Histological and biochemical characteristics of arteries and veins in patients candidate for coronary bypass surgery

The occlusion of the artery and vein grafts are currently a major problem in coronary bypass surgery. Degradation of collagen and elastin, the most abundant extracellular matrix proteins in the vessel wall by matrix metalloproteinase (MMPs), leads to a rearrangement of the extracellular matrix and vascular wall structure. The present study aimed to compare the histological and biochemical characteristics of arteries and veins which could have a role in the failure of the graft.

This study was a cross-sectional study of 80 patients conducted at Heart Hospitals in Isfahan, Iran, between July 2012 and November 2013. Samples were collected from the remains of vessels used in bypass surgery of 11 male nondiabetic patients. The histologic, collagen elastin ratio and MMPs levels of the vessels were investigated. MMPs were determined using the Gelatin Zymography method. For elastin and collagen content measurement, the sample was digested by cyanogen bromide and hydrochloric acid and then hydroxyproline was measured with a spectrophotometer.

The amount of active and inactive MMP-2 and MMP-9 of the left internal mammary artery (Lima) was similar to aorta, but the amount of MMP-2 and MMP-9 in the radial artery and saphenous vein were significantly higher than aorta. Elastin to collagen ratio in Lima (1.92±1.15) was similar to the aorta (3.4±1.66), but this proportion in saphenous vein (1.07±0.47) and radial artery (1.14±0.39) was significantly lower in the aorta (P≤0.05). Most patients had atherosclerotic plaque in radial while there was atherosclerotic plaque in Lima of only one case.

The presence of atherosclerotic plaques in radial and thickening of the intimal layer of the saphenous vein in the majority of patients and decrease of collagen to elastin ratio and the high level of matrix metalloproteinase enzymes in the radial and saphenous vein can induce early pathological conditions, and remodeling of the vessels involved. So the results of this study confirm that Left Internal Mammary Artery (LIMA) is the most suitable candidate for bypass surgery.