Detrimental effects of mechanical stretch on smooth muscle function in saphenous veins

ObjectiveThis study evaluated the smooth muscle functional response and viability of human saphenous vein (HSV) grafts after harvest and explored the effect of mechanical stretch on contractile responses of porcine saphenous vein (PSV).MethodsThe contractile responses (stress, 105 N/m2) of deidentified, remnant HSV grafts to depolarizing potassium chloride and the agonist norepinephrine were measured in a muscle organ bath. Cellular viability was evaluated using a methyl thiazole tetrazolium (MTT) assay. A PSV model was used to evaluate the effect of radial, longitudinal, and angular stretch on smooth muscle contractile responses.ResultsContractile responses varied greatly in HSV harvested for autologous vascular and coronary bypass procedures (0.04198 ± 0.008128 × 105 N/m2 to 0.1192 ± 0.02776 × 105 N/m2). Contractility of the HSV correlated with the cellular viability of the grafts. In the PSV model, manual radial distension of ≥300 mm Hg had no impact on the smooth muscle responses of PSV to potassium chloride. Longitudinal and angular stretch significantly decreased the contractile function of PSV by 33.16% and 15.26%, respectively (P < .03).ConclusionsThere is considerable variability in HSV harvested for use as an autologous conduit. Longitudinal and angular stretching during surgical harvest impairs contractile responsiveness of the smooth muscle in saphenous vein. Avoiding stretch-induced injuries to the conduits during harvest and preparation for implantation may reduce adverse biologic responses in the graft (eg, intimal hyperplasia) and improve patency of autologous vein graft bypasses.Clinical RelevanceHuman great saphenous vein remains the most commonly used conduit for coronary artery bypass grafting and peripheral vascular revascularization. The techniques commonly used for surgical saphenous vein harvest can produce significant injury to the conduit and elicit an exuberant physiologic healing response in the vessel walls, leading to the development of intimal hyperplasia. Intimal hyperplasia is thought to involve smooth muscle proliferation, migration, phenotypic modulation, and extracellular matrix deposition, and ultimately, lead to graft occlusion. This study shows that mechanical stretching injures vascular smooth muscle and reduces contractile responsiveness of the saphenous vein. Thus, by understanding how these injuries can be minimized, mortality and costs associated with vein graft failure can be reduced.