Abstract T P181: Static And Dynamic Cerebral Autoregulation Dissociate In Asymptomatic Carotid Artery Disease
Background: High grade internal carotid artery (ICA) disease can alter cerebral autoregulation and thus increase risk for ischemia. We aimed to differentiate two types of autoregulation - dynamic cerebral autoregulation (DCA), thought to be a homeostatic process, and vasomotor reactivity (VMR), which determines cerebrovascular reserve - in patients with asymptomatic ICA stenosis.
Methods: Twenty-two patients (age 50-93, 16M) with unilateral 80-100% ICA occlusion but no stroke underwent quantitative CBF measurements using continuous arterial spin labeling (CASL) MRI. DCA was performed by continuous insonation of both middle cerebral arteries with transcranial Doppler for 10 minutes at depth 56mm using a standard head frame. Phase shift (PS) between spontaneous oscillations in blood pressure (measured with finger photoplethysmography (Finapres)) and MCA mean flow velocities (MFV) at frequencies .06-.12 Hz was calculated for each hemisphere using transfer function analysis. Lower degree of PS indicated worse autoregulation (abnormal <24deg1). VMR was determined as a response to 2 minutes of 5% CO2 inhalation (abnormal <2% rise in MCA MFV per mmHg PCO2 by Doppler-integrated inline capnometer (Spencer Technologies)). T-test Chi-square, and multivariable linear regression were used to look for associations between VMR, DCA, and hemispheral CBF (SPSS v.22).
Results: MCA MFV (p<.001), VMR (p=.002), and CBF (p<.003), were lower in the ICA occlusion hemisphere. DCA difference approached significance (p=0.064). Controlling for age and anterior circle of Willis collateral cross-filling, DCA (p=0.024), but not VMR (p=0.079) on the occluded side was associated with greater hemispheral CBF asymmetry (F=6.87, p=0.024). VMR and DCA were not correlated (Fisher exact =.61).
Conclusions: DCA but not VMR correlated with a low flow state produced by high grade ICA disease in asymptomatic patients. Our results suggest that in ICA stenosis dynamic/homeostatic mechanisms may be affected without substantially altering the static/protective mechanism of cerebrovascular reserve. Ongoing studies will investigate the effect of these two autoregulatory mechanisms on vascular cognitive impairment.
1 Ortega-Gutierrez S, et al. J Neuroimaging. 2014 24:379-86
Author Disclosures: R.S. Marshall: Research Grant; Significant; NINDS 1R01NS076277. R.M. Lazar: Research Grant; Significant; NINDS 1R01NS076277. M.A. Pavol: Research Grant; Significant; NINDS 1R01NS076277. S. Dharssi: Research Grant; Modest; NINDS 1R01NS076277. Y. Qiu: Research Grant; Modest; NINDS 1R01NS076277. K. Slane: Research Grant; Modest; NINDS 1R01NS076277. I. Asllani: Research Grant; Significant; NINDS 1R01NS076277.
- © 2015 by American Heart Association, Inc.