Differential pattern of tissue plasminogen activator-induced proximal middle cerebral artery recanalization among stroke subtypes

Background and Purpose - We aimed to evaluate the timing, speed, and degree of tissue plasminogen activator (tPA)-induced recanalization in patients with proximal middle cerebral artery (MCA) occlusion of different stroke subtypes. Methods - We evaluated 72 patients with acute stroke caused by proximal MCA occlusion treated with intravenous tPA in <3 hours. Transcranial Doppler monitoring of recanalization was conducted during tPA infusion and at 6 hours. Strokes were categorized as large-vessel disease strokes, cardioembolic strokes, or strokes of undetermined origin according to Trial of Org 10172 in Acute Stroke Treatment criteria. Results - During 1-hour tPA infusion, recanalization occurred in 34 patients (47%); 32% showed a sudden, 50% showed a stepwise, and 18% showed a slow pattern of recanalization. One-hour recanalization was more frequent in patients with cardioembolic stroke (59%) compared with large-vessel disease (8%) and undetermined origin (50%) strokes. A cardiac source of emboli was identified in 81% of patients who showed a sudden clot breakup during tPA infusion. Rate of complete recanalization at 6 hours was higher (P=0.006) in patients with cardioembolic stroke (50%) compared with other stroke subtypes (27%). Sudden recanalization was associated (P=0.002) with a higher degree of neurological improvement at 24 hours compared with stepwise, slow, and no recanalization. A graded response in long-term outcome was observed in relation to the speed of clot lysis during tPA administration. Conclusions - We demonstrate that the pattern of tPA-induced MCA recanalization differs among stroke subtypes. Early recanalization was more frequent, faster, and more complete in patients with cardioembolic stroke compared with other stroke subtypes.