Frequency and determinants of microembolic signals on transcranial Doppler in unselected patients with acute carotid territory ischemia - A prospective study

Background and Purpose: Few data exist regarding to the occurrence of microembolic high-intensity transient signals (HITS) on transcranial Doppler ultrasound (TCD) in unselected acute stroke patients. The aim of this study was to investigate prospectively the frequency and determinants of HITS in acute carotid territory ischemia. We hypothesized that carotid artery disease, cardiac abnormalities, and nonlacunar infarcts were independent predictors of HITS in acute stroke. Methods: We investigated 145 consecutive patients with acute internal carotid artery territory ischemia. The median time interval between stroke and TCD examination was 2 days. TCD monitoring was performed for 30 min on each middle cerebral artery. The frequency of HITS was cross-classified with carotid artery status, potential cardiac sources of embolism, and nonlacunar infarct subtype. Multivariate logistic regression models determined the independent relationship of these variables to HITS. Results: Microembolic signals were detected in 35 patients (24.1%), Ipsilateral carotid artery disease was significantly and independently associated with HITS (odds ratio 3.3, 95% confidence interval 1.4-7.8, p = 0.007), whereas potential cardiac sources (OR 1.07, 95% CI 0.48-2.4, p = 0.84) and infarct subtype (OR 0.84, 95% CI 0.29-2.4, p = 0.75) were not. Conclusions: High-intensity transient signals can be found in almost 25% of patients with acute anterior cerebral circulation ischemia and are significantly more prevalent among those with symptomatic carotid artery disease. Future clinical studies are required to determine whether HITS are a marker of increased stroke recurrence and can help to clarify stroke etiology in patients with competing stroke mechanisms.