High Intensity Transient Signals and Carotid Artery Disease

To determine the clinical significance of high intensity transient signals (HITS) in patients with internal carotid artery stenoses (≥ 60%), we examined the occurrence of these signals in 18 asymptomatics and 36 symptomatic carotid artery lesions and recent (< 72 h) symptoms. HITS were significantly more frequent in symptomatic (7/36) than in asymptomatic (0/18) carotid disease (p < 0.001). HITS tended to be associated with heterogeneous echogenicities and surface irregularities of plaques as evidenced by color-coded duplex sonography; in addition, HITS occurred significantly less often during effective anticoagulation (14% during heparin treatment vs. 36% in controls, p < 0.05). These findings suggest that HITS associated with carotid artery stenosis may reflect clinically silent artery-to-artery microembolism. However, since only the minority of patients with a recent history of cerebral ischemia presented with HITS, their predictive value with regard to recent symptoms is poor, and the question whether these patients are at higher risk of secondary events remains unsettled.