Simultaneous carotid ultrasound and transcranial Doppler to detect cholesterol crystal emboli from unstable carotid plaque to the brain

Detection of unstable carotid plaques at risk for cholesterol crystal (CC) emboli to the brain causing strokes can be challenging. Although plaques with lumen stenosis of >70 % have been shown to pose a risk for embolism, detection prior to this stage of plaque progression (<70 % stenosis) may identify early instability. One such approach would be to obtain simultaneous carotid ultrasound (CUS) and transcranial Doppler (TCD) that can detect CCs discharged from plaque as a signal of instability. Application of contact pressure as usually applied by the interrogating ultrasound probe over a carotid artery during CUS that can trigger high intensity transient signals (HITS) on TCD could provide insight into plaque instability. To test this hypothesis, we evaluated 23 patients with moderate stenosis (∼50 %) by CUS/TCD to check for instability. Of the patients insonated, 4/21 had evidence of HITS on TCD during CUS and 3 had neurological symptoms. The presence of HITS was observed only for emboli from heterogenous/complex plaques (4/14) 28.6 % (95 % CI: 0.084-0.581), <i>p</i> ≤ 0.05. Moreover, to confirm the role of CCs on HITS, we injected 1 or 5 CCs into the femoral circulation of a rabbit model and demonstrated that even a single crystal could be detected by a HIT on TCD. Detection of CCs by HITS with TCD was highly sensitive for number of injected crystals (1/1, 5/5) and specific (0/0 for whole blood) indicating 100 % accuracy. We propose that this simple and readily feasible approach could be useful to detect unstable carotid plaques at an early stage.