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Vasomotor reactivity and pattern of collateral blood flow in severe occlusive carotid artery disease
1Department of Neurology, University Hospital of the Saarland, Homburg/Saar, Germany.
Insights
Severe carotid artery disease impacts cerebrovascular autoregulation, which is influenced by collateral pathways. Noninvasive transcranial Doppler ultrasound effectively assesses these pathways and vasomotor reactivity, offering an alternative to invasive methods.
Area of Science:
- Cerebrovascular physiology
- Neurology
- Medical imaging
Background:
- Cerebrovascular autoregulation is compromised in severe occlusive carotid artery disease, depending on collateral pathway function.
- Invasive cerebral angiography has been used to evaluate collateral pathways, but noninvasive methods are preferred.
- Transcranial Doppler ultrasound offers a noninvasive approach to assess collateral pathways and vasomotor reactivity.
Purpose of the Study:
- To evaluate collateral pathways and vasomotor reactivity in patients with severe internal carotid artery disease using transcranial Doppler ultrasound.
- To compare the effectiveness of different collateral pathways in maintaining vasomotor reactivity.
- To establish transcranial Doppler ultrasound as a reliable noninvasive alternative to cerebral angiography for assessing collateral supply.
Main Methods:
- Transcranial Doppler ultrasound was used to evaluate collateral supply through anterior and posterior communicating arteries, ophthalmic artery, and leptomeningeal anastomoses in 48 patients with internal carotid artery occlusion or severe stenosis.
- Ipsilateral vasomotor reactivity was assessed using breath-holding and acetazolamide challenges to measure middle cerebral artery mean blood velocity changes.
- Contralateral internal carotid artery stenosis (50% to <90%) was present in 20 patients.
Main Results:
- Vasomotor reactivity was not affected by contralateral internal carotid artery stenosis.
- Poor vasomotor reactivity was observed when ophthalmic or leptomeningeal pathways accompanied an anterior communicating artery pathway, compared to a lone anterior communicating artery pathway (P < .05).
- Acetazolamide challenge showed better preserved vasomotor reactivity with a lone anterior communicating artery pathway (66%) versus anterior and posterior communicating artery pathways (33%, P < .05), a difference not seen with breath-holding.
Conclusions:
- The presence of an ophthalmic artery pathway may indicate disturbed vasomotor reactivity.
- Transcranial Doppler ultrasound is a reliable noninvasive method for evaluating collateral pathways, suggesting careful consideration of cerebral angiography's use.
- Noninvasive assessment of collateral pathways is crucial for understanding cerebrovascular autoregulation in carotid artery disease.
Background And Purpose:
The compromise of cerebrovascular autoregulation in severe occlusive carotid artery disease depends on the functional capacity of collateral pathways. In previous reports correlating hemodynamic disturbances with collateral pathways, collateral blood supply was often evaluated by invasive cerebral angiography. In this study noninvasive transcranial Doppler ultrasound was used to determine both collateral pathways and vasomotor reactivity.
Methods:
With the use of blood flow direction, compression tests, and evident side-to-side asymmetries of blood velocities, the collateral supply through the anterior and posterior communicating arteries, the ophthalmic artery, and leptomeningeal anastomoses was evaluated by transcranial Doppler ultrasound in 48 patients (42 men, 6 women; mean +/- SD age, 59 +/- 9 years) with occlusion (n = 36) or stenosis of more than 90% (n = 12) of one internal carotid artery. Ipsilateral vasomotor reactivity was determined by the percent increase of middle cerebral artery mean blood velocity with the use of (1) the breath-holding maneuver and (2) acetazolamide (1 g IV) as vasodilatory stimulus. Additional stenoses (50% to < 90%) of the contralateral internal carotid artery were present in 20 of the 48 patients.
Results:
Vasomotor reactivity was not affected by the presence of a contralateral internal carotid artery stenosis. Both vasodilatory stimuli similarly indicated poor vasomotor reactivity when an ophthalmic or a leptomeningeal pathway accompanied an anterior communicating artery pathway compared with a lone anterior communicating artery pathway (P < .05). The acetazolamide challenge indicated significantly better preserved vasomotor reactivity when blood supply was provided through a lone anterior communicating artery pathway (66 +/- 30%) than through an anterior and posterior communicating artery pathway (33 +/- 20%, P < .05), whereas the breathholding method failed to show such a difference.
Conclusions:
The presence of an ophthalmic artery pathway may provide the first evidence of disturbed vasomotor reactivity. The use of cerebral angiography to evaluate collateral pathways must be considered carefully since transcranial Doppler ultrasound is a reliable noninvasive alternative.