Dynamic monitoring of platelet deposition on severely damaged vessel wall in flowing blood. Effects of different stenoses on thrombus growth.

The formation of an arterial thrombus is a dynamic process that depends upon the characteristics of blood flow, the triggering substrate, and the blood components. We have developed and characterized a sensitive and specific computer-assisted nuclear scintigraphic method to study the dynamics of platelet deposition on severely damaged vessels both in vitro and in vivo in nonstenotic and stenotic flow conditions. Heparinized pig blood with Indium-111-labeled platelets was perfused for 50 minutes. Method variability in both static and flowing conditions was evaluated by Indium-111-labeled transferrin and Indium-111-labeled platelets. Positive scintigrams were obtained mainly in the presence of severe high grade stenoses on a thrombogenic substrate. Since the method is highly sensitive, computer-assisted axial dependence analysis was performed on the scintigraphic images to locate the thrombotic accumulation with respect to the area of the stenosis and to monitor the dynamic changes in platelet accumulation over time. Both in vitro and in vivo the highest level of platelet deposition occurred at the apex of the 80% stenosis, where embolization could be usually detected after 30 minutes of perfusion. This study is the first to assess the dynamics of thrombus growth in nonparallel flow streamlines such as are encountered in stenotic vessels. This method provides a new experimental tool with which to study factors affecting thrombus formation and stability.