Twist Buckling of Veins

Twisted or tortuous veins are often associated with cardiovascular diseases such as hypertension and diabetes, yet the mechanisms responsible for tortuosity progression remain unclear.  Previously, our lab has shown that veins will lose stability and buckle when subject to increased lumen pressure or reduced axial tension.  However, veins can also undergo twist deformations with body movement and vascular surgeries.  Yet, little data is available regarding the stability of veins under torsion.  Therefore, it is of clinical interest to investigate the mechanical stability of veins under torsion.  The goal of this work was to experimentally investigate the buckling behavior of veins under torsion and determine the critical buckling torque, rotation angle, and buckling shape.  We tested porcine internal jugular veins using a custom-built machine which could generate combined axial tension, lumen pressure, and torsion.  Veins were initially loaded to various combinations of axial tension and lumen pressures similar to in vivo values.  Then, the distal end of the vein was slowly rotated until buckling occurred.  The results demonstrated that veins will buckle into a kinked configuration when subject to torsion.  Torque increased with rotation but dropped suddenly upon vessel buckling.  The critical values were identified at this point of instability.  Understanding the twist behavior of veins will help elucidate the link between torsion and the development of vein tortuosity.  This information will also provide guidance for improved vascular graft design and surgical techniques.  These results further our knowledge of vascular mechanics and may help to identify risk factors for venous diseases.