An acute canine ex-vivo femoral A-V shunt technique was used to study
thrombus formation and embolization on a number of porous and non-porous
polymer surfaces over a one-hour blood contact period. The technique allows for simultaneous exposure of all the surfaces under similar physiological and hematological conditions. This makes comparisons between surfaces more reliable. SEM was used to study changes in the morphology of platelets and thrombi present on the
polymer surfaces. Quantitative information was obtained using radiolabeled platelets. In general, platelet deposition, activation, and aggregation was followed by
thrombus formation which peaked at about 15-30 minutes of blood contact. Thrombi were composed mainly of platelets with few leukocytes present. Embolization was observed on
Silastic (SIL), polyvinylchoride (
PVC),
polyethylene (PE), and oxidized
polyethylene (OX-PE) surfaces between 20 and 60 minutes of blood contact. The mechanism for embolization involved clot retraction under the influence of a shear field. Leukocytes did not appear to be necessary for the initiation of embolization but were present during the embolization phase on OX-PE, possibly due to
chemotactic factors. Although extensive
thrombus formation was observed on the porous
PTFE materials (GORE-TEX and
IMPRA), the thrombi formed were flat and did not significantly block the lumen. By 60 minutes of blood contact, only minimal embolization had occurred on the
PTFE surfaces. SEM examination of the sequence of
thrombus formation and embolization was found to correlate well with trends in platelet deposition measured using radiolabeling techniques.