Umana Università di Torino, Italy.
Cardioscience. 1995 Mar;6(1):13-7.
The mean coronary blood flow increases in response to an increase in myocardial oxygen consumption. Conversely, an increase in coronary perfusion is itself reported to induce an increase in myocardial oxygen consumption. Such an effect can be explained by stretching of the myocardial fibers surrounding the vessels, which become more distended with an increase in perfusion. The flow in the left descending and circumflex coronary arteries is reduced in systole because of the compression exerted by the contracting myocardium on the intramyocardial vessels. Due to the thinner wall of the right ventricle, this reduction is not obvious in the right coronary artery. The intramyocardial pump model provides a satisfactory explanation of the mechanism by which contraction reduces the flow. It also explains the attenuation of the diastolic-systolic oscillations of flow which occurs in the presence of a stenosis of a large epicardial artery. The varying elastance model shows the dependence of the extent of the reduction of the flow in systole on myocardial contractile force rather than on the pressure developed in the ventricle by the contraction. However, although the ventricular systolic pressure does not affect the flow in hearts with a relatively thick wall, it contributes to the systolic reduction of flow in hearts with a relatively thin wall. Owing to a mechanism involving the coronary capacitance, contraction is also responsible for the level of coronary flow in diastole.
冠状动脉平均血流量会随着心肌耗氧量的增加而增加。相反，据报道冠状动脉灌注增加本身会导致心肌耗氧量增加。这种效应可以通过血管周围心肌纤维的拉伸来解释，随着灌注增加，这些纤维会更加扩张。由于收缩的心肌对心肌内血管施加的压迫，左冠状动脉前降支和左旋支的血流在收缩期会减少。由于右心室壁较薄，这种减少在右冠状动脉中并不明显。心肌内泵模型对收缩导致血流减少的机制提供了令人满意的解释。它还解释了在存在大的心外膜动脉狭窄时发生的血流舒张 - 收缩期振荡的衰减。可变弹性模型表明，收缩期血流减少的程度取决于心肌收缩力，而不是取决于收缩时心室产生的压力。然而，虽然心室收缩压对壁厚相对较厚的心脏中的血流没有影响，但它会导致壁厚相对较薄的心脏中血流在收缩期减少。由于一种涉及冠状动脉容量的机制，收缩也决定了舒张期冠状动脉血流的水平。
