AJP - Heart and Circulatory Physiology, Vol 257, Issue 4 1076-H1081, Copyright © 1989 by American Physiological Society
Hydrostatic pressure reduces thrombogenicity of polytetrafluoroethylene vascular grafts
E. F. Ritter, R. D. Vann, C. Wyble, W. J. Barwick and B. Klitzman
Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710-3906.
A prime factor in the thrombogenicity of synthetic materials in contact
with blood is the blood-gas interface. Small pockets of gas, known as gas
nuclei, are trapped within surface interstices. The resulting blood-gas
interface denatures plasma proteins and activates clotting factors and
platelets. Expanded polytetrafluoroethylene (ePTFE) vascular prostheses 1
mm in internal diameter were placed in saline under 6,000 psig hydrostatic
pressure for 2 h in an attempt to dissolve all gas nuclei (i.e., to
denucleate). Carotid-carotid bypasses were performed in rats using 280-mm
lengths of ePTFE. All 10 control grafts lost patency in 5 min, whereas the
14 denucleated grafts had a median patency duration of 300 min (P less than
0.01). In 15-mm-long rat femoral artery interpositional ePTFE grafts, 90%
of controls thrombosed within 10 min, whereas only 7% of denucleated grafts
thrombosed over the duration of the 7-day observation period (P less than
0.001). Denucleation also resulted in a significant reduction (P less than
0.02) in 111In-labeled platelet adhesion to 36% of control. Scanning
electron microscopy confirmed the reduced accumulation of platelets on
denucleated grafts. These data suggest that the removal of trapped air with
hydrostatic pressure significantly reduces the thrombogenicity of ePTFE
microvascular prostheses and may have application to other clinical
(catheters, valves, tubing, etc.) or experimental (micropipettes,
electrodes, etc.) materials that interface with blood.
