It is characterized by a smooth and relatively fast upward stroke and a smooth, more gradual downward stroke, interrupted only briefly at the peak of the pulse.
These palpable pulsatile changes in the diameter of the carotid artery are practically identical to the intraluminal pressure pulse .
Carotid pulse abnormalities can involve an alteration in the amplitude of the peak of the pulse, a distortion of the ascending or descending stroke, or any combination of these changes.
The heartbeat is felt through the walls of a peripheral artery, such as the one felt in the radial artery in the wrist.
Other sites for pulse measurement include the side of the neck (carotid artery), the antecubital fossa (brachial artery), the temple (temporal artery), the anterior side of the hip bone (femoral artery), the posterior part of the knee (popliteal artery) and instep (dorsal artery of the foot).
What is felt is not the blood pulsing through the arteries (as is commonly assumed), but rather a shock wave that travels along the walls of the arteries as the heart contracts.
This shock wave is generated by the pounding of blood as it is ejected from the heart under pressure. It is analogous to the hammering sound heard in steam pipes as steam is forced into the pipes under pressure.
A pulse in the veins is too weak to feel, although it is sometimes measured with a sphygmograph; the tracing obtained is called a phlebogram.
When taking a pulse, the frequency, rhythm, and strength or amplitude of the pulse are observed. The average rate in an adult is between 60 and 100 beats per minute. The rhythm is checked for possible irregularities, which can be an indication of the general condition of the heart and circulatory system.
The amplitude of a pulse can vary from totally impalpable to a limit and full; however, these terms are imprecise and subject to misinterpretation.
To provide a more standardized description of pulse width, some agencies and hospitals use a scale that provides a more objective assessment and reporting of the strength of a pulse. On such a scale zero would mean that the pulse cannot be felt.
+1 would indicate a weak, threadlike pulse that is difficult to palpate, fades in and out, and clears easily with light pressure.
+2 would be a pulse requiring light palpation, but once located it would be stronger than +1.
+3 would be considered normal; and a +4 pulse would be one that is strong, bounding, easily palpated, and perhaps hyperactive, and could indicate a pathological condition such as aortic regurgitation.
If a pulse is noted to be weaker during inhalation and stronger during exhalation (paradoxical pulse), this could indicate a greater reduction in blood flow to the left ventricle than normal, as in constrictive pericarditis or pericardial effusion. or an exaggerated inspiratory maneuver, as in tracheal obstruction, asthma, or emphysema.
An instrument for recording the movements, shape, and strength of the arterial pulse is called a sphygmograph. The sphygmographic tracing (or pulse tracing) consists of a curve that has a sudden rise (primary rise) followed by a sudden drop, after which there is a gradual decline marked by a number of secondary rises.
The carotid arteries
The carotid arteries are major blood vessels in the neck that supply blood to the brain, neck, and face. There are two carotid arteries, one on the right and one on the left. In the neck, each carotid artery branches into two divisions:
- The internal carotid artery supplies blood to the brain.
- The external carotid artery supplies blood to the face and neck.
Like all arteries, the carotid arteries are made of three layers of tissue:
- Intimate, the smoothest inner layer.
- Means, the muscular middle layer.
- Adventitia, the outer layer.
The carotid sinus or carotid bulb is a widening of a carotid artery at its main branch point. The carotid sinus contains sensors that help regulate blood pressure . The pulse of the carotid artery can normally be felt in the neck by pressing the fingertips against the side of the windpipe or windpipe.
Carotid arterial pulses are usually examined with the patient supine and the patient’s trunk slightly elevated. The patient’s chin should be elevated to allow easy palpation and yet not high enough to tighten the neck muscles.
During pulse palpation, the examiner uses touch or mechanoreceptor sensors on the fingertips to detect movement of the arterial wall associated with the pressure pulse as it passes through the palpation site.
The fingers should be placed between the larynx and the anterior border of the sternocleidomastoid muscle at the level of the cricoid cartilage. When palpating the pulse, the degree of pressure applied to the artery should be varied until the maximum pulsation is appreciated.
Opinions vary as to how many and which fingers to use and as to the proper positional relationship between the patient and the examiner. Some clinicians believe that tactile stimulation is accentuated using a single finger and may even prefer to use the thumb.
Others absolutely prohibit the use of the thumb for palpation and favor the use of two or three fingers. Whichever finger or combination of fingers is used, it is essential that the examiner determines that he is not sensing his own pulse at the fingertip.
This possible error can be detected by pressing down with a finger on an adjacent body site that does not overlap the patient’s artery. The examiner is more likely to feel his own pulse if he uses his thumb.
In general, the carotid artery is palpated with the examiner sitting or standing comfortably on the right side of the patient. However, some physicians prefer to examine the carotid pulsations while standing at the head of the patient’s bed.
Because simultaneous palpation of the carotid artery and auscultation of the heart is occasionally beneficial, it seems preferable for the examiner to position himself on the right side of the patient.
Palpation of an arterial pulse can be aimed at assessing cardiac output, determining heart rate and rhythm, establishing the integrity of the peripheral arterial blood supply, or locating peripheral lesions.
