#### Pulse Wave Velocity

The pulse wave velocity is defined as the ratio between the length of an arterial segment and the related transit time of the pressure wave: PWV = Distance / DeltaT.
WPulsePen software allows the PWV assessment employing the two main methods used to measure the distance:
1) adjusted "direct" method;
2) the "subtractive" method.
Adjusted "direct" method:
An expert consensus document on the measurement of aortic stiffness suggests the usage of 80% of the direct Carotid-to-peripheral Artery tape measured distance as the new standard for daily practice: recommended distance = (direct Carotid-to-peripheral Artery) x 0.8.
[(Carotid <> Peripheral Artery) * 0.8]
The graph shows the reference values of the pulse wave velocity in the Aorta [aPWV]. Data are shown as percentile curves related to age and have been collected on adult, healthy, free from overt cardiovascular diseases and cardiovascular risk factors population, using the PulsePen tonometer. The distance is measured by the 'direct' method (Carotid-to-Femoral distance) x 0.8.
In the above example, the direct Carotid-to-Femoral distance is 690 mm, thus PWV is 16.9 m/s: this value of PWV is higher than the 95th percentile according to the age (62 years).
The data shown in the graph can be interpreted as follows:
• the values below the 75th percentile may be considered as normal values;
• Between the 75th and 95th percentile: border-line values. It is advisable to periodically repeat the measurement and to try to identify the causes of increased arterial stiffness;
• Above the 95th percentile: evidence for ‘‘arterial stiffness’’. High risk for cardiovascular disease.
To switch between displaying the PWV measured by the "direct" method to the PWV measured by the "subtractive" method, you must select the green area on the left of the figure.
"Subtractive" Method:
The subtractive method is based on the consideration that, while the pressure wave reaches the Carotid pressure landmark, it would cover the same distance in the Aorta. This path coincides with the distance between the Suprasternal notch and the Carotid sampling site.
Distance "Subtractive Method" = (from Suprasternal notch to peripheral Artery) - (from Suprasternal notch to Carotid).
[(sS.N. <> Peripheral Artery) - ( Carotid <> sS.N.)]
The graph shows the reference values of the pulse wave velocity in the Aorta [aPWV]. Data are shown as percentile curves related to age and have been collected on adult, healthy, free from overt cardiovascular diseases and cardiovascular risk factors population, using the PulsePen tonometer. The distance is measured by the 'subtractive' method.
In the above example, the distance from the Suprasternal notch to Femoral Artery is 600 mm and the Suprasternal notch to Carotid distance is 100 mm, thus PWV is 15.3 m/s: this values of PWV is higher than 95th percentile according to the age (62 years).
To switch between displaying the PWV measured by the "subtractive" method to the PWV measured by the "direct" method, you must select the amaranth area on the left of the figure.