Intracranial collateralization determines hemodynamic forces for carotid plaque disruption
Brajesh K Lal1, Kirk W Beach, David S Sumner
1Center for Vascular Diagnostics, Department of Vascular Surgery, University of Maryland, Baltimore, MD 21201, USA. blal@smail.umaryland.edu
Journal of Vascular Surgery
|August 9, 2011
Summary
Incomplete circle of Willis collateralization increases disruptive forces on carotid plaques, making diameter reduction an inaccurate stroke risk predictor. Assessing flow rates and collateral circulation offers better risk assessment for carotid atherosclerosis.
Area of Science:
- Cardiovascular Science
- Neurology
- Biomedical Engineering
Background:
- Carotid atheroembolism risk assessment using percent diameter reduction is imperfect.
- Stroke from carotid stenosis often results from plaque disruption due to hemodynamic forces.
- The study investigates the impact of circle of Willis (COW) collateralization on these forces.
Purpose of the Study:
- To predict the effect of incomplete intracranial collateralization via the COW on disruptive hemodynamic forces acting on carotid plaques.
- To evaluate the accuracy of diameter reduction in assessing stroke risk.
- To explore alternative methods for refining stroke risk estimation.
Main Methods:
- A circuit model simulating intra- and extracranial arterial pathways and COW collaterals was developed.
- Pressure-flow relationships were modeled using fluid mechanics principles.
- Pressure drops across carotid stenosis were computed for scenarios with and without COW collateralization.
Main Results:
- Higher flow rates and velocities across carotid plaques were observed with a disconnected COW compared to an intact COW.
- Pressure drops across similar stenoses were significantly higher with a disconnected COW.
- Despite stenosis, mean brain blood flow was sustained, but achieved differently based on COW status.
Conclusions:
- Incomplete COW collateralization leads to increased shear stress on carotid plaques, elevating stroke risk.
- Percent diameter reduction is an inaccurate measure of atheroembolic stroke risk.
- Assessing carotid flow rates, velocities, and COW collateral status can improve stroke risk prediction in asymptomatic carotid atherosclerosis.
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