Increased platelet deposition on polytetrafluoroethylene grafts after balloon catheter thrombectomy

Prosthetic graft rethrombosis after thrombectomy may be potentiated by increased thrombogenicity of the restored flow surface. This experiment compared platelet deposition on polytetrafluoroethylene (PTFE) grafts after balloon catheter thrombectomy with deposition on new, nonthrombosed grafts. Three models of graft thrombosis were studied in eight dogs with 4 mm diameter by 7 cm PTFE graft segments: (1) in vitro model: grafts filled with blood, stored in 37 degrees C saline solution; (2) in vivo model: blood-filled grafts stored in subcutaneous tissue; and (3) in situ model: one end of grafts anastomosed to femoral or carotid artery as a blind tube. Duration of thrombosis (1, 2, and 3 weeks) was studied by initiating one graft of each type per week in each dog. After 3 weeks, nine thrombosed grafts per dog were harvested and graft thrombectomy was performed with a 3F balloon catheter. An ex vivo flow-controlled perfusion circuit was then created in each dog and platelet deposition was measured during the initial 20 minutes of graft perfusion after 111In platelet labeling. Thrombectomized grafts were compared with new, control grafts not previously exposed to blood, as well as with grafts exposed for 1 hour to blood or plasma. Compared with control grafts, platelet deposition was significantly increased on in vivo (3.7 times control; p less than 0.01), in situ (2.6 times control; p less than 0.05), and in vitro thrombosed grafts (2.0 times control; p less than 0.05). Age of thrombus was not a significant source of variation. Blood or plasma exposure alone did not significantly increase platelet deposition. These data suggest that antiplatelet therapy may be important at the time of PTFE graft thrombectomy.