Does Body Weight Influence the Response to Intravenous Tissue Plasminogen Activator in Stroke Patients?

Background: The recommended dose of IV tissue plasminogen activator (t-PA) for ischemic stroke patients weighing > 100 kg (ISPW > 100 kg) is fixed at 90 mg. Elevated levels of plasminogen activator inhibitor-1 (PAI-1) and impaired fibrinolysis have been reported in heavy patients, suggesting that ISPW > 100 kg may require higher doses of t-PA. We hypothesized that ISPW > 100 kg are less likely to benefit from IV t-PA compared to patients who weigh <= 100 kg and receive a weight-based dose. Methods: We queried the National Institute of Neurological Disorders and Stroke t-PA study database, and performed multivariate logistic regression analyses to analyze the effects of weight (> 100 vs. <= 100 kg) and t-PA dose on functional outcomes at 3 months. Results: Six percent of the t-PA and 10% of the placebo cohorts had an actual body weight > 100 kg. Weight > 100 kg emerged as a predictor of worse outcome (OR = 5.76; p = 0.017) and neurological deterioration (OR = 3.4; p = 0.07) after t-PA. This negative impact of body weight on outcome was not seen among placebo-treated patients. We also found a trend for an association between lower doses of t-PA and unfavorable 3-month outcomes in t-PA-treated patients (OR = 1.9; p = 0.05). Conclusions: ISPW > 100 kg seem to derive less benefit from IV t-PA than their lighter counterparts. This may be partly attributed to the use of fixed non-weight-adjusted dosing in heavier patients. The mechanism(s) underlying this observation and its potential therapeutic implications require further investigations. Copyright (c) 2008 S. Karger AG, Basel