Endothelial cell damage and thrombus formation following temporary arterial occlusion

Abstract

✓ The effects of restoration of blood flow on endothelial damage that occurs distal to the site of temporary arterial occlusion with surgical clips, and the effects of heparin and aspirin on thrombus formation at the site of the clip, were studied by scanning electron microscopy (SEM). The right carotid artery of 45 rabbits was occluded with a Heifetz clip for 30 minutes. The clips were then removed and blood flow resumed for periods of 30 minutes, 1 hour, 2 hours, and 24 hours. A second group was preteated intravenously with heparin (1400 units/kg), and a third group was pretreated orally with aspirin (50 mg/kg). The SEM analysis of arterial segments distal and proximal to the clip indicated that the frequency of occurrence of endothelial crater- and balloon-like vesicular defects decreased to zero within 24 hours of restoration of blood flow. Examination of arterial segments compressed by the clip revealed endothelial desquamation and thrombus formation within 30 minutes of resumption of flow. The maximum degree of thrombus formation occurred within 1 to 2 hours of resumption of flow, with a subsequent decrease in the extent of deposition of platelets, fibrin, erythrocytes, and leukocytes within 24 hours. No change was found in composition or quantity of thrombus formation after pretreatment with heparin although, in the latter specimens, fibrin deposition appeared considerably less. However, pretreatment with aspirin resulted in marked reduction in the overall quantity of thrombus formation at the site of the clip following temporary occlusion.