Early infarct growth predicts long-term clinical outcome after thrombolysis

Background: Ischemic lesion growth may be a surrogate marker of clinical outcome, but no such interrelationship after thrombolysis has yet been determined. We evaluated the association between early infarct growth on diffusion-weighted imaging (DWI) and long-term clinical outcome after thrombolysis. Methods: We retrospectively reviewed outcomes in patients with acute middle cerebral artery territory stroke who had been treated with intravenous tissue plasminogen activator or intra-arterial urokinase. DWI lesion volumes were measured at baseline and within 7 days, and the difference was calculated. Clinical outcome was evaluated using the modified Rankin Scale (mRS) at 3 months. Good and poor clinical outcomes were defined as: a) mRS 0-1 vs. mRS 2-6, b) mRS 0-2 vs. mRS 3-6, and c) responder analysis which was influenced by the baseline National Institutes of Health Stroke Scale (NIHSS) scores: good and poor outcomes were defined as mRS 0 vs. mRS 1-6 if the baseline NIHSS score was < 8, mRS 0-1 vs. mRS 2-6 if the NIHSS score was 8-14, and mRS 0-2 vs. mRS 3-6 if the NIHSS score was > 14. The relationship between the ischemic lesion volume change and clinical outcome was explored. The cut-off value of infarct growth predicting long-term outcome was estimated using receiver operating characteristic analysis. Results: Of the 81 patients included, 67 (82.7%) showed lesion growth, and absolute growth was significantly related to poor outcomes (P < 0.001 all for mRS 2-6, mRS 3-6, and responder analysis). Multivariate analysis showed that absolute lesion growth was an independent predictor of poor outcome, defined as mRS 2-6 (P = 0.002; odds ratio [OR], 1.06; 95% confidence interval [CI], 1.02-1.10), mRS 3-6 (P = 0.001; OR, 1.06; 95% CI, 1.02-1.10), and poor outcome by responder analysis (P = 0.001; OR, 1.06; 95% CI, 1.03-1.10). The cut-off values of lesion growth that discriminated between good and poor outcomes were 14.11 cm³ for mRS 2-6; 15.87 cm ³ for mRS 3-6; and 14.11 cm³ in responder analysis. Conclusions: Early DWI lesion growth is an independent predictor of poor outcome after thrombolysis and may serve a potential surrogate marker of clinical outcome in acute stroke trials.