Radionuclide Study of Platelets and Prosthetic Interactions: External Versus Specimen Quantitation

Abstract

Twenty-nine New Zealand white rabbits were allocated to undergo insertion of either polytetrafluoroethylene (PTFE) (n = 22) or microporous silicone rubber (SR) (n = 7), 3-mm diameter, 10-mm long aortic grafts. Animals with PTFE grafts received aspirin (ASA) 10 mglkgld and dipyridamole (DPM) 10 mglkgld (n = 11) or placebo (n = 11). Autologous In-111-oxine-labeled platelets were reinfused on reestablishment of blood flow through the graft. Using gamma camera images, an external graft platelet accumulation index (E-GPAI) was calculated as the In-111 activity in the graft area to the reference aorta at 24, 48, and 72 hours post implantation. Mean EGPAI ± SEM values for the ASA/DPM (n = 4) and control groups (n = 7) were 1.13 ± 0.16 and 1.34 ± 0.05 (NS) at 24 hours, 1.20 ± 0.16 and 1.33 ± 0.07 (NS) at 48 hours, and 1.38 ± 0.07 and 1.35 ± 0.10 (NS) at 72 hours, respectively. A similar internal graft platelet accumulation index (I-GPAI) was constructed based on In-111 activity in excised grafts and reference aorta measured in a scintillation counter. Mean I-GPAI ± SEM values for the PTFE ASA/DPM (n = 9) and control groups (n = 8) at 48 hours post implantation were 43.1 ± 2.7 and 216.8 ± 73.9 (P = 0.05), respectively. I-GPAI values for the SR grafts were 192.5 ± 43.1. Conclusion: The E-GPAI was not sensitive enough to demonstrate the effect of antiplatelet medication on platelet accumulation on the PTFE grafts. Excision of the graft with a section of reference aorta for measurement of the I-GPAI, however, was a sensitive ethod for evaluating the effect of antiplatelet medication

Key Words:

• animal model
• indium-111
• platelets
• vascular prosthesis