Residual vessel length on magnetic resonance angiography identifies poor responders to alteplase in acute middle cerebral artery occlusion patients: exploratory analysis of the Japan Alteplase Clinical Trial II.

BACKGROUND AND PURPOSE It remains unknown whether the effects of 0.6 mg/kg alteplase differ with occlusion site of the middle cerebral artery (MCA). We therefore evaluated the effects of 0.6 mg/kg intravenous alteplase in patients with different sites of MCA occlusion. METHODS An exploratory analysis was made of 57 patients enrolled in the Japan Alteplase Clinical Trial II (J-ACT II), originally designed to evaluate 0.6 mg/kg alteplase in Japanese patients with unilateral occlusion of the MCA (M1 or M2 portion). The residual vessel length (in mm), determined by pretreatment magnetic resonance angiography, was used to reflect the occluded site. The proportions of patients with valid recanalization (modified Mori grade 2 to 3) at 6 and 24 hours and a modified Rankin Scale (mRS) score of 0 to 1 and of 0 to 2 at 3 months were compared between the groups dichotomized according to length of the residual vessel. Multiple logistic-regression models were generated to elucidate the predictors of valid recanalization, mRS 0 to 1, and mRS 0 to 2. RESULTS Receiver operating characteristics analysis revealed that 5 mm was the practical cutoff length for dichotomization. In patients with an M1 length < 5 mm (n = 12), the frequencies of valid recanalization at 6 and 24 hours (16.7% and 25.0%) were significantly lower compared with those (62.1% and 82.8%, respectively) of the 45 patients with a residual M1 length ≥ 5 mm and an M2 occlusion (P = 0.008 for 6 hours, P < 0.001 for 24 hours). The proportions of patients who achieved an mRS of 0 to 1 and an mRS of 0 to 2 were also lower for those with an M1 length < 5 mm (8.3% and 16.7%, respectively) compared with the other group (57.8% and 68.9%, respectively; P = 0.003 for mRS 0 to 1, P = 0.002 for mRS 0 to 2). In logistic-regression models, the site of MCA occlusion (< 5 mm) was a significant predictor of valid recanalization at 6 and 24 hours and of an mRS of 0 to 1 and of mRS of 0 to 2. CONCLUSIONS In patients with acute MCA occlusion, a residual vessel length < 5 mm on magnetic resonance angiography can identify poor responders to 0.6 mg/kg alteplase. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00412867.