Neovascularization in intimal hyperplasia is associated with vein graft failure after coronary artery bypass surgery

Vein graft atherosclerosis is the major limitation of arterial bypass surgery. This study was carried out to determine if the number of microvessels per area of intimal hyperplasia correlated with vein graft disease. Vein grafts (n=24, graft age range 2-19 years) were taken from 22 patients undergoing redo-coronary artery bypass surgery. Mean age of the patients was 68 ± 9 years; 92% were males. Samples were divided into three groups (n=8 per group): in group I segments were from grafts without angiographic or histologic disease, in groups II and III segments were from grafts with significant angiographic stenosis, without (group II) and with (group III) atheroma. Intimal hyperplasia was identified by Masson staining, morphometric analysis was performed with NIH image analysis software. Microvessels in the intimal hyperplasia were identified using immunohistochemical techniques. Significance was determined by single-factor ANOVA p < 0.05. The mean area of intimal hyperplasia was similar in groups I and II at 1.06 ± 0.25mm² and 0.97 ± 0.37 mm², respectively. The extent of intimal hyperplasia was significantly greater in group III, 1.70 ± 0.62mm² (p < 0.01). In group I, the microvessel count in the intimal hyperplasia was 5.62 ± 3.89 vessels/mm², while in group III it was 15.26 ± 3.66/mm² (p < 0.01 versus group I). Interestingly the number of microvessels per area of intimal hyperplasia in group II was similar to that in group III). In this study, the extent of neovascularization in intimal hyperplasia correlated with stenoses in human vein grafts. Strategies designed to limit neovascularization in intimal hyperplasia may lead to novel therapies to prevent vein graft failure.