Peculiarities of biomechanical behavior of human varicose veins

Endovenous surgery nowadays is a common practice, leaving vascular surgeons in selected cases (radical venous surgery in patients with peripheral and coronary occlusive disease) with no venous grafts for possible future arterial bypass surgery. The aim of this study was to investigate the biomechanical properties of human varicose veins, and provide recommendations for the extent of future venous surgery. Taking into considerations many variables, patients were divided according to duplex ultrasonography data into three main groups (sever venous reflux > 2 seconds, group A; moderate venous reflux < 2 seconds, group B, and control group, no reflux, group C). Variants such as gender, vein location (above or below knee level), standing vein diameter and, disease severity (according to Clinical, Etiological, Anatomical, and Pathophysiological (CEAP) classification) were registered. At the laboratory, a special experimental load-standing bench with a video camera connected to a computer measured venous internal pressure, and external diameter. During the experiments, vein samples were gradually loaded with saline solution (NaCl 0.9%), raising their internal pressure from 0 to 200 mmHg while maintaining the length of vein specimens constant. Venous internal pressure was increased gradually by 20 mmHg increments, holding it constant at each step for 1 minute. Vein specimens, thus, stretched at their in situ length. Stress, strain and incremental modulus of elasticity in venous wall calculated at each experimental point. Results show that stress – strain relationship is non-linear. Venous diameter increases rapidly until internal pressure reaches 40 mmHg, and any further increase in internal pressure leads to an increase in vein wall stiffness and modulus of elasticity. Further evaluation of biomechanical properties of varicose vein segments and comparison of these properties with the properties of arterial specimens will assess the possibility of using multiple vein segments at least sutured end-to-end as arterial bypass grafts.