Direct Measurement of Local Arterial Stiffness and Pulse Pressure
Arterial stiffness differs between different sites in the arterial tree. It can, therefore, be of interest to know the stiffness at a particular arterial site. Local arterial stiffness assesses stiffness at a cross section of an artery. At present echo-tracking methods are the gold standard to measure local wall properties of superficial arteries. This technique measures with very high precision the diameter and diameter change of a cross section of an artery. For deep arteries like the aorta, CT and MRI techniques have been developed. Although less than echo tracking, the accuracy of these latter techniques increased over recent years. Assuming the cross section being circular, the change in cross-sectional area can be calculated from diameter and diameter change. From the change in cross-sectional area and change in pressure, the local vessel wall properties distensibility coefficient (DC) and cross-sectional compliance (CC) can be calculated. Distensibility is a measure of wall elasticity and the inverse of stiffness. Compliance reflects the buffering capacity of the artery. Local stiffness assessment is the only method that can assess both wall properties. In addition, if the pressure curve is available, the full pressure–diameter relation can be shown and wall properties at a particular pressure or pressure range (isobaric conditions) can be calculated. Alternative methods have also been developed and are briefly discussed. The major source of error in calculating local arterial stiffness comes from the assessment of the arterial pressure at the same arterial site. Different methods to calculate this local pressure are discussed.
KeywordsLocal arterial stiffness Distensibility Compliance Pulse pressure Local blood pressure Methods
The authors thank Dan De Vos, MD, for his contribution on MR imaging.
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