Abstract W P170: Hemodynamic Effects in Carotid Occlusion Using Arterial Spin Labeling and Transcranial Doppler
Background: High grade carotid stenosis produces hemodynamic effects on the brain, but the relationship between cerebral autoregulation, absolute CBF and neurovascular coupling has not been well-delineated.
Methods: Twelve subjects (age 74±9, 3F) with unilateral ICA stenosis (80-100% occluded) but no infarct (asymptomatic or TIA only) underwent dynamic cerebral autoregulation (DCA) testing with transcranial Doppler by comparing phase shift (PS) of spontaneous oscillations in blood pressure (measured with finger photoplethysmography (Finapres)) versus MCA flow velocities at frequencies .06-.12 Hz using transfer function analysis, lower degree of PS indicating worse autoregulation.Neurovascular coupling was assessed by amplitude of absolute increase in CBF in bilateral Brodman area (BA) 4 during a bilateral repetitive hand closure task using continuous arterial spin labeling (CASL) MRI. Four activation (ON) periods were averaged and subtracted from 4 rest (OFF) periods. Resting CBF for each hemisphere’s motor cortex was determined by averaging the OFF periods.
Results: All subjects showed: 1) hemispheric asymmetry in baseline CBF with the occluded side being on average 25mL/100g*min (+/- 14 mL/100g*min) lower than the unoccluded hemisphere. 2) hemispheric asymmetry in motor activation: unoccluded hemisphere average activation (mean_CBF_ON - mean_CBF_OFF) in BA4 was 23.7mL/100g*min, representing a 21% increase in local CBF due to activation; occluded hemisphere mean activation was 14 mL/100g*min, representing 18% percent increase in local CBF. 3) Hemispheric asymmetry in DCA, PS=33.1 deg ± 31 on the occluded side vs. 43.5 deg±23 on the non-occluded side. Both the hemispheral difference in baseline CBF (impaired flow) and the difference in DCA measurement (impaired autoregulation) were good predictors of the lower activation (neurovascular coupling) on the occluded hemisphere: R2 = 0.85 and 0.80, respectively.
Conclusion: Both impaired resting CBF and impaired cerebral autoregulation appear to contribute to decreased neurovascular coupling in carotid artery occlusive disease, representing a potential mechanism for occult neuronal dysfunction such as mild cognitive impairment in this patient population.
Author Disclosures: R.S. Marshall: Research Grant; Significant; NINDS 1R01NS076277-01A1. R.M. Lazar: Research Grant; Significant; NINDS 1R01NS076277-01A1. M.A. Pavol: Research Grant; Modest; NINDS 1R01NS076277-01A1. S. Dharssi: Research Grant; Modest; NINDS 1R01NS076277-01A1. K. Slane: Research Grant; Significant; NINDS 1R01NS076277-01A1. I. Asllani: Research Grant; Significant; NINDS 1R01NS076277-01A1.
- © 2014 by American Heart Association, Inc.