Pulse wave velocity (PWV) is the speed at which the pressure wave travels through the arteries. It is a physiologic parameter that provides information regarding pathologic arterial stiffness (stiffness of arterial vessels) as well as information about endothelial function (layer of cells on the inner surface of blood vessels). With age, vascular stiffness and thus pulse wave velocity naturally increase. This is due to remodeling processes, whereby elastic connective tissue in elastic arteries such as the aorta is replaced by collagenous connective tissue. Above all, however, diseases that promote or cause atherosclerosis (hardening of the arteries) are significantly involved in this process. The measurement of pulse wave velocity enables the assessment of cardiovascular risk factors. Diseases that promote atherosclerosis or in which alterations in pulse wave velocity may be present:
- Obesity
- Arterial hypertension (high blood pressure)
- Chronic renal insufficiency (chronic renal failure).
- Diabetes mellitus (diabetes)
- Hypercholesterolemia
- Hyperuricemia (gout)
- Coronary artery disease (CAD; coronary artery disease).
- Nicotine abuse (heavy smoking)
Indications (areas of application)
Measurement of pulse wave velocity is used to assess pre-existing end-organ damage in the vascular system (vascular system) as a result of the above diseases. It allows the establishment of a risk profile and, as a consequence, therapeutic measures should be initiated for the treatment of these diseases.
Before the examination
Pulse wave velocity measurement is a noninvasive diagnostic method that does not require any preparation of the patient.
The procedure
Pulse wave velocity is expressed in meters per second and describes the speed at which blood pressure wave generated by contraction of the heart travels through the arterial vascular system. Compared to the flow velocity of blood, the velocity of pulse waves is higher. The decisive parameter for the pulse wave velocity is the elasticity of the vessel. The more rigid the vessel wall, the faster the pulse wave. Due to the different size and wall structure of the vessels of the arterial system, the pulse wave velocity is different depending on the location. In the aorta, which is very elastic, it is 4-6 m/s. In the peripheral vessels, the pulse wave velocity increases to 8-12 m/s due to increased stiffness and smaller vessel lumina. The pulse wave velocity is calculated on the basis of a measurement of the pulse wave at two measurement points of a continuous vessel section. The time delay of the arrival of the pulse wave at the measurement points is recorded. This time is set in relation to the distance between the two measuring points, so that a velocity can be calculated. Practically, two pressure pulse meters are placed at the mentioned measuring points (e.g., in the course of the leg arteries), which detect the pulse wave. The calculation is based on the following formula (PWG: pulse wave velocity; B, A: measurement points): PWG (m/s) = distance/time (B-A).
Interpretation
If pulse wave velocity is increased, pulse wave reflection in the periphery favors an increase in systolic blood pressure (first value in a blood pressure measurement) and consequently a decrease in diastolic blood pressure (second value in a blood pressure measurement). As a consequence, this leads to an increased workload of the heart during systole (heart ejection phase), as well as to a decreased coronary perfusion in diastole (decrease in blood flow to the coronary vessels, which are perfused in diastole (heart filling phase)). Thus, pulse wave velocity represents a critical factor in the assessment of arterial vascular stiffness. With age, the proportion of elastic fibers within the vessel wall decreases and is replaced by collagenous connective tissue, making the vessels stiffer. Existing arteriosclerosis also significantly increases vascular stiffness. Pulse wave velocity is of critical importance, as it is associated with increased mortality (morbidity) in patients when the velocity is significantly increased.In several studies, an increase in pulse wave velocity of as little as 1 m/s has been associated with increased mortality (death rate) by 10-39%.
