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Arterial Pulse

Arterial pulse is defined as the pressure changes transmitted in the form of waves through arterial wall and blood column from the heart to the periphery.

When heart contracts, the blood is ejected into aorta with great force. It causes distension of this blood vessel and a rise in pressure. A pressure wave is produced on the elastic wall of the aorta. It travels rapidly from the heart and can be felt after a brief interval, at any superficial peripheral artery like radial artery at wrist. 

Pulse rate is the accurate measure of heart rate, except in conditions like pulses deficit (see below).

„ TRANSMISSION OF PULSE

Central arterial pulse is transmitted to the peripheral arteries as peripheral arterial pulse. Formation and transmission of pulse wave depends upon the elasticity of blood vessels. Thus, when the walls of the arteries are more distensible, the pressure rise is less and so the transmission of pulse is less. When the arterial wall loses its elastic property and becomes rigid as in old age, the pressure rise is more and the transmission of pulse is also more.

Pulse is not transmitted to capillaries because capillaries are devoid of elastic tissues. 

„ VELOCITY OF TRANSMISSION OF PULSE

Average velocity at which the pulse wave is transmitted varies between 7 and 9 meters/second. Pulse travels faster than the blood. Maximum velocity of blood flow in the body (in larger arteries) is only 50 cm/second.

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„ DELAY IN TRANSMISSION OF PULSE

At the arteries, pulse is felt after a short interval from the beginning of ventricular systole. This delay is very small and it can be measured only by accurate recording. The delay is directly proportional to the distance from heart.

Delay of pulse at:

1. Common carotid artery: 0.01 to 0.02 second

2. Radial artery: About 0.08 seconds.

„ METHODS OF RECORDING ARTERIAL PULSE

„ BY MANOMETER 

In animals, pulse is recorded by inserting a cannula into the dissected artery. This cannula is connected to a manometer or any recording device.

„ BY DUDGEON SPHYGMOGRAPH

Dudgeon sphygmograph is tied to the wrist in such a way that, a small plate rests on the skin over radial artery. Movements of arterial wall are magnified by a series of levers and are recorded on a moving strip of smoked paper. This instrument is outdated and it is replaced by electronic pulse transducers.

„ BY ELECTRONIC PULSE TRANSDUCER

Pulse transducer is placed over the finger and tied. This device throws light on the blood vessel through skin. Sensor of the transducer detects the light rays reflected from the flowing blood. Alteration in frequency of the reflected light rays is amplified and recorded by connecting the transducer to a recording device like polygraph. The record shows finger pulse volume, which represents the arterial pulse tracing.

„ INTERPRETATION OF ARTERIAL PULSE TRACING

Pulse recorded in radial artery or femoral artery is the typical peripheral pulse. Peripheral pulse tracing has three main features:

1. Anacrotic Limb

Anacrotic limb or primary wave is the ascending limb or upstroke. It is due to the rise in pressure during systole.

2. Catacrotic Limb

Catacrotic limb is the descending limb or downstroke. It is due to the fall in pressure during diastole.

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3. Catacrotic Notch 

In the upper part of the catacrotic limb of pulse tracing, a small notch appears. It is known as catacrotic notch or incisura. This notch is produced by the backflow of blood during the closure of semilunar valves at the beginning of diastolic period, which produces slight increase in the pressure.

4. Precatacrotic and Postcatacrotic Waves 

The wave appearing before the catacrotic notch is called precatacrotic wave. The wave appearing after the notch is called postcatacrotic wave.

„ PULSE POINTS

Usually, pulse is palpated on the radial artery because it is easily approachable and placed superficially. However, arterial pulse can be felt in different areas on the body. These areas are called pulse points

Pulse point Area of palpation

 1. Temporal pulse Over the temple, in front of ear on superficial temporal artery

 2. Facial pulse On facial artery at the angle of jaw

 3. Carotid pulse In the neck along anterior border of sternocleidomastoid muscle on common carotid artery

 4. Axillary pulse In axilla on axillary artery

 5. Brachial pulse In cubital fossa along medial border of biceps muscle on brachial artery

 6. Radial pulse Over the thumb side of wrist between tendons of brachioradialis and flexor carpi radialis muscles on radial artery

