Background and Purpose—In acute stroke patients treated with intravenous tissue plasminogen activator (t-PA), early recanalization of occluded arteries can improve the clinical outcome. The magnetic susceptibility effect of deoxygenated hemoglobin in red thrombi can present as hypointense signals on T2*-weighted gradient echo imaging. We investigated whether the gradient echo imaging M1 susceptibility vessel sign (M1 SVS) can predict no early recanalization after t-PA infusion.

Methods—Patients with internal carotid artery and M1 occlusion were prospectively studied. MRI studies, including DWI, T2*, and MRA, were performed before and within 30 minutes and 24 hours after t-PA infusion. The NIHSS score was obtained before and 7 days after t-PA administration. The relationship between the presence of the M1 SVS and no early recanalization and patient outcome was examined.

Results—A total of 48 patients (29 men; mean age, 74.6±11.2 years) were enrolled. M1 SVS was present in 13 (27.1%) patients and absent in 35 (72.9%) patients. There were no significant differences in clinical characteristics between the 2 groups. Follow-up MRA within 30 minutes after t-PA infusion revealed that 20 (57.1%) of the 35 patients without the M1 SVS had early recanalization, but that none of the 13 patients with the M1 SVS had early recanalization (P=0.0002). Seven days after t-PA infusion, dramatic improvement was more frequently observed in patients without the M1 SVS (51.4%) than in those with the M1 SVS (0%, P=0.0007).

Conclusion—The M1 SVS on T2* appears to be a strong predictor for no early recanalization after t-PA therapy.