Impact of coronary vasa vasorum functional structure on coronary vessel wall perfusion distribution

Noncoronary vasa vasorum have been described as networks of microvessels in the wall of arteries and veins. However, we have shown, using microcomputerized tomography (microCT) imaging methods, that porcine coronary vasa vasorum have a tree-like branching structure similar to the vasculature in general. In this study, we elucidate functional aspects of coronary vasa vasorum perfusion territories. Three pig hearts were injected with radiopaque Microfil via the coronary sinus to fill the left anterior descending coronary arteries (LADs) retrogradely at atmospheric pressure. In three other hearts, LADs were injected antegradely at 100-mmHg pressure via the left main carotid artery. Additionally, six LADs were injected in vivo with a suspension of 100- or 300-mum-diameter microspheres before harvesting of the hearts and injection of the LADs with Microfil. All harvested LADs were scanned intact with micro-CT (20 mum cubic voxels). The spatial density of vasa vasorum (no. of vasa/mm(2)) was measured in 20-mum-thick cross sections (at 0.4- mm intervals). Retrogradely injected LADs showed high and uniformly distributed vasa vasorum densities in the adventitia (means +/- SE; 5.38 +/- 0.09 vs. 3.58 +/- 0.1 vasa/ mm(2) in antegradely prepared LADs; P < 0.001). Antegradely prepared LADs showed patchy distributed, low-vasa-vasorumdensity territories especially on the myocardial side of the coronary artery wall ( epicardial density: 4.29 +/- 0.13 vasa/ mm2 vs. myocardial density: 2.80 +/- 0.1 vasa/mm(2), P < 0.001). Microembolization reduced vasa vasorum densities significantly (100-mum-diameter microspheres: 3.26 +/- 0.07 vasa/mm(2), P < 0.05; 300-mu m-diameter microspheres: 2.66 +/- 0.07 vasa/mm(2), P < 0.001 vs. antegrade controls) and increased the size of low-vasa-vasorum-density territories. We conclude that coronary vasa vasorum are functional endarteries not connected via a plexus. This characteristic may have a significant impact on the spatial distribution of perfusion and drainage of the coronary vessel wall.