The study will examine the results of the use of biological materials (allogeneic arterial grafts, allogeneic venous graft, autologous vein, biological bovine decellularized graft) as a bypass grafts for reconstructive interventions in patients with critical lower limb ischemia due to atherosclerotic peripheral arterial disease in the short-term and long-term postoperative periods. Histological analysis of allogeneic grafts will be carried out at various time points of graft preservation with a Roswell Park Memorial Institute 1640 cell medicum with 400mcg/ml gentamicin and 20mcg/ml fluconazole at a temperature of +4C.

The physical properties of allogeneic grafts from postmortem donors (tensile and tear strength) will be evaluated at various conservation time periods (1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks). Markers of endothelial dysfunction (IL-6, endothelin-1, 6-keto-prostaglandin F1alfa, eNOS) will be evaluated in patients with critical ischemia who undergo bypass procedures with arterial and venous allografts at various time points (before surgery, 7 days, 1 month, 3 months, 6 months, 1 year after).

The study will include 200 patients of similar age, gender, and ethnicity, who will be divided into four groups:

Group I: 50 patients who undergo arterial bypass procedures using autologous venous graft derived from great saphenous vein; Group II: 50 patients who undergo arterial bypass procedures using allogeneic venous grafts; Group III: 50 patients who undergo arterial bypass procedures using allogeneic arterial grafts; Group IV: 50 patients using biological bovine decellularized grafts.

Patients will be monitored for 2 years: at inclusion, and 1, 3, 6, 12, 18, and 24 months after bypass procedures.

The primary endpoint of the study will be mortality, i.e. death of the patient from any cause. Secondary endpoints of the study will be graft thrombosis and cardiovascular events such as myocardial infarction, acute coronary syndrome, transient ischemic attack, and stroke.

Inclusion Criteria:

• males or females over 18 years of age;
• critical lower limb ischemia due to atherosclerotic peripheral arterial disease.

Exclusion Criteria:

• males or females less than 18 year of age;
• decompensated concomitant pathology;
• pregnancy or lactation.