Vasa vasorum of the failed aorto-coronary venous grafts

This study was designed to investigate the distribution of vasa vasorum in walls of failed aorto-coronary venous grafts. Fifty-one diseased venous grafts harvested from 39 patients underwent qualitative histological evaluation. The morphology of the grade of the pathological changes and the extent of the vascularisation were examined, and related to the length of the interval between the primary surgery and the explantation. The obtained results were placed into five groups, substantially differing one from the other in morphology and vascularisation. The intervals between grafts implantation and explantation ranged from 1 day to 35 years. The onset of arterialization of the graft media was observed on average at 1 month after bypass implantation. During this same time period massive intimal hyperplasia and atherosclerosis occurred. Vasa vasorum proliferation from the adventitia to the outer layers of the media was first apparent between 7 and 24 months after implantation. Proliferation of the vasa vasorum throughout the entire atherosclerotic media and hyperplastic intima continued for a much longer time interval. No correlation between neoangiogenesis and age, sex or type of bypassed coronary branch was proven. Regarding the given findings, the authors believe that changes in hemodynamic conditions and endothelial trauma are primarily responsible for the development of graft disease and that vasa vasorum proliferation is only a secondary reaction to the structural changes of the graft wall. To what extent the frequently present pre-existing intimal hyperplasia of venous bypass grafts play in the development of graft disease remains questionable.