Pulse Wave

When the heart contracts a volume of blood is squeezed into the aorta, causing it to stretch to accommodate this new blood volume. Then, as the vessel walls return to normal, blood is pushed from the aorta through the arteries.

This process of expansion and returning to normal repeats with each beat of the heart as blood travels through your arteries.

Wave Patterns & Elasticity

Imagine your blood as a strand of pearls being pulled through a much smaller rubber tube. This illustrates circulation not as a series of single beats, but as a wave pattern of blood flow. This simplified version of a complex process does not take into account fluid dynamics, but it does illustrate two points: 1) wave patterns and 2) the importance of arterial elasticity.

Now imagine dropping a stone into a calm lake. Think of the concentric circles traveling away from the point where the stone entered the water. Assuming no interference, these waves would travel unchanged to the other side of the lake. If these waves encountered a rock or log along the way, they would bend around the obstruction, thus altering the wave pattern.

In our arteries these rocks and logs represent build-ups inside the lining of the artery, or a stiffening of the artery wall, which are precursors to atherosclerosis and arteriosclerosis. By analyzing the alterations of a pulse wave one can glean a tremendous amount of information about the health and elasticity of an individual’s arterial system.

Measuring Pulse Waves

The analysis of the pulse wave consists of measuring the relationship between the forward traveling waves created by the contraction of the heart and reflected waves that travel back towards the heart created by resistance of the arteries. These two wave forms overlap each other to form the pulse wave.

As an individual loses elasticity in their arteries the reflected resistance waves increase in intensity, further altering the pulse wave and these changes can be measured.

There are primarily two different ways that you can non-invasively measure pulse waves. The first is to measure the movement of the artery walls and the second is to measure the flow of blood through the artery and then, from those measurements, estimate the movement of the artery wall.

Research facilities and hospitals generally utilize technologies that specifically measure the artery walls because it is through this type of measurement that the greatest level of precision and accuracy is obtained.

Features of the Pulse Waveform

The arterial pulse waveform has 2 components: the first is the forward traveling wave when the left ventricle contracts, and the second is the reflected wave returning from the periphery. Ideally, for a young person whose arterial tree is generally soft and compliant, the reflected wave coincides with the diastole phase of the cardiac cycle and augments perfusion of the coronary arteries.