Influence of pretreatment MRI parameters on clinical outcome, recanalization and infarct size in 49 stroke patients treated by intravenous tissue plasminogen activator

We hypothesized that pretreatment magnetic resonance imaging (MRI) parameters might predict clinical outcome, recanalization and final infarct size in acute ischemic stroke patients treated by intravenous recombinant tissue plasminogen activator (rt-PA). MRI was performed prior to thrombolysis and at day 1 with the following sequences: magnetic resonance angiography (MRA), T2*-gradient echo (GE) imaging, diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). Final infarct size was assessed at day 60 by T2-weighted imaging (T2-WI). The National Institutes of Health Stroke Scale (NIHSS) score was assessed prior to rt-PA therapy and the modified Rankin Scale (m-RS) score was assessed at day 60. A poor outcome was defined as a day 60 m-RS score >2. Univariate and multivariate logistic regression analyses were used to identify the predictors of clinical outcome, recanalization and infarct size. Forty-nine patients fulfilled the inclusion criteria. Baseline NIHSS score was the best independent indicator of clinical outcome (p=0.002). A worse clinical outcome was observed in patients with tandem internal carotid artery (ICA)+middle cerebral artery (MCA) occlusion versus other sites of arterial occlusion (p=0.009), and in patients with larger pretreatment PWI (p=0.001) and DWI (p=0.01) lesion volumes. Two factors predict a low rate of recanalization: a proximal site of arterial occlusion (p=0.02) and a delayed time to peak (TTP) on pretreatment PWI (p=0.05). The final infarct size was correlated with pretreatment DWI lesion volume (p=0.025). Recanalization was associated with a lower final infarct size (p=0.003). In conclusion, a severe baseline NIHSS score, a critical level of pretreatment DWI/PWI parameters and a proximal site of occlusion are predictive of a worse outcome after IV rt-PA for acute ischemic stroke.