Lindner J R, Skyba D M, Goodman N C, Jayaweera A R, Kaul S
Cardiovascular Division, University of Virginia School of Medicine, Charlottesville 22908, USA.
Am J Physiol. 1997 Jan;272(1 Pt 2):H567-75. doi: 10.1152/ajpheart.1997.272.1.H567.
Vasodilation of microvessels distal to a stenosis results in an increase in myocardial blood volume (MBV). The purpose of this study was to examine the changes in MBV induced by graded coronary artery stenoses by using myocardial contrast echocardiography (MCE). Accordingly, 21 dogs underwent progressive stenosis of a coronary artery in a random order, the severity of which was judged by the pressure distal to it. Total myocardial blood flow (MBF) to the bed distal to the artery (both anterograde and collateral) was measured by injection of radiolabeled microspheres into the left atrium. In seven dogs, anterograde and total MBF were measured at each stenosis stage by injection of different microspheres into the left atrium and directly into the coronary artery, respectively. MBV was calculated by dividing MBF by the mean transit rate of microbubbles injected directly into the coronary artery during MCE. The perfusion bed size of the artery was also measured by MCE. Our major findings are as follows: 1) there is a nonlinear increase in MBV with increasing degrees of coronary stenosis until the coronary stenosis becomes critical; 2) at moderate levels of coronary stenosis, MBV remains constant despite ongoing autoregulation because of reduction in the size of the perfusion bed supplied by the stenotic vessel; and 3) after exhaustion of autoregulation, a decrease in MBV is noted with increasing levels of stenosis. We conclude that assessment of MBV provides insights into myocardial perfusion distal to a coronary stenosis above and beyond that provided by the measurement of MBF alone.
狭窄远端微血管的血管舒张会导致心肌血容量（MBV）增加。本研究的目的是通过心肌对比超声心动图（MCE）检查分级冠状动脉狭窄引起的MBV变化。因此，21只犬随机接受冠状动脉的渐进性狭窄，其严重程度通过其远端压力判断。通过向左心房注射放射性标记微球来测量动脉远端心肌床的总心肌血流量（MBF）（包括顺行和侧支）。在7只犬中，通过分别向左心房和直接向冠状动脉注射不同的微球，在每个狭窄阶段测量顺行和总MBF。MBV通过将MBF除以MCE期间直接注入冠状动脉的微泡平均通过速率来计算。动脉的灌注床大小也通过MCE测量。我们的主要发现如下：1）随着冠状动脉狭窄程度的增加，MBV呈非线性增加，直到冠状动脉狭窄变得严重；2）在中度冠状动脉狭窄水平时，尽管存在自动调节，但由于狭窄血管供应的灌注床大小减小，MBV保持恒定；3）自动调节耗尽后，随着狭窄程度的增加，MBV会降低。我们得出结论，对MBV的评估为冠状动脉狭窄远端的心肌灌注提供了单独测量MBF之外的深入了解。
