Cerebral dysautoregulation and the risk of ischemic events in occlusive carotid artery disease

Dynamic cerebral autoregulation assessed from blood pressure transients can be considerably impaired in severe internal carotid artery (ICA) obstruction. It is unknown whether impaired autoregulation indicates an increased risk of subsequent ischemic events in this situation. 165 patients with ICA stenosis (> 70%) or occlusion were prospectively followed until anterior circulation stroke, transient ischemic attack, carotid recanalization without prior event, death or study end. Transcranial Doppler sonography was used to determine autoregulation in both middle cerebral arteries from spontaneous blood pressure fluctuations (correlation coefficient indices Dx and Mx) and respiratory-induced 0.1 Hz oscillations (phase). Standard CO2 reactivity (CO2R) was additionally assessed. All indices were classified as impaired vs. preserved according to reference values from 79 age-matched controls. During median follow-up of 24.5 months, there were 16 ischemic events over ipsilateral sides. Competing risk: analysis revealed a significant predictive effect on ipsilateral ischemic events for impaired Dx (rate ratio 8.2 [95% confidence interval 1.7-39], p = 0.0079), phase (5.0 [2-13], p = 0.0007) and CO2R (9.4 [2.2-40], p = 0.0025). Restricting analysis to severe stenosis alone (n = 103), only impaired phase (rate ratio 8.6 [1.6-45], p = 0.01) remained as a significant predictor. In a continuous statistical model, only Dx and Mx were significant predictors of ischemic events (p = 0.012 and p = 0.016). In conclusion, impaired dynamic cerebral autoregulation indicates an increased risk of subsequent ischemic events in severe obstructive ICA disease. Its clinical application might thus be of help in identifying higher risk patients.