The carotid pulse examination is generally aimed at assessing the condition of the heart. Although palpation of the carotid pulse is the most important component, the examination should also include inspection and auscultation.
The absence of visible carotid pulsations suggests a marked decrease in the amplitude of the carotid pulse. The presence of a murmur can be a clue to partial carotid obstruction or it can be a sound transmitted by a heart murmur.
Generally, the brachial artery is the preferred site to assess the condition of the patient’s arterial walls. The hardness and tortuosity of the arterial wall can best be assessed at this site. Heart rate and rhythm are usually assessed by palpating the brachial or radial pulse.
Palpation of the carotid artery usually detects a smooth, fairly rapid outward movement, beginning shortly after the first heart sound and the apical cardiac impulse. The pulse peaks at a third of the way through systole.
This peak is held momentarily and is followed by a downward run that is somewhat less rapid than the upward run. Variations in this pattern can be observed during the up, summit, or downward run.
The examiner’s timing of carotid pulse events can be improved by simultaneous auscultation of the heart. Palpation of the carotid pulse after a premature beat can be very helpful because certain pulse abnormalities are accentuated after a premature contraction.
taking your carotid pulse
The carotid arteries carry oxygenated blood from the heart to the brain. The carotid pulse can be felt on either side of the front of the neck just below the angle of the jaw. This rhythmic “beat” is caused by the variation in the volumes of blood leaving the heart to the extremities.
The pulse is usually felt just inside the wrist below the thumb by placing two or three fingers lightly on the radial artery.
Although there is a widespread prejudice against the use of the thumbs to assess pulses, the thumbs are useful for palpating large arteries.
Press just inside the medial border of a well relaxed sternomastoid muscle, approximately at the level of the cricoid cartilage. Avoid pressing on the carotid sinus, which is at the level of the top of the thyroid cartilage.
For the left carotid artery, use your fingers or right thumb. Never press both carotids at the same time. This can decrease blood flow to the brain and induce syncope.
The pressure should be light; If the artery is pressed too hard, the pulse will disappear completely.
Slowly increase the pressure until you feel a maximum pulsation, then slowly decrease the pressure until you feel your blood pressure and contour better.
The number of beats you feel in exactly 1 minute is the pulse rate. When you feel your pulse, look at your watch and count the number of beats in 10 seconds. Multiply this number by 6 to get your heart rate per minute.
The arterial pulse reflects the interaction between a driving force and the impedance of blood flow. The driving force depends on the intrinsic contractility of the left ventricle, the size and shape of the heart, and the heart rate.
Impedance is primarily related to peripheral resistance and arterial compliance associated with vessel wall compliance.
The arterial pulse wave begins with the opening of the aortic valve and the ejection of blood from the left ventricle. The pressure pulse increases sharply as blood enters the aorta faster than it flows to the periphery.
The left ventricle expels most of its stroke volume fairly quickly. A significant part of this rapidly expelled volume is temporarily held in the proximal aorta and other large central arteries that are normally quite compliant.
This rapidly increasing portion of the carotid pressure curve is called an anachronistic limb (anachrotic from the Greek for “optimistic”).
The height of the pulse pressure is approximately proportional to the relationship between stroke volume and arterial compliance. Arterial compliance, however, decreases as distended pressure within the artery increases.
Consequently, a given stroke volume will produce a higher pulse pressure if the mean arterial pressure is elevated. Arterial compliance is also inversely related to the rate of increase in intraluminal pressure.
As the ventricular ejection velocity accelerates, the arterial wall stiffens and the pulse pressure increases. The amplitude of the pulse pressure can also be modified by “peripheral runoff.”
Accelerated drainage will lower the diastolic pressure and result in a greater amplitude of the pulse pressure.
While the upward stroke of the carotid pulse reflects motive force and vessel compliance, the downward stroke reflects vessel compliance and peripheral resistance.
After the aortic pressure curve peaks, a decline begins as ventricular ejection slows and blood continues to flow to the periphery.
During the initial phase of ventricular relaxation, there is a momentary reversal of blood flow from the compliant central arteries to the ventricle. With this reversal of flow, the aortic valves close.
A notch at the descending extremity of the aortic pressure curve is associated with this transient reversal of blood flow. The subsequent smaller secondary positive wave, or dicrotic peak (dicrotic from the Greek “double beat”), has been attributed to elastic recoil of the aorta and aortic valve.
After this small wave, aortic pressure decreases as peripheral drainage continues.
An unequal pulse width in the two carotid arteries usually reflects atherosclerosis.
Other possible explanations include aortic dissection, arteritis, or embolus. A narrowing of the carotid artery is occasionally seen in a hypertensive patient and can mimic an aneurysm.
The hyperkinetic pulse is characterized by an increase in upward stroke speed and amplitude. The hammer in water, or Corrigan’s pulse, is characterized by a very strong upward stroke, great amplitude, and rapid collapse; it is an extreme form of the hyperkinetic pulse.
Hyperkinetic pulses can be associated with anxiety, exercise, fever, thyrotoxicosis, hypertension, aortic regurgitation, arteriovenous fistula, and patent ductus arteriosus.
