Platelet Inhibitory Drugs: An In Vivo Method of Evaluation in Patients

Summary

The measurement of platelet deposition in human thrombi is essential for the evaluation of platelet-inhibitory drugs and prosthetic materials for use in patients. The rate of ¹¹¹Indiumlabelled platelet accumulation on Dacron arterial grafts was measured in 27 patients randomised to take either aspirin and dipyridamole (ASA + DPM) or placebo. Autologous platelets were labelled and re-injected seven days following surgery and the graft thrombogenidty index calculated as the daily rise in the ratio of emissions from the graft over a reference site.

The mean (± SD) thrombogenidty index in 12 patients undergoing femoro-popliteal bypass was 0.25 ± 0.09 on placebo and 0.16 ± 0.07 on ASA + DPM started pre-operatively (p Ã0.05). Post-operative ASA + DPM therapy started two days following platelet labelling in 15 patients with aorto-femoral grafts also significantly reduce thrombogenidty to 0.12 ± 0.05 compared with 0.25 ± 0.08 on placebo (p Ã0.01). In the latter patients the ratio of emissions from the graft over reference fell significantly on starting ASA + DPM, suggesting a net loss of platelets from the graft. These results indicate that the rate of in vivo platelet accumulation on Dacron grafts can be quantitated and that ASA + DPM reduced this rate in man.

Keywords

Dacron arterial grafts - Thrombosis - Blood platelets - Platelet metabolism - Arterial occlusive disease - Antiplatelet drugs

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