Pulse wave

Dynamics and propagation in the vascular bed

When the pulse wave propagates from the heart to the periphery, the following phenomena are observed:

• Pressure attenuation — pressure fluctuations gradually decrease.
• Peripheral pulse augmentation — the amplitude of each pulse phase in peripheral arteries increases.
• Disappearance of the pulse — the mechanical oscillation finally attenuates in the arterioles. The pulse is absent in capillaries, venules, as well as small and medium veins.

What elements does a sphygmogram consist of?

To study the pulse wave, sphygmography is used — a method for the graphical recording of the arterial pulse. The sphygmogram distinguishes elements, or 1st-order waves:

• Anacrote.
• Catacrote.
• Incisura.
• Dicrotic wave.

Role in the baroreceptor reflex

The pulse wave participates in the pressor-depressor reflex. The chain of events is as follows:

1. A positive inotropic effect leads to an increase in cardiac output.
2. The pulse wave stimulates the baroreceptors of the aortic arch and carotid sinuses.
3. Afferenation to the nucleus of the solitary tract increases.
4. Secondarily, the tone of the vagus nerve nucleus increases.

Clinical significance: pulse deficit

In rhythm disorders, particularly in atrial fibrillation, a pulse deficit (pulsus deficiens) may occur. This is the difference between the heart rate (HR) determined by auscultation and the pulse rate determined by palpation over a peripheral artery, such as the radial artery.

• Mechanism of development: Diastolic pauses of varying duration lead to different left ventricular filling and fluctuations in stroke volume. During some contractions, the systolic output is so small that the pulse wave does not reach the periphery and is not palpable.
• Clinical picture: The patient may feel palpitations and "skipped beats". Upon palpation, the pulse is irregular (arrhythmic), pulse waves vary in filling, which makes rate calculation difficult.
• Calculation example: If the auscultatory HR is 90 per minute, and only 72 beats are palpated at the radial artery, the pulse deficit is 18.

Artificial pulse wave during resuscitation

In clinical death, an artificial pulse wave is created using closed-chest cardiac massage.

• Mechanism: The heart is compressed between the sternum and the spine, which forces blood into the major vessels. For this, the chest is compressed with an energetic push by 1/3 of its anteroposterior diameter, i.e., by 3–5 cm. After the push, the hands are relaxed without lifting them off the chest so that the heart chambers fill with blood again.
• Control of effectiveness: During the massage, an artificial pulse wave must be palpable in major vessels — the carotid or femoral artery. Every 2–3 minutes, compressions are interrupted for a few seconds to check for the appearance of a spontaneous pulse.
• Medication support: Epinephrine (adrenaline) is administered to increase the effectiveness of the massage and stimulate spontaneous contractions. It increases vascular tone, increases blood flow, and enhances myocardial tone.

Class and exam questions

What else to study on this topic

• Sphygmography
• Baroreceptor reflex
• Cardiac output
• Atrial Fibrillation
• Cardiopulmonary resuscitation

Other topics in "Physiology concepts"

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