Speed of tPA-Induced Clot Lysis Predicts DWI Lesion Evolution in Acute Stroke

Abstract

Background and Purpose— We sought to evaluate the impact of the speed of recanalization on the evolution of diffusion- weighted imaging (DWI) lesions and outcome in stroke patients treated with tissue-type plasminogen activator (tPA). Methods— We evaluated 113 consecutive stroke patients with a middle cerebral artery occlusion who were treated with intravenous tPA. All patients underwent multiparametric magnetic resonance imaging studies, including DWI and perfusion-weighted imaging before and 36 to 48 hours after administration of a tPA bolus. Patients were continuously monitored with transcranial Doppler during the first 2 hours after tPA administration. The pattern of recanalization on transcranial Doppler was defined as sudden (<1 minute), stepwise (1 to 29 minutes), or slow (>30 minutes). Results— During transcranial Doppler monitoring, 13 (12.3%) patients recanalized suddenly, 32 (30.2%) recanalized in a stepwise manner, and 18 (17%) recanalized slowly. Baseline clinical and imaging parameters were similar among recanalization subgroups. At 36 to 48 hours, DWI lesion growth was significantly ( P =0.001) smaller after sudden (3.23±10.5 cm 3 ) compared with stepwise (24.9±37 cm 3 ), slow (46.3±38 cm 3 ), and no (51.7±34 cm 3 ) recanalization. The slow pattern was associated with greater DWI growth ( P =0.003), lesser degree of clinical improvement ( P =0.021), worse 3-month outcome ( P =0.032), and higher mortality ( P =0.003). Conclusions— The speed of tPA-induced clot lysis predicts DWI lesion evolution and clinical outcome. Unlike sudden and stepwise patterns, slow recanalization is associated with greater DWI lesion growth and poorer short- and long-term outcomes.