Predicting ischaemic stroke subtype from presenting systolic blood pressure: the BASIC Project.

OBJECTIVE We hypothesized that low presenting systolic blood pressure (SBP) predicted cardioembolic stroke aetiology. DESIGN Active and passive surveillance were used to identify all ischaemic strokes as part of the Brain Attack Surveillance in Corpus Christi (BASIC) population-based study. Multinomial logistic regression was used to examine the association between stroke subtype and first documented SBP in the medical record. SETTING Nueces County, TX, USA (313,645 residents in 2000). The community is urban with the majority of the population residing in the city of Corpus Christi. The area is served by seven adult acute care hospitals. PATIENTS Three hundred and eight cases with completed ischaemic stroke and determined subtype aetiology between January 2000 and December 2002. RESULTS Lower presenting SBP was associated with stroke subtype (P = 0.001). This association remained significant in the final model adjusted for age and history of coronary artery disease. The odds of cardioembolic versus small vessel occlusion increased by 20% (OR = 1.20, 95% CI: 1.07-1.35) for every 10 mmHg decrease in presenting SBP. Other covariates including race/ethnicity, gender, history of hypertension, and diabetes were neither significant predictors of stroke subtype, nor did they confound the association of SBP and stroke subtype. A 5 year increase in age increased the odds of cardioembolic subtype by 25% (OR = 1.25, 95% CI: 1.07-1.47). CONCLUSIONS Lower initial SBP and older age at ischaemic stroke presentation were associated with cardioembolic stroke. Suspicion of cardioembolic stroke should be increased in those presenting with low SBP.