Patients with marked bradycardia can compensate with a large, clinically apparent stroke volume manifested by a hyperkinetic pulse. The water hammer pulse is generally associated with aortic regurgitation.
The arterial pulse pulsus bisferiens (see Latin, “beating twice”), or bifid, is perceived as two closely spaced positive waves during systole.
The bifid pulse often occurs in patients with aortic regurgitation and is common in patients with combined aortic stenosis and aortic regurgitation.
A similar pattern can occasionally be seen in other conditions characterized by a hyperkinetic pulse. The bifid pulse is characteristic of idiopathic hypertrophic subaortic stenosis.
Hypokinetic arterial pulse is found in patients with reduced stroke volume. This group includes patients with hypovolemia, left ventricular failure, and mitral stenosis.
A small and delayed arterial pulse, parvo and delayed pulse, is characteristic of severe valvular aortic stenosis. However, it must be recognized that the absence of this finding, particularly in an elderly patient with a nonconforming vasculature, does not exclude severe aortic stenosis.
The paradoxical pulse is a characteristic pulse pattern in which there is marked attention to pulse width during the inspiratory phase of habitual respiration.
A paradoxical pulse must be measured with the sphygmomanometer and must be greater than 10 mm Hg to be significant.
Paradoxical pulse is common in pericardial tamponade, but can also be seen with asthma, chronic obstructive airway disease, and superior vena cava obstruction.
Pulsus alternans is a beat-to-beat variation in the amplitude of the pressure pulse. It can be accentuated after a premature contraction.
This pulse abnormality is usually best seen in distal arteries that have a wider pulse pressure than the carotid artery. Alternating pulse is a manifestation of severe depression in left ventricular systolic function.
Arterial pulse and pressure wave abnormalities
Pulse width correlates reasonably well with pulse pressure.
The contour of the pulse wave, that is, the speed of the upward run, the duration of its summit, and the speed of the downward run. The normal upward stroke is energetic.
It’s smooth, fast, and follows S1 almost immediately. The top is smooth, rounded and approximately mid-systolic. The downward race is less steep than the upward race.
Any variation in amplitude, either from beat to beat or with respiration.
Emotions and murmurs, during palpation of the carotid artery, you can detect buzzing vibrations, or emotions, that feel like the throat of a purring cat.
A carotid murmur with or without emotion in a middle-aged or older person suggests but does not prove arterial narrowing. An aortic murmur can radiate into the carotid artery and sound like a murmur.
Routinely, but especially in the presence of an emotion, you should listen to both carotid arteries with the diaphragm of your stethoscope for a murmur, a murmur-like sound of vascular rather than cardiac origin.
You should also listen for murmurs over the carotid arteries if the patient is middle-aged or elderly or if you suspect cerebrovascular disease. Ask the patient to hold their breath for a moment so that the sounds of the breath do not obscure the vascular sound. Heart sounds alone do not constitute a murmur.
Carotid artery conditions
Carotid artery vasculitis : inflammation of the carotid artery due to an autoimmune disease or infection.
Stroke – A sudden blood clot in the carotid artery can interrupt blood flow to the brain, causing a stroke. Fragments of cholesterol plaque in the carotid artery can also travel to the brain to cause a stroke.
Carotid artery stenosis : narrowing of the carotid artery, usually due to buildup of cholesterol plaque or atherosclerosis. Carotid artery stenosis usually doesn’t cause symptoms until it becomes severe.
Carotid artery aneurysm : A weak area of the carotid artery allows part of the artery to bulge out with each heartbeat. Aneurysms pose a risk of rupture, which could lead to a stroke or serious bleeding.
Carotid artery embolism : A piece of cholesterol plaque, or embolus, can break away from the wall of the carotid artery and travel to the brain, causing a stroke.
Carotid artery atherosclerosis : Cholesterol plaque can slowly build up on the wall of the carotid artery over decades. The growing plaque can eventually narrow the carotid artery, known as stenosis, and can lead to a stroke.
Amaurosis fugax : temporary blindness in one eye, usually caused by a fragment of cholesterol plaque, or embolus, that breaks away from the wall of the carotid artery. The embolus can get caught in an artery supplying the eye, blocking blood flow.
Temporal arteritis : an autoimmune disease in which the branches of the carotid artery become inflamed, known as vasculitis. Fever, a severe headache on one side of the head, and pain in the jaw when chewing can be symptoms.
Carotid hypersensitivity syndrome : In some people, applying pressure to the carotid sinus can cause fainting from a sudden drop in blood pressure. Symptoms can occur when shaving or wearing a tight shirt collar.
The brachial artery
The carotid arteries reflect aortic pulsations more accurately, but in patients with carotid obstruction, sprains, or chills, they are not adequate. If so, assess the pulse in the brachial artery, applying the techniques to determine amplitude and contour.
Your hand under the patient’s elbow and feel the pulse just medial to the biceps tendon. The patient’s arm should rest with the elbow extended, palm up. With your free hand, you may need to flex your elbow to a greater or lesser degree for optimal muscle relaxation.