Intramyocardial vascular volume distribution studied by synchrotron radiation-excited X-ray fluorescence

We evaluated the vascular volume distribution with fine resolution (0.1-1.3 mg myocardial tissue) in the sagittal plane of the left ventricle by using the microsphere filling method in 21 dogs. The coronary arterial volume de nsity in the sagittal plane did not exhibit normal distribution and was cha racterized by variability among the outer-to-inner layers and within the la yers (+2SD/-2SD > 80 times), and the median values in the layers ranged fro m 4.7 to 22.9 nl/mg myocardial tissue. The fractal analysis of vascular vol ume revealed a self-similar nature with a fractal dimension (D value) simil ar to that of flow distribution (1.20 +/- 0.05 and 1.24 +/- 0.09 for vascul ar volume and flow distribution, respectively) and had a more marked variab ility than the flow The correlation of the regional vascular volume between adjacent regions decreased as the distance increased. However, the correla tion coefficients in the endocardial-to-epicardial direction were significa ntly higher than those in the anterior-to-posterior direction (P < 0.05 by paired t-test). In conclusion, we determined intramyocardial vascular volum e density in the sagittal plane, and the distribution revealed considerable variability, self-similarity, and asymmetry in the correlation among the a djacent regions. These observations could be related to the characteristics of the intramural coronary vascular network.