Study of the functional properties and thrombogenicity of vascular xenografts after long-term storage

Background. Reconstructive interventions on major blood vessels remain among the most challenging issues in contemporary vascular surgery. Consequently, clinical practice shows growing interest in biological vascular grafts, particularly allografts and xenografts, which exhibit superior biocompatibility and a greater potential for integration into recipient tissues. Purpose – to evaluate the functional suitability of xenogeneic vascular prostheses after 24 months of cryopreservation, with a comprehensive assessment of cardiovascular status and thrombogenic potential in an experimental rabbit model. Materials and Methods. Experimental studies were performed on 28 Chinchilla rabbits weighing 3200–4500 g. Cryoradiation-treated segments of the porcine a. thoracica interna were used as vascular prostheses after 2 years of preservation in liquid-nitrogen vapor. Implantation of vascular grafts measuring 2–7 cm in length was carried out in the abdominal segment of the rabbitsʼ aorta, proximal to the aortic bifurcation. Sonographic examination of the vasculature, including the abdominal aorta, was conducted with a «Sonomed 500» ultrasonic echotomograph (manufacturer: «Spectromed», Ukraine) in BD-mode using a 7.5 L38 linear probe operating at a frequency of 7.5 MHz. Cardiac evaluation was performed in both B- and M-modes. For assessment of blood coagulation parameters, the following were measured: prothrombin time, international normalized ratio (INR), activated partial thromboplastin time (aPTT), thrombin time, and plasma fibrin concentration. Results. Vascular xenografts after prolonged storage demonstrated good functionality, absence of thrombogenicity, and adequate integration. Despite variation in the length of the transplanted prostheses (2–7 cm), no acute thrombosis or clinically significant stenotic changes were detected in any of the animals. Over a 360‑day period, the xenograft diameter increased by 19%, reaching 3.8 ± 0.2 mm, while blood flow velocity within the graft decreased by 25% (51.7 ± 7.6 cm/s), with a pulsatility index (PI) of 1.32 ± 0.24. These findings confirm the absence of critical dilatation or stenosis, although the formation of a minor aneurysmal enlargement remains possible. Hemodynamic parameters during the year following vascular graft transplantation remained stable, with no pathological changes detected in the heart or vasculature. At all observation points (days 30, 180, 360), left ventricular indices – including chamber diameters, wall thicknesses, heart rate, ejection fraction (EF), and fractional shortening (FS) – remained within normal limits, with no evidence of dilatation. Hematologic test results revealed a transient coagulopathy with complete normalization by days 14–30, indicating restoration of hemostasis. At 180–360 days, all coagulation parameters did not differ from normal values, confirming a compensatory response of the coagulation system and showing no signs of cardiac hypertrophy, dysfunction, or overload. Conclusions. The study demonstrated high biocompatibility and stable functional properties of vascular xenografts following 24 months of cryopreservation. The prostheses provided adequate blood flow without thrombosis or critical stenosis, preserved morphological integrity, and induced no pathological changes in the cardiovascular system during one year of observation. Hemodynamic parameters and myocardial function remained within physiological limits, while transient coagulation disturbances returned to baseline values within the first month. These findings confirm the promise of such xenografts for application in reconstructive vascular surgery.