Biostability of thoralon left ventricular assist device blood pumping sacs after long-term clinical use

The purpose of this paper is to investigate the biostability of Thoralon polyurethane blood pumping sacs that have been used for up to 14 months in the Thoratec ventricular assist device (VAD) in human subjects. Thoralon is a proprietary polyetherurethaneurea (PEUU) blended with siloxane based surface modifying additive (SMA). Samples of Thoralon blood sacs that were used in Thoratec LVAD pumps for 53, 171, 336, and 434 days were taken from three distinct regions identified as high flex, medium flex, and low flex for physicochemical analysis. Explanted samples exhibited a slight but not significant increase in physical properties. The molecular weight of the blood sacs had also increased significantly in all blood sacs regardless of duration of use. SEM images did not indicate any cracking, pitting, or surface erosion; however, in a small area of the high flex region of the 336 day sac some biofilm was seen. The Attenuated Total Reflectance Fourier Transform Infra Red Spectroscopy (ATR-FTIR) analysis showed no significant reduction of surface ether content. The surface chemistry analyzed using Electron Spectroscopy for Chemical Analysis (ESCA) also indicated no significant change compared with control. These results confirm the biostability of Thoralon for long-term clinical applications in the Thoratec VAD.