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Influence of poststenotic collateral pressure on blood flow velocities within high-grade carotid artery stenosis:
H Zachrisson1, B Berthelsen, C Blomstrand
1Department of Clinical Physiology, Sahlgrenska University Hospital, Göteborg, Sweden. helene.zachrisson@sahlgreska.se
Insights
Blood flow velocity in internal carotid artery stenosis is influenced by collateral circulation. Lower stump pressure, indicating better collateral flow, correlates with lower velocities, impacting stenosis assessment.
Area of Science:
- Neurology
- Vascular Surgery
- Medical Imaging
Background:
- High-grade internal carotid artery stenosis can lead to reduced blood flow.
- Intracranial collateral vessels may influence pressure gradients and blood flow velocities across stenoses.
Purpose of the Study:
- To prospectively investigate the impact of intracranial collateral vessels on blood flow velocities within high-grade internal carotid artery stenoses.
- To assess the relationship between collateral circulation and hemodynamic parameters in carotid artery stenosis.
Main Methods:
- Investigated 45 patients with high-grade internal carotid artery stenoses preoperatively and during carotid endarterectomy.
- Utilized duplex ultrasound, transcranial Doppler, and angiography to assess stenosis and collateral flow.
- Measured systolic and diastolic blood pressures, including stump pressure, during intraoperative carotid artery cross-clamping.
Main Results:
- Found a significant inverse correlation between blood flow velocities and stump pressures in high-grade internal carotid artery stenoses.
- Patients with collateral flow to the anterior circle of Willis showed varying end-diastolic velocities.
- Lower stump pressures were observed in patients with higher end-diastolic velocities, despite similar angiographic stenosis grades.
Conclusions:
- Blood flow velocities within internal carotid artery stenoses are inversely dependent on poststenotic collateral perfusion pressure (stump pressure).
- Discrepancies between angiography and ultrasound findings in stenosis grading should consider collateral influences.
- Stump pressure is a critical factor in interpreting hemodynamic significance of internal carotid artery stenosis.
Purpose:
The driving force for blood flow through a high-grade stenosis in the internal carotid artery can be expressed as the pressure gradient over the stenosis itself, which, however, might be reduced by the back pressure exerted by distal collateral vessels. Theoretically the maximum blood flow velocity as a measure of the functional grade of obstruction may therefore be lower than what is expected from morphologic gradations of the stenosis. This study was designed to test prospectively the influence of intracranial collateral vessels on blood flow velocities within high-grade internal carotid artery stenoses.
Patients And Methods:
Forty-five consecutive patients (age 66 +/- 11) with high-grade internal carotid artery stenoses were investigated before and during carotid endarterectomy. The preoperative investigations included duplex ultrasound scanning of the neck vessels, transcranial Doppler scanning for assessment of collateral flow to the middle cerebral artery and angiography. Carotid endarterectomy was performed with patients under deep general anesthesia without a shunt. Systolic and diastolic internal carotid artery blood pressures were measured before and during intraoperative cross-clamping (ie, stump pressure) of the carotid arteries.
Results:
Within high-grade internal carotid artery stenoses, maximum systolic and end-diastolic blood flow velocities showed a significant inverse correlation to the corresponding systolic and diastolic stump blood internal carotid artery blood pressures. All patients with spontaneous collateral flow to the ipsilateral anterior part of the circle of Willis were divided into a group with relatively high and another one with low end-diastolic blood flow velocities. The stump pressure was significantly lower in patients with high end-diastolic blood flow velocities in spite of the fact that the mean angiographic grade of stenosis did not differ significantly between the groups.
Conclusions:
Flow velocities within a high-grade internal carotid artery stenosis are inversely dependent on the stump pressure, that is the poststenotic collateral perfusion pressure. This should be taken into consideration in case of discrepancies between angiography and ultrasound outcome.
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