Long-term mortality in patients with stroke of undetermined etiology

Background and Purpose-The determination of stroke etiology is essential for planning treatment for stroke prevention. However, the etiology of stroke is undetermined in many patients. Methods-During a 10-year period, consecutive patients with acute ischemic stroke were enrolled. The stroke etiology was determined based on the Trial of ORG 10172 in Acute Stroke Treatment classification. Long-term mortality and causes of death were identified using death certificates. The standardized mortality ratio was calculated to compare the mortality in patients with stroke and that in the general Korean population. Results-In total, 3278 patients were enrolled and followed-up for a median of 3.4 years (interquartile range, 1.5-5.7). The stroke subtype was undetermined in 37% because of negative evaluation (21.2%), multiple causes (10.6%), and incomplete evaluation (4.8%). Poor functional outcome at 3 months (modified Rankin scale score >2) was more frequent in patients with an incomplete evaluation than in those with the other stroke subtypes (49.6% vs 24.5%; P<0.001). During follow-up, 781 patients (23.8%) died. The overall cumulative death rate was highest in patients with an incomplete evaluation (12.7% within 30 days, 25.5% within 1 year, and 35.7% within 3 years), followed by those with cardioembolism. Multivariate analysis after adjusting for covariates including initial stroke severity, the mortality of patients with an incomplete evaluation was second lowest after cardioembolism, whereas that in patients with a negative evaluation was low. Conclusions-Long-term mortality in patients with an incomplete evaluation was quite high. Etiologic work-up helps to better define the stroke subtype and determine the prognosis.