Table 1: Summary of clinical studies evaluating cerebrovascular reserve in patients with internal carotid artery atherosclerotic lesions.
| Author, year | Type of study | Number of patients | Clinical course of desease | Severity of ICA lesion | CO2-reactivity | DCA assessment | Blood flow measurement | Findings |
| Ringelstein E [10] | Cohort | 40 | Asymptomatic/ Symptomatic | Occlusion | Vasodilatory response of CO2/ acetazolamide, hyperventilation | – | TCD | The difference between vasomotor reactivity for symptomatic and asymptomatic unilateral occlusions was highly significant. |
| Kleiser B [17] | Cohort | 85 | Asymptomatic/ Symptomatic | Occlusion | Inhalation of 5% CO2, hyperventilation | – | TCD | CO2 test is a valuable method of estimating the risk of stroke in patients with carotid artery occlusions. |
| Yonas H [18] | Cohort | 68 | Symptomatic | Stenosis ≥ 75% or occlusion | Acetazolamide | – | Xe/CT | Compromised CO2 reactivity accompanied by relatively low initial flow significantly increased incidence of ipsilateral stroke. |
| Gur A [19] | Cohort | 44 | Asymptomatic | Stenosis ≥ 70% or occlusion | Acetazolamide | – | TCD | Statistically significant correlation between cerebral ischemic events and impaired cerebral vasomotor reactivity |
| White R [12] | Cohort | 27 | Asymptomatic | Stenosis ≥ 60% or occlusion | Inhalation of 8% CO2 | Autoregulation index (ARI) with cuff-test | TCD | ARI significantly reduced in ipsilateral MCA compared with normal controls and nonstenosed carotid arteries in patients. |
| Hu H., 1999 [13] | Cohort | 83 | Symptomatic | Stenosis or occlusion | Inhalation of 5% CO2 | Phase angle between BP and BFV at diiferent frequency ranges (frequency domain) | TCD | Patients with unilateral high-grade carotid stenosis demonstrated significant reduction in LF (0.04-0.15 Hz) phase angle, CO2-reactivity. |
| Vernieri F [24] | Cohort | 104 | Asymptomatic/ Symptomatic | Breath-holding index | – | TCD | Risk of cerebrovascular events occurring during the follow-up period was significantly related to vasomotor reactivity and type of collateral pathway | |
| Reinhard M [8] | Cohort | 101 | Asymptomatic/ Symptomatic | Stenosis ≥ 70% or occlusion | Inhalation of 7% CO2 | PS between BP and BFV at 0.1 Hz (frequency domain) | TCD | Strong association between type of collateral flow and CO2-reactitvity, PS. |
| Reinhard M [11] | Cohort | 139 | Asymptomatic/ Symptomatic | Stenosis ≥ 70% or occlusion | Inhalation of 7% CO2 | PS shift between BP and BFV at 0.1 Hz (frequency domain); Correlation coefficient indexes between BP and BFV (time domain) | TCD | The correlation indexes Dx and Mx were significantly higher ipsilateral to stenosis and increased with degree of stenosis. |
| Reinhard M [14] | Cohort | 58 | Asymptomatic/ Symptomatic | Stenosis ≥ 70% | Inhalation of 7% CO2 | PS shift between BP and BFV at 0.1 Hz (frequency domain); Correlation coefficient indexes between BP and BFV (time domain) | TCD | Reconstructive surgery led to reliable improvement of impaired CO2 reactivity and DCA ipsilaterally in severe carotid stenosis. |
| Tang S [15] | Cohort | 21 | Asymptomatic/ Symptomatic | Stenosis ≥ 50% | – | Correlation coefficient indexes (Mx) between BP and BFV (time domain) | TCD | High correlation between the degree of ICA stenosis and the Mx. It improved significantly after carotid stenting in both moderate and severe ICA stenosis. |
| King A [7] | Cohort Meta-analysis | 106 | Asymptomatic | Stenosis ≥ 70% | Vasodilatory response of CO2 or acetazolamide | – | TCD | No association between impaired CVR and recurrent events, but the study was underpowered because of the low event rate. |
| Gupta A [6] | Meta-analysis | 991 | Asymptomatic/ symptomatic | Stenosis or occlusion | Vasodilatory response of CO2 or acetazolamide | No |
TCD SPECT PET |
CVR impairment is strongly associated with increased risk of ischemic events in carotid stenosis or occlusion. |
| Semenyutin V [16] | Cohort | 35 | Asymptomatic/ Symptomatic | Stenosis ≥ 75% | – | PS shift between BP and BFV at 0.08-0.12 Hz (frequency domain) | TCD | Regardless clinical type of disease various state of DCA may be present in patients with severe ICA stenosis. Surgical reconstruction led to reliable restoration of impaired DCA. |
| Abbreviations: CVR: Cerebrovascular Reserve; ICA: Internal Carotid Artery; DCA: Dynamic Cerebral Autoregulation; PS: Phase Shift; BP: Blood Pressure; MCA: Middle Cerebral Artery; BFV: Blood Flow Velocity; LF: Low Frequency; TCD: Transcranial Doppler; Xe/CT: Xenon Computed Tomography; PET: Positron Emission Tomography; SPECT: Single-Photon Emission Сomputed Tomography | ||||||||