Aortic Pulse Wave Velocity: An Independent Marker of Cardiovascular Risk

Michel E. Safar, MD, Olivier Henry, MD, Sylvie Meaume, MD

Disclosures

Am J Geriatr Cardiol. 2002;11(5) 

In This Article

Measurement of Aortic PWV

PWV may be measured in various segments of the arterial circulation.[3] When two pressure waves are recorded at two different sites of the vascular tree, it is possible, owing to the propagation of the waves, to measure the time delay ( t) and the distance (D) between these two waves. PWV is then defined as D/ t (Figure 1). Measurement of time delay is usually performed by determination of a foot-to-foot transit time.

Pulse wave velocity measurements: A=wave recorded by the proximal transducer; B=wave recorded by the distal transducer; T=time delay between the foot waves; D=distance traveled by the wave

Since the aorta is the major component of arterial elasticity, the carotid-femoral PWV offers the simplest reproducible and noninvasive evaluation of regional stiffness. This measurement allows the recording of the pulse pressure at two different sites of the aorta and the measurement of the distance between the two pressure waves (Figure 1). The former is usually done at the site of the common carotid artery and the femoral artery, using standard blood pressure (or even velocity) transducers, enabling an adequate recording, particularly of the foot of the pressure wave, and therefore, the calculation of the time delay between the carotid and the femoral waves. The latter is the noninvasive measurement of the distance between the carotid and femoral recordings. It is important to recall that an accurate measurement of this distance is obtained only with invasive procedures. In this regard, some authors suggested, for noninvasive measurements, a possible correction based on anatomic dimensions of the body. Others recommended subtracting the distance between the suprasternal notch to the carotid location from the total distance when the carotid pulse pressure is recorded instead of the aortic arch pulse, because of the pulse traveling in the opposite direction. In clinical practice, arteries become longer and tortuous with age, with the result that the path lengths determined from superficial linear measurements are underestimated. Repeatability studies, checks made with Bland and Altman diagrams, and modern computer technology have now made aortic PWV quite feasible for the simple investigation of aortic stiffness in CV epidemiology.[2]

In clinical studies, the principal factors modulating the level of PWV are age, blood pressure and to a lesser extent, gender. These parameters represent more than 50% of the variability of aortic PWV: the higher the age, the higher the pressure, and the higher the aortic PWV. In epidemiologic studies, in order that PWV reflects arterial stiffness independently of age and blood pressure, PWV should be adjusted to these two parameters. This approximation is true below 70 years of age. Above 70 years, aortic PWV is exclusively influenced by blood pressure, but not by age.[4]

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