Features of the Pulse Waveform
The arterial pulse waveform is a contour wave generated by the heart when it contracts, and it travels along the arterial walls of the arterial tree. Generally, there are 2 main components of this wave: forward moving wave and a reflected wave. The forward wave is generated when the heart (ventricles) contracts during systole. This wave travels down the large aorta from the heart and gets reflected at the bifurcation or the "cross-road" of the aorta into 2 iliac vessels. In a normal healthy person, the reflected wave usually returns in the diastolic phase, after the closure of the aorta valves. The returned wave give a notch and it also helps in the perfusion of the heart through the coronary vessels as it pushes the blood through the coronaries. Therefore the velocity at which the reflected returns becomes very important: the stiffer the arteries are, the faster it returns. This may then enter into the systolic phase and augment final blood pressure reading. Diagram shown a typical healthy arterial pulse waveform.
Physiology of Pulse Waveform
Pulse Waveform of a 25 year old person
For a normal young person, where the arteries are generally compliant, the slow travelling reflected wave from the peripheral occurs during diastole, thus enhancing perfusion of the coronary arteries.
Pulse Waveform of a 47 year old person
With age, the arteries stiffen. Pulse wave velocity increases and the reflected wave now travels faster and gives rise to a "shouldering" at the primary wave, and occurs during systole. This effect prolongs the systolic cycle increasing the workload and oxygen requirement of the heart muscles. The poor notch also compromises the flow of the coronaries.
Pulse Waveform of a 80 year old person
In the elderly, further arterial stiffening cause the reflected wave to return much faster and gives rise to a "shouldering" at the primary wave; and coincide very close to the systolic peak, resulting in an augmented wave. The heart now needs to contract even harder (to overcome the oncoming reflected wave) and for a longer period. At the same time, coronary artery perfusion is further compromised.