Effect of heparin reversal following endarterectomy in an atherosclerotic animal model.

A focal atherosclerotic plaque was induced in the aortas of New Zealand White female rabbits by a balloon injury and an atherogenic diet. Under general anesthesia and systemic heparinization, endarterectomy was performed using the operating microscope. Animals were sacrificed at 5, 10, 20, and 60 min following the endarterectomy and operated aortic segments were perfused and examined using scanning electron microscopy. Each segment was compared to a similar segment of endarterectomized aorta from a normal, nonatherosclerotic rabbit. Thrombus formation including aggregated platelets, red cells, and fibrin was found to be more pronounced in the atherosclerotic segments. Ten more atherosclerotic rabbits underwent identical procedures except that heparin was reversed using protamine sulfate 5 min following the endarterectomy. When these specimens were compared to a similar atherosclerotic group without heparin reversal, it was evident that a tremendous thrombogenic process had taken place in the "reversed" segments. This study suggests that atherosclerosis may alter thrombogenesis following an operative vascular procedure and that early reversal of heparin following an endarterectomy should be viewed with caution.