Bilateral severe carotid artery stenosis or occlusion - cerebral autoregulation dynamics and collateral flow patterns
1Department of Neurology and Clinical Neurophysiology, University of Freiburg, Freiburg, Germany.
Insights
Dynamic cerebral autoregulation (DCA) is severely impaired in critical bilateral carotid stenosis. Collateral flow patterns significantly impact hemodynamic status, with secondary collaterals indicating poorer outcomes.
Area of Science:
- Neurology
- Vascular Medicine
- Cerebrovascular Physiology
Background:
- Bilateral severe internal carotid artery obstruction presents a hemodynamically critical state.
- Understanding dynamic cerebral autoregulation (DCA) and collateral flow is crucial in these patients.
Purpose of the Study:
- To analyze dynamic cerebral autoregulation (DCA) in patients with bilateral severe carotid stenosis or occlusion.
- To correlate DCA parameters with various collateral flow patterns.
Main Methods:
- Noninvasive assessment of DCA using transfer function analysis (phase shift) of arterial blood pressure and cerebral blood flow velocity.
- Measurement of CO2-reactivity via 7% CO2 inhalation.
- Comparison between 30 patients with bilateral stenosis and 30 controls with unilateral stenosis.
Main Results:
- A pronounced reduction in phase shift was observed in bilateral critical stenosis (90-100%).
- Collateral patterns significantly influenced DCA; 'Willisian' collaterals were associated with better phase shift, while secondary collaterals indicated poorer hemodynamic status.
- Symptomatic patients exhibited significantly lower phase shift and CO2-reactivity values.
Conclusions:
- DCA is severely impaired in critical bilateral carotid stenosis or occlusion.
- Insufficient collateral supply, particularly sole reliance on secondary collaterals or functionally stenosed primary collaterals, signifies a poor hemodynamic status.
- Transfer function phase analysis offers a physiologically supported method for assessing cerebral hemodynamic compromise.
Background:
Bilateral severe obstruction of the internal carotid artery is a hemodynamically critical state. We aimed to (1) analyze dynamic cerebral autoregulation (DCA) in affected patients, and (2) to correlate DCA data with different collateral flow patterns.
Methods:
DCA was assessed noninvasively by transfer function analysis (phase shift) of respiratory-induced oscillations at 0.1 Hz of arterial blood pressure (Finapres method) and cerebral blood flow velocity (transcranial Doppler) in 30 patients with severe bilateral carotid stenosis (> or =75%) or occlusion. CO(2)-reactivity was measured via inhalation of 7% CO(2). 30 patients with unilateral stenosis were recruited as controls.
Results:
Patients with bilateral 75-89% stenosis had a virtually preserved phase shift. A pronounced reduction was found in bilateral critical stenosis or obstruction (90-100%). Patients with ipsilateral 90-100% and contralateral 75-89% stenosis had a significantly less severe reduction of phase shift on the ipsilateral side. CO(2)-reactivity showed a less marked reduction in patients with bilateral critical stenosis or occlusion. Phase shift was best if "Willisian" collaterals were present. Significantly reduced values were found if only secondary collaterals (ophthalmic artery, leptomeningeal flow) were detected. Poorest values occurred with recruitment of functionally stenosed "Willisian" collaterals. CO(2)-reactivity showed poor values with sole recruitment of secondary collaterals, whereas functionally stenosed primary collaterals did not show values as poor as for phase shift. Clinically symptomatic patients had significantly lower phase shift and CO(2)-reactivity values.
Conclusions:
DCA is severely impaired in bilateral critical carotid stenosis or occlusion. Sole recruitment of secondary collaterals and signs of a functional stenosis in primary ("Willisian") collaterals reflect insufficient collateral supply with a poor hemodynamic status. CO(2)-reactivity assessing the vasodilatory reserve and DCA represent different information for characterizing cerebral hemodynamic impairment. Determining transfer function phase might be a physiologically well supported approach for analysis of cerebral hemodynamic compromise.
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