Prevalence of Microembolic Signals in Embolic Stroke of Undetermined Source and Other Subtypes of Ischemic Stroke.

Background and Purpose- Embolic stroke of undetermined source (ESUS) has been proposed to cause thromboembolic infarction from unknown but potential embolic sources. However, an embolus remains undetected in ESUS. The goal of this study was to characterize the prevalence and risk factors of microembolic signals (MESs) in ESUS. Methods- We examined 108 patients with acute ischemic stroke in the internal carotid artery territory or transient ischemic attack within 14 days of symptom onset and who were admitted to our hospital between April 2017 and March 2019. MESs were monitored in the middle cerebral artery on transcranial Doppler for 60 minutes. We examined the prevalence and number of MES in ESUS and other stroke subtypes, such as cardioembolism, large artery atherosclerosis, cerebral small vessel disease, and transient ischemic attack. The present study was registered in University Hospital Medical Information Network Clinical Trials Registry (UMIN000031913). Results- MESs were detected in 33 (31%) of 108 patients. ESUS showed the highest proportion (12/24 [50%]), followed by large artery atherosclerosis (8/20 [40%]), cardioembolism (6/18 [33%]), transient ischemic attack (4/24 [17%]), and cerebral small vessel disease (3/21 [14%]). Univariate analysis showed that higher systolic blood pressure, body mass index, hemoglobin A1c, and ESUS were significantly associated with MES. In multiple logistic regression analysis, ESUS remained significantly associated with MES after adjustment for described covariates from univariate analysis (odds ratio, 2.86 [95% CI, 1.01-8.08]). Conclusions- This study demonstrated significant association of ESUS with MES, supporting the embolic nature of this stroke subtype. Registration- URL: https://upload.umin.ac.jp. Unique identifier: UMIN000031913.