INFLUENCE OF TWIST ON VEIN AND PTFE GRAFT HEMODYNAMICS - AN EX-VIVO EXPERIMENTAL-STUDY

Objective. In an ex vivo infusion model, the effect of different facto rs affecting the critical level of twist in vein and PTFE grafts was a nalysed, Setting, University Hospital, Department of Surgery, Experime ntal design, Saline perfusion of grafts with various diameter and leng th under constant high (90 ml/min) and low (50 ml/min) flow rates agai nst various peripheral resistance was performed, Measures, The pressur e changes in the grafts were measured at increasing increments of twis ting, Results, The critical level of twist appears to be dependent on the diameter, length, stretching, status of peripheral resistance, amo unt of volume flow and the type of graft material, varying between 90 to more than 360 degrees, In vein grafts critical twisting appeared ea rlier with a decrease in diameter, shortening in length, high peripher al resistance, high flow rate and stretching, PTFE grafts especially w ith external spiral support were resistant to twist, Conclusions. Thes e data suggest that the critical level of graft twist is dependent upo n multiple factors and moderate or even high grade twist with especial ly externally supported PTFE grafts regardless of length and long mobi lized vein grafts do not lead to hemodynamic changes. On the other han d total cessation of flow occurs at lower degrees of twist in stretche d, short vein grafts.