Abstract 3491: Transient Early Impairment of Dynamic Cerebral Autoregulation after Large-vessel Ischemic Stroke

Abstract

Background: Dynamic cerebral autoregulation (DCA) is the continuous early counterregulation of cerebral blood vessels to changes systemic blood pressure. DCA can become impaired after acute stroke, but it remains unclear to what extent autoregulation is affected and how that impairment progresses over time. Methods: A total of 22 patients admitted to Columbia University Medical Center with an acute, large-vessel ischemic stroke in the middle cerebral artery territory were included in the study. The mean NIHSS on admission was 10.2+/-6.5 (mean age 61+/-19.3 years, 68% women). DCA was assessed from simultaneous measurement of spontaneous blood pressure fluctuations and blood flow velocities using transcranial Doppler combined with finger plethysmography or invasive arterial catheter. Transfer function analysis was applied to calculate average phase shift in the very-low (0.02-0.07 Hz) and low (0.07-0.2 Hz) frequency range as a measure of impairment of cerebral autoregulation. Less shift indicated poorer regulation. The affected side was compared with the unaffected side. Patients underwent a total of three 10-minute recordings on days 0-2, 3-7 and >7. Univariate comparisons of data were performed using t-tests at single time points, and using generalized estimating equations with an exchangeable correlation matrix process to examine the change in phase shift between affected and unaffected hemispheres (delta) over time. Results: The first recording was performed an average 1.2+/-0.7 days after the ictus. In the very low frequency range, the average phase shift in the affected hemisphere was 43.7+/-42.3 degrees vs. 70.1+/-26.9 degrees in the unaffected hemisphere; p=0.02. In the low frequency range, the difference was 48.6+/-40.7 vs. 58.8+/-41.4 degrees; p=0.28. At the second measurement, which was done 4.2 +/-1.6 days after the ictus, there was a significant difference between the affected and unaffected hemisphere in the very low and low frequency (37.5+/-30.3 vs. 60.7+/-24.1 degrees, p=0.04 and 46.9+/-29.6 vs. 65.6+/-25.9 degrees, p=0.05, respectively). The third measurement was performed 10.1+/-2.2 days after the ictus. At that time there was no difference found between the affected and unaffected hemisphere in either frequency band (40.5+/-39.4 versus 41.3+38.4 degrees, p=0.92 and 46.1+/-34.6 vs. 34.6+/-36.7 degrees, p=0.22). Using the first recording as the reference, the delta phase shift in the low frequency range decreased minimally -- by -1.65 (CI: -17.5, 14.2) degrees -- on recording two (p=0.84), and significantly -- by -26.45 (CI: -50.7, -2.2) degrees -- on recording three (p=0.03). Discussion: These data suggest that cerebral autoregulation is impaired in the affected hemisphere in the first week after large-vessel ischemic stroke, and then normalizes by week two. These findings may have important implications for acute blood pressure management after stroke.