Endothelial cell damage and thrombus formation following temporary arterial occlusion

Abstract

The effects of restored blood flow on endothelial damage 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 min. The clips were removed and blood flow resumed for periods of 30 min, 1 h, 2 h and 24 h. A 2nd group was pretreated i.v. with heparin (1400 U/kg) and a 3rd group was pretreated orally with aspirin (50 mg/kg). SEM 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 h of restored blood flow. Examination of arterial segments compressed by the clip revealed endothelial desquamation and thrombus formation within 30 min of resumption of flow. The maximum degree of thrombus formation occurred within 1-2 h of resumption of flow with a subsequent decrease in the extent of deposition of platelets, fibrin, erythrocytes and leukocytes within 24 h. No change was found in composition or quantity of thrombus formation after pretreatment with heparin although, in the latter specispecimens, fibrin deposition was considerably less. Pretreatment with aspirin resulted in marked reduction in overall thrombus formation at the site of the clip following temporary occlusion.