Arterial pulse wave velocity (PWV) is the speed at which the pulse wave travels through the arterial system. It is recognised as the gold standard for evaluating the stiffness of the arteries in clinical practice. This is essential because arterial stiffness is regarded as an important independent predictor of cardiovascular disease. [1] In this article, we will take a look at what PWV is, why it is important and how to measure it. You can also watch a video instead of reading!
In this blog you will learn:
- What is pulse wave velocity?
- Why is pulse wave velocity clinically important?
- How to measure pulse wave velocity?
What is pulse wave velocity?
Pulse wave velocity is the speed of the pressure wave along the arterial tree. People often assume that it is the speed of the blood through the arteries, but this is incorrect. In a river, the water can move at a certain speed, but the waves generated by wind or boats have a different speed. In the arterial tree, rhythmic waves are initiated by the blood pump – the heart. [2]
When the heart contracts (systole), it generates a pulse wave (or pressure wave) that travels through the arteries at a speed (or velocity) that depends on arterial properties.
Therefore, PWV is the distance of a specific arterial segment divided by the time it takes for the pulse wave to travel on that segment. It is expressed in m/s, and we can measure it on different segments of the arterial tree. For instance, brachial-ankle pulse wave velocity (baPWV) shows how fast the pulse wave travels from the brachial artery (in the arm) to the ankle. Carotid-femoral PWV (cfPWV) is the travel speed of the pulse wave from the carotid to the femoral artery.
Sandrine Millasseau, PhD, explains pulse wave velocity and its significance in this video, followed by a measurement demonstration:
Why is pulse wave velocity clinically important?
PWV provides important information on the state of the arteries. In contrast to pipes from our everyday life, which are made of concrete or metal, the arterial wall of large arteries consists of elastin fibers. In this way, the aorta has a buffering role, storing energy during the heart contraction (systole) and releasing it for the rest of the cardiac cycle. [2]
As we age, the elastin fibers break down (get damaged), which reduces their elasticity. Collagen, a stiffer component, gradually replaces the elastin fibers. This is a normal process, but it can be considerably accelerated by cardiovascular risk factors (e.g. smoking, obesity, hypertension, diabetes), oxidative stress, chronic inflammation, DNA damage and so on. CV risk factors can result in the media calcification of the arterial wall. Increased arterial ageing reflects in greater arterial stiffness and higher pulse wave velocity.
Arterial stiffness is an independent predictor of cardiovascular morbidity and mortality. It is a risk factor for various cardiovascular complications or events; this makes it a cause for concern. Consequently, measurement of pulse wave velocity is essential and should become part of clinical routine, e.g. like cholesterol measurement. It namely shows the total impact of various types of damage to the arterial wall. PWV is considered as an integrative biomarker: it reflects the combined influence of multiple factors on arterial health and function.
Research conducted over the past decade shows that each 1 m/s increase in PWV corresponds to a 12-14% rise in overall cardiovascular mortality (i.e. having a serious cardiovascular event and dying from it), as evident from the example below: [4]
Furthermore, the 2018 ESC/ESC Guidelines for the Management of Arterial Hypertension classify a carotid-femoral PWV above 10 m/s as asymptomatic organ damage. [5]
How do we measure pulse wave velocity?
Technological developments over the last few years have made the measuring of PWV a lot easier than before. According to the Expert Consensus Document on Arterial Stiffness (2006), “the measurement of PWV is generally accepted as the most simple, non-invasive, robust, and reproducible method to determine arterial stiffness”. [2] Carotid-femoral PWV (cfPWV) is also regarded as a “gold-standard” measurement of arterial stiffness. [3]
The technologies that have enabled the research leading to the recognition of pulse wave velocity as an independent marker of cardiovascular disease are not appropriate for clinical routine. They require expertise, are quite expensive and the examination is time-consuming.
For measuring PWV in clinical routine, the technology needs to offer the following advantages:
- Simplicity
- Ease of use
- Fast assessment (to fit into standard consultation time)
- Little expertise required
- Acceptable to the patient (non-invasive)
One of the latest-generation devices for measuring PWV in primary care is the MESI mTABLET ABI with the PWV app. It requires no expertise to operate. The exam is fully automated and only takes a few minutes. For this reason, it can be routinely performed in risk groups threatened by cardiovascular disease – diabetics, overweight people, hypertensives, people over 65, etc. For these groups, peripheral arterial disease (PAD) screening with the measurement of the Ankle-Brachial Index (ABI) is also recommended. With MESI mTABLET ABI, the measurement of PWV is performed at the same time as ABI, displaying the following results:
- Ankle-Brachial Index
- interarm blood pressure comparison
- brachial-ankle pulse wave velocity (baPWV)
- carotid-femoral pulse wave velocity (cfPWV)
- the PWV reference value graph and
- the assessment of the patient’s arterial age.
The MESI mTABLET ABI with PWV app provides an advanced arterial assessment, allowing medical professionals to determine further treatment in a fast and effective way.