EFFECT OF VASA VASORUM FLOW ON STRUCTURE AND FUNCTION OF THE AORTA INEXPERIMENTAL-ANIMALS

Background It is known that vasa vasorum flow contributes substantiall y to the nutrition of the outer layers of the thoracic aorta. This inv estigation was undertaken to test the hypothesis that impairment of va sa vasorum flow would alter the structure of the aortic wall and chang e the elastic properties of the aorta. Methods and Results The periaor tic fat that contains the vasa vasorum for the ascending aorta was rem oved in seven anesthetized dogs, and the results were compared with th ose obtained from six weight-matched sham-operated control dogs. Aorti c pressures, aortic diameters, and aortic distensibility were obtained before and 30 minutes and 15 days after removal of the periaortic vas a vasorum network. Aortic pressures were measured directly with a flui d-filled catheter. Aortic diameters were measured simultaneously with aortic pressures with an elastic, air-filled ring connected to a trans ducer. Aortic distensibility was calculated by the formula 2Xpulsatile change in aortic diameter/(diastolic aortic diameterXpulse pressure). Histology was performed in transverse blocks of aortic wall at the en d of the experiment in both groups. The efficacy of the technique for the interruption of vasa vasorum blood supply to the aortic wall was d emonstrated by histology in four additional animals that were killed w ithout removal of vasa vasorum (two animals) and immediately after vas a vasorum removal (two animals). At baseline, heart rate, aortic press ures, aortic diameters, and aortic distensibility were similar in the two groups. A significant decrease in aortic distensibility was observ ed 30 minutes and 15 days after removal of the vasa vasorum in the exp erimental group (baseline, 3.453+/-1.023; 30 minutes, 2.521+/-0.760; 1 5 days, 1.586+/-0.488 10(-6) . cm(2) . dyn(-1); F=9.532, P<.001). No c hanges were observed in aortic distensibility in the control group dur ing the experiment. Histology of the aorta revealed medial necrosis, a lterations of the elastin fibers, and a trend (P=.055) for altered col lagen-to-elastin ratio in a region occupying more than the one (outer) half of the media of the experimental group animals. No changes were observed in the control group. Conclusions The findings of the present study demonstrated that interruption of vasa vasorum flow led to an a cute decrease in the distensibility of the ascending aorta. Moreover, structural changes of the aortic wall and further deterioration of the elastic properties of the aorta occurred 15 days after vasa vasorum r emoval.