Low- Versus Standard-Dose Alteplase in Patients on Prior Antiplatelet Therapy: The ENCHANTED Trial (Enhanced Control of Hypertension and Thrombolysis Stroke Study).

BACKGROUND AND PURPOSE: Many patients receiving thrombolysis for acute ischemic stroke are on prior antiplatelet therapy (APT), which may increase symptomatic intracerebral hemorrhage risk. In a prespecified subgroup analysis, we report comparative effects of different doses of intravenous alteplase according to prior APT use among participants of the international multicenter ENCHANTED study (Enhanced Control of Hypertension and Thrombolysis Stroke Study). METHODS: Among 3285 alteplase-treated patients (mean age, 66.6 years; 38% women) randomly assigned to low-dose (0.6 mg/kg) or standard-dose (0.9 mg/kg) intravenous alteplase within 4.5 hours of symptom onset, 752 (22.9%) reported prior APT use. Primary outcome at 90 days was the combined end point of death or disability (modified Rankin Scale [mRS] scores, 2-6). Other outcomes included mRS scores 3 to 6, ordinal mRS shift, and symptomatic intracerebral hemorrhage by various standard criteria. RESULTS: There were no significant differences in outcome between patients with and without prior APT after adjustment for baseline characteristics and management factors during the first week; defined by mRS scores 2 to 6 (adjusted odds ratio [OR], 1.01; 95% confidence interval [CI], 0.81-1.26; P=0.953), 3 to 6 (OR, 0.95; 95% CI, 0.75-1.20; P=0.662), or ordinal mRS shift (OR, 1.03; 95% CI, 0.87-1.21; P=0.770). Alteplase-treated patients on prior APT had higher symptomatic intracerebral hemorrhage (OR, 1.82; 95% CI, 1.00-3.30; P=0.051) according to the safe implementation of thrombolysis in stroke-monitoring study definition. Although not significant (P-trend, 0.053), low-dose alteplase tended to have better outcomes than standard-dose alteplase in those on prior APT compared with those not using APT (mRS scores of 2-6; OR, 0.84; 95% CI, 0.62-1.12 versus OR, 1.16; 95% CI, 0.99-1.36). CONCLUSIONS: Low-dose alteplase may improve outcomes in thrombolysis-treated acute ischemic stroke patients on prior APT, but this requires further evaluation in a randomized controlled trial. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01422616.

Ischemic thresholds for gray and white matter: a diffusion and perfusion magnetic resonance study.

BACKGROUND AND PURPOSE: Although gray matter (GM) and white matter (WM) have differing neurochemical responses to ischemia in animal models, it is unclear whether this translates into differing thresholds for infarction. We studied this issue in ischemic stroke patients using magnetic resonance (MR) techniques. METHODS: MR studies were performed in patients with acute hemispheric ischemic stroke occurring within 24 hours and at 3 months. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) were calculated. After segmentation based on a probabilistic map of GM and WM, tissue-specific diffusion and perfusion thresholds for infarction were established. RESULTS: Twenty-one patients were studied. Infarction thresholds for CBF were significantly higher in GM (median 34.6 mL/100 g per minute, interquartile range 26.0 to 38.8) than in WM (20.8 mL/100 g per minute; interquartile range 18.0 to 25.9; P<0.0001). Thresholds were also significantly higher in GM than WM for CBV (GM: 1.67 mL/100 g; interquartile range 1.39 to 2.17; WM: 1.19 mL/100 g; interquartile range 0.94 to 1.53; P<0.0001), ADC (GM: 918x10(-6) mm2/s; 868 to 975x10(-6); WM: 805x10(-6); 747 to 870x10(-6); P<0.001), and there was a trend toward a shorter MTT in GM (GM 4.94 s, 4.44 to 5.38; WM 5.15, 4.11 to 5.68; P=0.11). CONCLUSIONS: GM has a higher infarction threshold for CBF, CBV, and ADC than WM in patients within 24 hours of ischemic stroke onset. Hence, when assessing patients for potential therapies, tissue-specific rather than whole-brain thresholds may be a more precise measure of predicting the likelihood of infarction.