Radiolabelled Platelets in Cardiovascular Diseases

The recognition of the various factors controlling platelets vessel wall interaction in normal hemostasis and the role of platelets, clotting factors, and prostaglandins, in thromboembolic disease, atherosclerosis and post-prostheses implantation have stimulated interest in the evaluation of in vivo thrombus formation, embolization, and the evaluation of various prophylactic and therapeutic interventions. In vitro studies of platelets adhesion to deendothelialized vessel or biomaterials (catheters, synthetic vascular grafts, arterio-venous shunts, conduits, mechanical valves, ventricular assist devices and artificial heart) involve the use of light or electron microscopy and/or 51-Cr or III-In-platelets and Iodine-labelled clotting factors, mainly fibrinogen (1–6). In vivo consumption of platelets has been measured with several tracers including 51-Cr and III-In-labelled platelets (7–9) . Chromium-51 appears to be a marker of platelet activation and Ill-Indium appears to be a marker of platelet consumption. Although platelets had been labelled with Technetium-9 9m, the radionuclide washes off from the platelets with time after administration. Recently, lipid soluble 99m-Tc-complex (99m-Tc-hexamethylene propyleneamine oxine) had been used for granulocyte and platelet labelling. This tracer may be useful for repeated measurements of platelets thrombosis and surface passivation.