Viscoelastic properties of the autologous bypass grafts: A comparative study among the small saphenous vein and internal thoracic artery

Internal thoracic artery (ITA) and small saphenous vein (SSV) are two viable conduits for coronary artery bypass grafts. The aim of this study was to investigate the viscoelastic behavior of the small saphenous vein and internal thoracic artery under compressive and tensile loadings at body temperature. The dynamic mechanical analysis was used to measure the viscoelastic properties of the ITA and SSV at both the desired temperature and load frequency range. Storage modulus, loss modulus as well as phase angle of both the blood vessels were measured at the temperature of 37 ± 1 °C and under a sinusoidal load with the frequency range of 1-2 Hz. The mean storage and loss modulus of the SSV were both higher than that of the ITA. Furthermore, the SSV showed a higher stiffness and internal friction compared to those values under the tensile load. While ITA was stiffer under the tensile load, no considerable difference was observed among the compressive and tensile loss modulus. A more intense viscous behavior was observed under the radial direction. The results also revealed that the SSV has much higher stiffness whereas less viscous behavior compared to the ITA, especially in the radial direction. The results may have implications not only for understanding of the viscoelastic time-dependent mechanical behavior of the ITA and SSV but also for tissue engineering applications to make scaffolds according to the real time-dependent viscoelastic mechanical properties of these arteries and veins.