Evaluation of the Link Between Carotid Arterial Wall Viscosity and Major Neurocognitive Disorders

Condition(s) studied

Investigational drug(s) / intervention(s)

Assessment of carotid wall viscosity in patients with vascular dementia: Carotid wall viscosity will be assessed by simultaneous and continuous measurement by 2 operators of local pressure and diameter at the level of the right and left carotids by coupling echotracking (Vevo 3100®) with applanation tonometry (Millar®). 3 successive measurements will be carried out. These measurements will establish the diameter-pressure relationship and its analysis will allow the calculation of wall viscosity by measuring the area under the curve of this relationship during the cardiac cycle.

Assessment of carotid wall viscosity in patients with Alzheimer's disease: Carotid wall viscosity will be assessed by simultaneous and continuous measurement by 2 operators of local pressure and diameter at the level of the right and left carotids by coupling echotracking (Vevo 3100®) with applanation tonometry (Millar®). 3 successive measurements will be carried out. These measurements will establish the diameter-pressure relationship and its analysis will allow the calculation of wall viscosity by measuring the area under the curve of this relationship during the cardiac cycle.

Assessment of carotid wall viscosity in patients not presenting dementia.: Carotid wall viscosity will be assessed by simultaneous and continuous measurement by 2 operators of local pressure and diameter at the level of the right and left carotids by coupling echotracking (Vevo 3100®) with applanation tonometry (Millar®). 3 successive measurements will be carried out. These measurements will establish the diameter-pressure relationship and its analysis will allow the calculation of wall viscosity by measuring the area under the curve of this relationship during the cardiac cycle.

Study summary

The mechanical behavior of conductance arteries is viscoelastic. While the elastic component has been extensively studied, the viscous component has often been neglected for methodological reasons and also because it was considered weak.

Unlike a purely elastic solid, which exhibits instantaneous deformation/relaxation upon application/discontinuation of a force, a viscoelastic solid is characterized, from a mechanical point of view, by a delay between the application or discontinuation of the force and deformation. Thus, at the arterial level, the elasticity of the arterial wall allows the internal diameter to increase proportionally to the blood pressure during systole. The viscous component will induce a delay in diameter restoration, resulting in a larger diameter at each pressure level during the diastolic phase compared to the systolic phase. This results in a shift between the systolic and diastolic curves of the pressure-diameter relationship, creating a hysteresis loop. From a thermodynamic point of view, while a purely elastic material fully restores the energy stored during the loading phase, viscoelastic arteries will incompletely restore this energy. Thus, the surface of the hysteresis loop reflects the energy dissipated during each cardiac cycle (WV), and the area under the loading phase curve represents the energy stored by the arterial wall (WE) during the latter. Thus, arterial wall viscosity (APV) can be expressed either as the absolute value of WV or as a function of the stored energy (WV/WE). Physiologically, this energy loss is low. Its increase could be accompanied by excessive energy dissipation, leading to increased cardiac work and cardio-circulatory decoupling. Conversely, low parietal viscosity could lead to damage to peripheral organs by excessive transmission of pulsatile energy to the periphery due to lack of damping.

Eligibility

Primary outcome measure(s)

• Evaluation of the difference in relative arterial wall viscosity value of the common carotid artery of patients with vascular dementia compared to that of patients with Alzheimer's disease — Day 1
  Carotid wall viscosity will be assessed using a method developed in the pharmacology department, involving simultaneous and continuous measurement by two operators of local pressure and diameter at the right and left carotid arteries, combining echotracking (Vevo 3100®) with applanation tonometry (Millar®). Three successive measurements will be performed. These measurements will establish the diameter-pressure relationship, and their analysis will allow calculation of wall viscosity by measuring the area under the curve of this relationship during the cardiac cycle. The primary outcome measure will be the difference in carotid arterial wall viscosity between the two groups of subjects; it will be studied by analysis of variance (ANOVA).
• Evaluation of the difference in relative arterial wall viscosity value of the common carotid artery of patients with vascular dementia compared to that of patients not presenting dementia — enrollment visit
  Carotid wall viscosity will be assessed using a method developed in the pharmacology department, involving simultaneous and continuous measurement by two operators of local pressure and diameter at the right and left carotid arteries, combining echotracking (Vevo 3100®) with applanation tonometry (Millar®). Three successive measurements will be performed. These measurements will establish the diameter-pressure relationship, and their analysis will allow calculation of wall viscosity by measuring the area under the curve of this relationship during the cardiac cycle. The primary outcome measure will be the difference in carotid arterial wall viscosity between the two groups of subjects; it will be studied by analysis of variance (ANOVA).

Trial sites (1)

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