Does Preexisting Antiplatelet Treatment Influence Postthrombolysis Intracranial Hemorrhage in Community-treated Ischemic Stroke Patients? An Observational Study

Objectives Intracranial hemorrhage (ICH) after acute stroke thrombolysis is associated with poor outcomes. Previous investigations of the relationship between preexisting antiplatelet use and the safety of intravenous (IV) thrombolysis have been limited by low event rates. The objective of this study was to determine whether preexisting antiplatelet therapy increased the risk of ICH following acute stroke thrombolysis. The primary hypothesis was that antiplatelet use would not be associated with radiographic evidence of ICH after controlling for relevant confounders. Methods Consecutive cases of thrombolysis patients treated in the emergency department (ED) were identified using multiple methods. Retrospective data were collected from four hospitals from 1996 to 2004 and 24 other hospitals from 2007 to 2010 as part of a cluster-randomized trial. The same chart abstraction tool was used during both time periods, and data were subjected to numerous quality control checks. Hemorrhages were classified using a prespecified methodology: ICH was defined as presence of hemorrhage in radiographic interpretations of follow-up imaging (primary outcome). Symptomatic ICH (sICH) was defined as radiographic ICH with associated clinical worsening. A multivariable logistic regression model was constructed to adjust for clinical factors previously identified to be related to postthrombolysis ICH. Sensitivity analyses were conducted where the unadjusted and adjusted results from this study were combined with those of previously published external studies on this topic via meta-analytic techniques. Results There were 830 patients included, with 47% having documented preexisting antiplatelet treatment. The mean (+/- standard deviation [SD]) age was 69(+/- 15)years, and the cohort was 53% male. The unadjusted proportion of patients with any ICH was 15.1% without antiplatelet use and 19.3% with antiplatelet use (absolute risk difference=4.2%, 95% confidence interval [CI]=1.2% to 9.6%); for sICH this was 6.1% without antiplatelet use and 9% with antiplatelet use (absolute risk difference=3.1%, 95% CI=1% to 6.7%). After adjusting for confounders, antiplatelet use was not significantly associated with radiographic ICH (odds ratio [OR]=1.1, 95% CI=0.8 to 1.7) or sICH (OR=1.3, 95% CI=0.7 to 2.2). In patients 81years and older, there was a higher risk of radiographic ICH (absolute risk difference=11.9%, 95% CI=0.1% to 23.6%). The meta-analyses combined the findings of this investigation with previous similar work and found increased unadjusted risks of radiographic ICH (absolute risk difference=4.9%, 95% CI=0.7% to 9%) and sICH (absolute risk difference=4%, 95% CI=2.3% to 5.6%). The meta-analytic adjusted OR of sICH for antiplatelet use was 1.6 (95% CI=1.1 to 2.4). Conclusions The authors did not find that preexisting antiplatelet use was associated with postthrombolysis ICH or sICH in this cohort of community treated patients. Preexisting tobacco use, younger age, and lower severity were associated with lower odds of sICH. The meta-analyses demonstrated small, but statistically significant increases in the absolute risk of radiographic ICH and sICH, along with increased odds of sICH in patients with preexisting antiplatelet use. ACADEMIC EMERGENCY MEDICINE 2013; 20:146-154 (C) 2013 by the Society for Academic Emergency Medicine