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Aim: We sought to determine variations in fiber organization at the molecular level using x-ray diffraction analyses on human blood vessel specimens after cryopreservation processes., Materials and Methods: Diffractometric profiles were performed on aortic and carotid cryopreserved-thawed vessel samples (CVS) versus the same fresh vessel samples (FVS). X-ray diffraction was performed on vascular tissues from 17 cadaveric donors after informed consent. Measurements utilized a Seifert Scintag PAD-II powder diffractometer with CuK(a) radiation; lambda = 1.5418 A. Scans were evaluated in the 5 degrees to 60 degrees range in theta -2theta mode, in the 5 degrees to 60 degrees range in 2-theta, with steps 0.1 degrees and 10 seconds per step. Ten aortic and 8 carotid diffractometric profiles were analyzed, using differential planimetric surfaces measured under x-ray diffraction curve. Diffractographic profiles were analyzed according to intervals based upon the ages of the donors. An ordering profile coefficient (OPC) was obtained as the quotient between the differential planimetric surface (DPS) of FVS versus CVS vessel ordering diffraction., Results: There was a decreased ordering profile according to age: older donors showed less ordering than younger ones. Clear peaks at d-spacing of 2.86 A and 2.15 A (2-theta = 31.3 degrees and 42.0 degrees , respectively) were always confirmed despite the different profiles of samples. OPC showed a higher ordering profile among the CVS than FVS: 70% aortas and 62.5% carotids., Conclusion: The cryopreserved-thawed procedure does not damage the fibrillar organization of vessels.

The aim of this study was to characterize and compare human great saphenous veins (HGSVs), HGSV cryoallografts, expanded polytetrafluoroethylene (ePTFE) segments, and elastic and muscular arteries' biomechanics, so as to identify if the biomechanical coupling and the HGSV advantages with respect to ePTFE depend on the arterial type and/or on the biomechanical property considered. Pressure and diameter were measured in vitro, under arterial hemodynamic conditions, in elastic and muscular arteries, and in vascular substitutes: fresh and cryopreserved HGSV and ePTFE segments. The wall's dynamics (compliance, viscosity, and inertia), energy dissipation, and buffering were calculated. The coupling was quantified for each biomechanical parameter. Cryopreservation preserved HGSV biomechanics. The HGSV cryoallografts' dynamics, energetics, and buffering were lesser with respect to both arteries, but were higher than the ePTFE. The coupling differed, depending on the arterial type and property considered. The biomechanical coupling depended on the artery and property considered. HGSV cryoallograft advantages over ePTFE were arterial type and property independent.

Introduction and Objectives: It is not yet known whether cryopreservation enables vessels to retain their viscoelastic properties or whether cryopreserved homografts are biomechanically more like native arteries than currently used vascular prostheses. The study objectives were: a) to determine whether our cryopreservation methodology enables arterial and venous homografts to retain their viscoelastic and functional properties; and b) to assess similarities between patients' femoral arteries, homografts, and other vascular prostheses in common use., Methods: The pressure and the diameter and parietal thickness of 15 muscular (femoral) arteries were measured in patients using tonometry and echography, both noninvasive techniques. In addition, the pressure in and diameter and parietal thickness of 15 fresh and 15 cryopreserved human muscular (femoral) artery segments, saphenous veins, and 15 expanded polytetrafluoroethylene (ePTFE) vascular prostheses were measured in vitro under hemodynamic conditions similar to those in patients. A Kelvin-Voigt model of the segment wall was used to derive elastic (Epd, mm Hg/mm) and viscous (Vpd, mm Hg x s/mm) pressure-diameter indices, the buffering function (Vpd/Epd), and the conduit function (1/Zc, where Zc is the characteristic impedance). The incremental Young modulus, the pressure-strain elastic modulus, and pulse wave velocity were also calculated., Results: No difference was observed between either the viscoelastic or functional properties of fresh and cryopreserved homografts. Arterial homografts were the most similar to the patient's arteries., Conclusions: Cryopreservation enabled venous and arterial homografts to retain their viscoelastic and functional properties. Of all the grafts investigated, arterial homografts were most similar, both biomechanically and functionally, to the patient's femoral arteries.

Introduction: The prosthesis nowadays used in the vascular access for haemodialysis have low patency rates, mainly due to the luminal obstruction, determined by the intimal hyperplasia. Several factors have been related to de development of intimal hyperplasia and graft failure. Among them are the differences in the biomechanical properties between the prosthesis and the native vessels. In the searching for vascular prosthesis that overcomes the limitations of the currently used, the cryopreserved vessels (cryografts) appear as an alternative of growing interest. However, it is unknown if the mechanical differences or mismatch between prosthesis and native vessels are lesser when using cryografts., Objective: To characterize and compare the biomechanical behaviour of native vessels used in vascular access and cryografts. Additionally, segments of expanded polytetrafluoroethylene (ePTFE) were also evaluated, so as to evaluate the potential biomechanical advantages of the cryografts respect to synthetic prosthesis used in vascular access., Methods: Segments from human humeral (n = 12), carotid (n = 12) and femoral (n = 12) arteries, and saphenous vein (n = 12), were obtained from 6 multiorgan donors. The humeral arteries were studied in fresh state. The other segments were divided into two groups, and 6 segments from each vessel were studied in fresh state, while the remaining 6 segments were evaluated after 30 days of criopreservation. For the mechanical evaluation the vascular segments and 6 segments of ePTFE were mounted in a circulation mock and submitted to haemodynamic conditions similar to those of the in vivo. Instantaneous pressure (Konigsberg) and diameter (Sonomicrometry) were measured and used to calculate the viscous and elastic indexes, the compliance, distensibility and characteristic impedance. For each mechanical parameter studied, the mismatch between the prosthesis and the native vessel was evaluated., Results: The ePTFE was the prosthesis with the higher mechanical mismatch (p < 0.05). The venous and arterial cryografts showed the least mismatch with native veins and arteries, respectively. The prosthesis with the least mechanical mismatch was different, depending on the native vessel evaluated, and for a native vessel, on the parameter considered., Conclusion: The mechanical mismatch between the native vessel and the vascular prosthesis used in a vascular access could be reduced using cryografts.