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Evaluation of impaired dynamic cerebral autoregulation by the Mueller manoeuvre
1Department of Neurology and Clinical Neurophysiology, University Clinics of Freiburg, Germany.
Insights
The Mueller manoeuvre can detect impaired dynamic cerebral autoregulation (dCA) in carotid stenosis patients. This method correlates with other dCA measures, offering a convenient way to assess cerebral haemodynamics.
Area of Science:
- Neurology
- Cardiovascular Physiology
- Medical Diagnostics
Background:
- Arterial blood pressure (ABP) exhibits complex changes during the Mueller manoeuvre (MM), a voluntary negative intrathoracic pressure test.
- Dynamic cerebral autoregulation (dCA) is crucial for maintaining stable cerebral blood flow, and its impairment is associated with carotid artery stenosis.
Purpose of the Study:
- To investigate if MM-induced changes can detect impaired dCA in patients with carotid stenosis.
- To assess the correlation between MM-derived dCA measures and established methods like transfer function phase and CO2-reactivity.
Main Methods:
- 13 patients with severe unilateral carotid stenosis and 16 controls underwent 15-second MM at -30 mmHg.
- Bilateral transcranial Doppler sonography (TCD) and non-invasive ABP monitoring (Finapres) were used.
- An autoregulation index from the MM (mROR) was derived and compared with transfer function phase and CO2-reactivity.
Main Results:
- Patients with carotid stenosis showed a delayed cerebral blood flow velocity (CBFV) reincrease on the affected side during MM compared to controls.
- The affected side exhibited a flatter, more inertial CBFV amplitude response.
- mROR, phase shift, and CO2-reactivity were significantly reduced on the affected side in patients, with strong correlations between mROR and the other measures.
Conclusions:
- The distinct cerebral hemodynamic pattern during MM in carotid stenosis patients suggests impaired dCA.
- The MM is a practical tool for grading compromised cerebral hemodynamics in carotid stenosis.
- MM-derived indices correlate well with established dCA assessment methods.
Abstract:
Arterial blood pressure (ABP) shows polyphasic changes during the Mueller manoeuvre (voluntary negative intrathoracic pressure). The aim of the present study was to investigate (1) whether these changes could be applied to detect impaired dynamic cerebral autoregulation (dCA) in carotid stenosis and (2) whether the degree of indicated impairment correlates with transfer function phase as another current measure for dCA (deep breathing method) and CO2-reactivity. We examined 13 patients with severe unilateral carotid artery stenosis and 16 age-matched controls during 15-s Mueller manoeuvres (MM) at -30 mmHg using bilateral transcranial Doppler sonography and non-invasive ABP recordings (Finapres, 2300, Ohmeda, Englewood, CO, USA). After an initial biphasic oscillation, cerebral blood flow velocity (CBFV) and ABP decreased to below baseline. CBFV reincreased in controls and on contralateral sides in patients 6.0 s (3.8-9.5 s, median and range) after the onset of the decrease, despite a further fall in ABP. CBFV over the affected side revealed a significantly delayed reincrease (8.0 (5.6-10.3) s; P<0.01) combined with a relatively flat and inertial amplitude behaviour. An applied autoregulation index derived from the MM (mROR), phase shift and CO2-reactivity were severely reduced on the affected side in patients (P<0.01). Reduction of the mROR correlated significantly with reduction of phase shift (r=0.69; P=0.002) and CO2-reactivity (r=0.78; P=0.002). In conclusion, the different cerebral haemodynamic pattern during the MM in patients is likely to reflect impaired dCA. The degree of indicated impairment correlates with that of transfer function phase and CO2-reactivity. Therefore, the MM represents a convenient method for grading of compromised cerebral haemodynamics in patients with carotid artery stenosis.