 7. Ulnar pulse Over the little finger side of wrist on ulnar artery

 8. Femoral pulse In the groin on femoral artery

 9. Popliteal pulse Behind knee, in the popliteal fossa on popliteal artery

10. Dorsalis pedis pulse Over the dorsum of foot on dorsalis pedis artery

11. Tibial pulse Over the back of the ankle, behind medial malleolus on posterior tibial artery

„ EXAMINATION OF RADIAL PULSE

Examination of pulse is a valuable clinical procedure. Pulse represents the heartbeat. By examining pulse, important information regarding cardiac function such as rate of contraction, rhythmicity, etc. can be obtained. 

In addition, an experienced physician can determine the mean arterial pressure by hardness of pulse and its amplitude.

Method of Examining Radial Pulse

Subject is made to sit comfortably with forearm placed in mid or semi-prone position, with wrist slightly flexed. The observer must stand by the right side of the subject. Tips of the middle three fingers (index finger, middle finger and ring finger) are placed over the radial artery below the wrist at the base of thumb. Light pressure is applied by the fingers until the pulse is felt. If necessary, the fingers are moved around till the pulse is felt. Index finger is used to occlude blood flow from radial artery. Ring finger is used to occlude retrograde flow of blood from ulnar artery through palmar arch. Middle finger is used to assess the pulse. 

Observations during Examination of Pulse

1. Rate

2. Rhythm

3. Character

4. Volume

5. Condition of blood vessel wall

6. Delayed pulse.

„ 1. RATE

Pulse rate is the number of pulse per minute. It has to be counted at least for 30 seconds. Pulse rate in adults is 72/minute. 

Pulse Rate at Different Age

In fetus: 150 to 180/minute

At birth: 130 to 140/minute

At 10 years of age: 90/minute

After puberty: 72/minute.

Variations

Conditions that alter the heart rate alter pulse rate also. 

Pulse rate increases during:

 i. Exercise

 ii. Pregnancy

 iii. Emotional conditions

iv. Fever

v. Anemia

 vi. Hypersecretion of catecholamines

 vii. Hyperthyroidism. 

Pulse rate decreases during:

 i. Sleep

 ii. Hypothermia

 iii. Hypothyroidism 

iv. Incomplete heart block.

„ 2. RHYTHM

Rhythm is the regularity of pulse. It refers to interval between beats. Under normal conditions, the pulse appears at regular intervals. Rhythm of the pulse becomes irregular in conditions like atrial fibrillation, extrasystole and other types of arrhythmia.

Pulse with irregular rhythm is of two types: 

i. Regularly irregular pulse 

ii. Irregularly irregular pulse. 

„ 3. CHARACTER

Character denotes the tension on the vessel wall produced by the waves of pulse. It is usually evaluated at right carotid artery. Normally, it is not possible to detect the different waves of the pulse or slight variations in the character or form of the pulse. However, it becomes more prominent in some abnormal conditions such as anacrotic pulse, water hammer pulse, pulsus paradoxus, etc. which are explained later in this chapter.

„ 4. VOLUME

Volume is the determination of movement of the vessel wall, produced by the transmission of pulse wave. It is also a measure of pulse pressure. It depends upon the condition of the blood vessel.

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„ 5. CONDITION OF THE BLOOD VESSEL WALL

Condition of wall of the blood vessel is assessed by feeling the radial artery and rolling it against the underlying bones. Normally, the wall of the vessel is not palpable in children and young adults. However, in old age the wall of the vessel becomes rigid and palpable. In abnormal conditions like arteriosclerosis, it is felt as a hard rope.

„ 6. DELAYED PULSE 

Sometimes, the arrival of pulse in certain peripheral arteries is delayed. It is an important feature to be noted because it is useful in diagnosis of certain diseases. 

Types of delayed pulse: 

i. Femoral delay

ii. Radial-radial delay.

i. Femoral Delay 

While palpating radial pulse and femoral pulse simultaneously, there is a short delay in the arrival of femoral pulse wave. Normally, it is negligible and unnoticed. However, the prolonged or noticeable delay in the arrival of femoral pulse indicates coarctation (narrowing) of aorta. This delay is called femoral delay, radial femoral delay or radio femoral delay.

ii. Radial-radial Delay 

When both the radial pulses are examined simultaneously, sometimes the arrival of pulse is delayed on one side. It is called radio-radial delay or radial-radial delay or radial-radial inequality. This indicates the narrowing of large artery due to atherosclerosis.

