Hemorrhagic complications of thrombolytic therapy in experimental stroke.

Recent success with thrombolytic therapy for acute myocardial infarction has stimulated interest in its use for stroke. To determine the hemorrhagic potential of thrombolytic therapy in experimental cerebral infarction, we compared a group of tissue plasminogen activator-treated rabbits (n = 4) with 2 groups of streptokinase-treated rabbits (n = 6 in each), as well as with 3 groups of heparin-treated rabbits (n = 5 in each) and untreated controls (n = 12). Focal cerebral infarction was produced in rabbits by occlusion of the right common carotid and middle cerebral arteries coupled with 2 hours of halothane-induced hypotension. Treatment with heparin or thrombolytic agents began 24 hours after occlusion. One additional group was treated with streptokinase 1 hour after occlusion (n = 6) to determine the hemorrhagic potential of thrombolytic agents in evolving infarction. Rabbits were killed 29-33 hours after occlusion, and brain sections were examined using light microscopy. The results demonstrate that microscopic hemorrhage is frequently present in infarcted tissue irrespective of treatment. Gross cerebral hemorrhage did not occur in untreated rabbits or in rabbits treated with streptokinase 1 hour after occlusion. Only rabbits treated with streptokinase, tissue plasminogen activator, or excessive doses of heparin 24 hours after occlusion, at a time when cerebral infarction was well established, exhibited gross hemorrhage in the area of infarction. These data suggest that treatment of ischemic stroke with thrombolytic agents carries an increased risk of cerebral hemorrhage unless the agents are given early after the onset of symptoms.