LYSIS RATES WITH RT-PB VARY BETWEEN DIFFERENT HUMAN EMBOLI IN A RAT MODEL OF CEREBRAL EMBOLISM

In apparently similar conditions lysis rates of cerebral emboli treate d with thrombolytic drugs are quite variable. We used this model of ra t embolism with human emboli to investigate whether this was, at least partially, dependent on the characteristics of the embolus. Sixty-two male Wistar rats were embolized via the external carotid artery. Embo li obtained from peripheral vessel embolectomies of two different pati ents were trimmed to a standardized length and diameter. Subgroups of the 9 animals in the two emboli groups (labeled groups 1 and 2) were r andomly assigned to i.v. treatment with either saline, 1 mg/kg rt-PA o r 10 mg/kg rt-PA. Only cases with internal carotid artery occlusion we re included. Histology of both emboli was assessed by hematoxylin and eosin and trichromic Masson stainings. Recanalization rate was assesse d by means of sequential angiograms, classified by TIMI grades, perfor med from 30 to 120 min after embolization. Complete recanalization rat e in treated animals 2 h post-embolization was 88% for group 1 and 44% for group 2 (P < 0.05 chi-square test). The difference was based on t he higher rate of recanalization in cases treated with 1 mg/kg rt-PA: 8/9 cases in group 1 and 2/9 cases in group 2. Both emboli had a simil ar structure of fibrin with blood cells, Different human emboli of sim ilar size and apparently similar structure can show an unequal respons e to thrombolytic therapy. This finding could explain some of the vari ation in recanalization rates in cerebral embolism.