„ APPLIED PHYSIOLOGY – ABNORMAL PULSE

„ 1. PULSUS DEFICIT 

Pulsus deficit is the abnormal condition in which the pulse rate is less than the heart rate. It occurs in atrial fibrillation when the stroke volume is reduced. Because of reduced stroke volume, some of the pulse waves become weak and disappear before reaching the peripheral arteries. Pulsus deficit is the only condition in which pulse rate is less than the heart rate.

„ 2. PULSUS ALTERNANS

Pulsus alternans is the abnormal condition in which the amplitude of every second wave in pulse tracing is relatively smaller. It is because of the alternate variation in the force of ventricular contraction. However, the rhythm of the pulse is not altered. It is common in severe myocardial diseases, paroxysmal tachycardia and atrial fibrillation. 

„ 3. ANACROTIC PULSE 

Anacrotic pulse is the abnormal pulse, characterized by a slow ascending limb which has a notch called anacrotic notch. It is produced in aortic stenosis when ejection is slow.

„ 4. THREADY PULSE OR WEAK PULSE

Thready or weak pulse is the abnormal pulse in which the volume of pulse becomes very feeble and is hardly felt at the arteries. It usually occurs whenever the stroke volume decreases or when there is severe vasoconstriction, as in the case of severe haemorrhage or severe chills. In these conditions, the sympathetic activity increases enormously, leading to generalized vasoconstriction. 

„ 5. PULSUS PARADOXUS

Pulsus paradoxus is the condition when the pulse becomes very strong and very weak alternately, in relation to respiratory cycle. Normally, there is a slight increase in volume of pulse during inspiration and slight decrease in volume during expiration. But, it is hardly noticed. However, when it becomes very prominent, it is pathological. This type of pulse is noticed in cardiac tamponade. It is also noticed in physiological conditions such as deep breathing.

„ 6. WATER HAMMER PULSE

Water hammer pulse is the abnormal pulse, characterized by a rapid upstroke and an equally rapid downstroke. It is also called collapsing or Corrigan pulse. It is seen in conditions like aortic regurgitation, patent ductus arteriosus and arteriovenous fistula. It is best felt by raising the arm of the subject and holding it by grasping the wrist with palm of the observer. 

„ 7. ABNORMAL PULSE IN PATENT DUCTUS ARTERIOSUS

Patent ductus arteriosus is the permanent existence of ductus arteriosus. In fetus, the lungs are nonfunctioning. So, the blood which is pumped by right ventricle into the pulmonary artery, is diverted to systemic aorta through ductus arteriosus. Ductus arteriosus closes after birth. However, in some cases, it exists without closing.

Pulse pressure wave is very much altered in this condition. Since, the blood flows from systemic aorta arteriosus and aortic regurgitation to pulmonary artery, after every ventricular systole, the blood flows out of aorta quickly. It decreases the diastolic pressure and the catacrotic limb of the pulse tracing falls below the level of 80 mm Hg.

Flow of blood from aorta to pulmonary artery increases the venous return to left side of the heart. So, left ventricular output increases, which in turn elevates the systolic pressure in arteries. Thus, in pulse tracing, the peak of the pulse wave is elevated above the level of 120 mm Hg. So, the pulse tracing in this condition reveals the increased pulse pressure.

„ 8. ABNORMAL PULSE IN AORTIC REGURGITATION

Aortic regurgitation is the backflow of blood from aorta into left ventricle. It is common during incompetence of semilunar valve in aorta. It decreases the diastolic pressure. Because of backflow of blood, the left ventricular filling increases greatly, leading to increase in output and systolic pressure. Thus, the pulse tracing in aortic regurgitation is more or less similar to that in patent ductus arteriosus. Only difference is that in the tracing during aortic regurgitation, the incisura is very mild. And in severe conditions, when the aortic valve does not close, the incisura is absent.