New method of embolus preparation for standardized embolic stroke in rabbits.

BACKGROUND AND PURPOSE Although thromboembolic stroke is caused by red, white, or mixed clots, the emboli previously used in animal studies on thrombolysis were more often red than white. Because this might be one of the reasons why thrombolysis is less effective in patients than in experimental stroke, we developed a new method of preparing highly standardized red and fibrin-rich white emboli. METHODS The middle cerebral artery of 20 rabbits was embolized with either red or fibrin-rich white autologous emboli. Cerebral perfusion was monitored by MRI. RESULTS Red emboli consisted of closely packed erythrocytes within a sparse fibrin net and white emboli of a dense mass of fibrin with only few other blood cells. Infarct volumes were 26+/-4% (mean+/-SD) of the ischemic hemisphere with red and 27+/-6% with white emboli. The relative regional cerebral blood volume dropped below 50% 90 minutes after vascular occlusion with either type of embolus. Late spontaneous lysis and hemorrhagic complications occurred in 37.5% of red but not in white embolus cases. CONCLUSIONS Emboli prepared by our technique result in standardized cerebral infarctions. Size and composition of the emboli continuously can be adjusted according to the experimental requirements.