Kalsho Ghada, Kassab Ghassan S
Dept. of Biomedical Engineering, Univ. of California-Irvine, 204 Rockwell Engineering Center, Irvine, CA 92697-2715, USA.
Am J Physiol Heart Circ Physiol. 2004 Dec;287(6):H2493-500. doi: 10.1152/ajpheart.00371.2004.
The branching pattern of the coronary arteries and veins is asymmetric, i.e., many small vessels branch off of a large trunk such that the two daughter vessels at a bifurcation are of unequal diameters and lengths. One important implication of the geometric vascular asymmetry is the dispersion of blood flow at a bifurcation, which leads to large spatial heterogeneity of myocardial blood flow. To document the asymmetric branching pattern of the coronary vessels, we computed an asymmetry ratio for the diameters and lengths of all vessels, defined as the ratio of the daughter diameters and lengths, respectively. Previous data from silicone elastomer cast of the entire coronary vasculature including arteries, arterioles, venules, and veins were analyzed. Data on smaller vessels were obtained from histological specimens by optical sectioning, whereas data on larger vessels were obtained from vascular casts. Asymmetry ratios for vascular areas, volumes, resistances, and flows of the various daughter vessels were computed from the asymmetry ratios of diameters and lengths for every order of mother vessel. The results show that the largest orders of arterial and venous vessels are most asymmetric and the degree of asymmetry decreases toward the smaller vessels. Furthermore, the diameter asymmetry at a bifurcation is significantly larger for the coronary veins (1.7-6.8 for sinus veins) than the corresponding arteries (1.5-5.8 for left anterior descending coronary artery) for orders 2-10, respectively. The reported diameter asymmetry at a bifurcation leads to significant heterogeneity of blood flow at a bifurcation. Hence, the present data quantify the dispersion of blood flow at a bifurcation and are essential for understanding flow heterogeneity in the coronary circulation.
冠状动脉和静脉的分支模式是不对称的，即许多小血管从一个大主干分支出来，使得分叉处的两个子血管直径和长度不相等。这种几何血管不对称的一个重要影响是分叉处血流的分散，这导致心肌血流的大空间异质性。为了记录冠状动脉的不对称分支模式，我们计算了所有血管直径和长度的不对称比，分别定义为子血管直径和长度的比值。分析了先前来自包括动脉、小动脉、小静脉和静脉在内的整个冠状动脉系统的硅橡胶铸型数据。较小血管的数据通过光学切片从组织学标本中获得，而较大血管的数据从血管铸型中获得。根据每个母血管级别的直径和长度不对称比，计算各个子血管的血管面积、体积、阻力和血流的不对称比。结果表明，最大级别的动脉和静脉血管最不对称，并且不对称程度朝着较小血管降低。此外，对于2 - 10级血管，冠状动脉分叉处的直径不对称性（窦静脉为1.7 - 6.8）比相应动脉（左前降支冠状动脉为1.5 - 5.8）明显更大。报道的分叉处直径不对称导致分叉处血流的显著异质性。因此，本数据量化了分叉处血流的分散，对于理解冠状动脉循环中的血流异质性至关重要。
