A functional and histopathological comparison of proximal and distal saphenous vein contractility and morphology

Abstract

Variations in vascular reactivity and morphology of proximal and distal saphenous vein might affect its performance as a bypass conduit. Because peri- or postoperative graft spasm or intimal hyperplasia reduces patency, we compared the reactivity and morphology of human proximal and distal saphenous vein conduits. Isometric tension studies were performed in response to potassium chloride (80 mM), phenylephrine (10(-8) - 10(-5) M), norepinephrine (10(-8) - 10(-5) M), and angiotensin II (10(-11) - 10(-7) M). Relaxant responses were tested with acetylcholine (10(-9) - 10(-5) M), sodium nitroprusside (10(-10) - 10(-6) M), and diltiazem (10(-10) - 10(-4) M). Also, vein segments from proximal and distal leg saphenous vein grafts were collected for histopathologic investigation. In proximal and distal saphenous vein segments, we also examined the structure of intima, media, and adventitia, and we evaluated the smooth muscle cell/extracellular matrix ratio in the media. There was no significant difference (P > 0.05) between proximal and distal venous segments in response to vasoconstrictors or vasodilators. Similarly, investigation by light microscopy was unable to show any significant difference between proximal and distal conduits in vascular structure. The smooth muscle cell/extracellular matrix ratio was also similar in these graft materials. Our failure to find functional or morphologic differences between proximal and distal saphenous vein segments suggests that there is no advantage in using one of these preparations over the other as a conduit in coronary artery bypass operations.

Fig. 1 Contractile effect of 80-mM KCl on proximal and distal saphenous vein segments (n = 7 for all groups). Values are mean ± SEM.

Fig. 2 Contractile responses to norepinephrine (A), phenylephrine (B), and angiotensin II (C) in the proximal and distal saphenous vein segments (n = 7–8 for all groups). Values are mean ± SEM.

Fig. 3 Effects of acetylcholine (A), sodium nitroprusside (B), and diltiazem (C) on the tone of isolated human proximal and distal saphenous vein that had been contracted with phenylephrine (n = 14 for all groups). Agonists were added cumulatively after reaching a stable contraction. Values are mean ± SEM.

Fig. 4 Thickness of intima and media (A), and smooth muscle cell/extracellular matrix (SMC/ECM) ratio (B) of proximal and distal saphenous vein segments (n = 7 for all groups). Values are mean ± SEM.