Arterial pulse

Main characteristics of the arterial pulse

When evaluating arterial pulsation, several key parameters are considered that reflect cardiac function and the state of the vascular bed:

• Frequency. Directly determined by the heart rate (HR).
• Rhythm. Can be regular or irregular. This indicator demonstrates the regularity of cardiac activity.
• Amplitude. Characterizes the stroke volume of blood and the degree of elasticity of the arterial walls.
• Velocity (speed). Reflects the rate at which pressure in the arteries changes (rises and falls) during left ventricular contraction. The pulse can be fast or slow.
• Tension. Assessed by the resistance of the arterial wall—determined by the pressing force required to completely compress the vessel and stop pulsation. By tension, the pulse is divided into hard and soft.

Sphygmography: graphical registration of the pulse

Sphygmography is a method for graphically recording the arterial pulse. The resulting curve (sphygmogram) consists of first-order waves, each corresponding to a specific phase of the cardiac cycle.

The mechanism behind the formation of these waves is based on the stretching of the aortic wall during blood ejection and its subsequent return to its original dimensions due to elasticity.

Main elements of the sphygmogram:

1. Anacrotic wave (anacrota) — the ascending part of the curve (rise). It reflects the moment the semilunar valves open and blood is actively ejected into the aorta. The duration of this stage is about 0.08 s.
2. Systolic plateau — the peak of the pulse curve, lasting approximately 0.14 s. The total period of systolic rise and plateau takes about 0.25 s.
3. Catacrotic wave (catacrota) — the descending part of the curve (fall), which shows the drop in pressure in the arterial system during diastole. The period of diastolic decline lasts about 0.4 s.
4. Incisura (notch) — a sharp, short-term drop on the catacrota. This element precisely corresponds to the moment the aortic semilunar valves snap shut.
5. Dicrotic notch (wave) — a secondary, lower-amplitude wave rise immediately following the incisura. It is caused by elastic recoil: blood rebounds from the closed aortic valves back into the vascular bed.

Propagation of the pulse wave

The mechanical vibration, originating in the aorta, is transmitted to the arteries and arterioles. The propagation velocity of the pulse wave is always higher than the velocity of the blood flow itself.

To calculate the pulse wave velocity, a special formula is used that takes into account the physical characteristics of the vessel:

• Internal radius of the vessel.
• Thickness of the vessel wall.
• Density of blood and the vessel wall.
• Modulus of elasticity (compliance) of the vessel.

For example, when recording the pulse at the radial artery (a. radialis), the distance to which from the heart is about 1 meter, the transit time of the wave is approximately 100 ms. It is by this time that the pulsation at the wrist lags behind myocardial contraction.

As the wave progresses from the heart to the periphery, pressure oscillations gradually attenuate. However, the amplitude of each pulse phase in peripheral arteries increases (the phenomenon of peripheral pulse amplification occurs). Final attenuation of the pulse wave occurs in the arterioles.

Venous pulse (using the jugular vein as an example)

In addition to the arterial pulse, there is a venous pulse, which is recorded in large veins (e.g., jugular) and correlated with the electrocardiogram (ECG). The venous pulse curve has a complex structure and consists of positive and negative waves.

Positive waves:

• Wave a: arises due to right atrial systole, causing impaired outflow and partial blood return.
• Wave c: transmitted pulsation (mechanical shock) from the adjacent carotid artery.
• Wave v: reflects right atrial filling and blood stagnation when the tricuspid valve is closed.

Negative waves (collapses):

• x-collapse: rarefaction in the atria at the beginning of ventricular systole (valve plane shifts toward the apex) and active venous blood inflow.
• y-collapse: corresponds to the rapid right ventricular filling phase upon opening of the tricuspid valve and rapid emptying of the veins.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Formula for calculating pulse wave velocity and the influence of the elasticity modulus
• The phenomenon of peripheral pulse amplitude amplification
• Mechanisms of venous pulse wave formation
• Synchronization of ECG elements and sphygmogram waves

Other topics in "Vascular Bed Hemodynamics"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.