THE PULSE

The pulse is iconic and defines the identity of the physician from others since time immemorial even before the stethoscope was in vogue. Examination of the pulse involved pulsation of a nearly constant peripheral artery. The artery is fixed in position and accessible easily. Usually, the artery is superficial and lies in a bony grove ensuring palpable reproducibility. The ability to deduce from the palpable pulse is unique and differentiates a good clinician from the rest.

Palpation of the pulse is a special art. This was considered an extremely important part of clinical diagnosis. Since antiquity, the pulp of two or three fingers was used to locate, feel the character, and determine the direction of the pulse.

In ancient China (280 BC), Wang Shu-he wrote 10 books about the pulse. The Greeks called the pulse “sphygmos”, and sphygmology thus deals with the theory of pulse. Galen, in Roman times, interpreted the various types of pulses according to the that each organ in each disease has its form of a pulse.

In traditional Indian medical practice, the appreciation of the ‘nari’ with the recognition of ' bayu’, ‘pitta’, and ‘kof' is somewhat related to the three senses of humor in developing medicine of the civilized population. The experienced physicians of the so-called ‘pagan’ medical practice were capable of not only pinpointing diagnosis but also predicting the time of death (‘nidan’).

It is said that Herophilus, a pre-Galenian clinician, understood the importance of the pulse and was responsible for its introduction to clinicians as a diagnostic tool. Later even a 'pulse watch' was devised where the 'second' hand could be stopped at the desired time.

One important clinical use of peripheral and central pulses occurs during cardiopulmonary resuscitation (CPR) when the pulse is used to know whether the individual is alive and estimate the patient’s systolic blood pressure quickly. Palpable pulses in various locations probably relate to systolic BP, and the belief is that they are only palpable above certain systolic BP thresholds, with bigger and more central vessels having lower thresholds. One previous estimation was that the radial pulse is no longer palpable below 80 systolic BP, the femoral unpalpable below 70, and the carotid unpalpable below 60.

In the upper extremities, the two peripheral pulses are the radial and brachial. Examiners frequently evaluate the radial artery during a routine examination of adults, due to its easy accessibility and even palpate it without proper exposure. Palpation is at the anterior wrist just proximal to the base of the thumb. The brachial artery is often the site of evaluation during cardiopulmonary resuscitation of infants and children. It is palpated proximal to the elbow between the medial epicondyle of the humerus and the distal biceps tendon. The carotid is the preferred pulse point used during the resuscitation of adults.

In the lower extremities, the commonly evaluated pulses are the femoral, posterior tibial, dorsalis pedis, and sometimes the popliteal. The femoral pulse may be the most sensitive in assessing for septic shock and is routinely checked during resuscitation. It is palpated distally to the inguinal ligament at a point less than halfway from the pubis to the anterior superior iliac spine. The posterior tibial pulse may be the most difficult to palpate, especially among less experienced clinicians. It is located immediately posterior to the medial malleolus. The dorsalis pedis is at the anterior aspect of the foot, lateral to the extensor hallucis tendon, and is generally within 1cm of the bony prominence of the navicular bone. Therefore, asking the patient to extend their first toe can help elevate this landmark and may make the pulse easier to identify. However, it may be absent due to an anatomical variation in 10% of the general population. Finally, the popliteal pulse is present in the popliteal fossa slightly lateral of the midline.

The pulse is appreciated by its volume or the amplitude of circumferential distensibility. A distinctly palpable pulse indicates good volume. Any superficial vessel can be palpated for an arterial waveform. The larger arteries like the carotids or the brachial, of either side. are often palpated for a better appreciation of the nature of the pulse. The choice of where to palpate a peripheral pulse depends on factors including the patient’s age, body habitus, and clinical situation.

The choice of where to palpate a peripheral pulse depends on factors including the patient’s age, body habitus, and clinical situation. It is relevant to compare bilateral pulses for symmetry as well as the difference between upper and lower extremity pulses.

This clinically helps diagnose conditions like co-arctation long before invasive investigations are used.

It should be realized that the pulse wave is usually single and variations within it are seen. Evaluation begins with whether the pulse is bounding or weak, fast or slow, irregular or regular, and equal or unequal bilaterally. The intensity of the pulse is noted and subjectively graded on a scale of 0 to 4. By convention, “plus” always follows the number (e.g., 1+). Zero refers to a nonpalpable pulse, 1+ is a barely detectable pulse, 2+ is slightly diminished but greater than 1+, 3+ is a regular pulse and should be easily palpable, and 4+ is “bounding” (e.g., stronger than normal). Conventionally 15 seconds multiplied by 4 is the time taken to evaluate a pulse. The radial pulse is the physician's choice and the recommendation is not less than a minute.

Usual practice during clinical examination is a non-invasive examination of the peripheral radial pulse and its interpretation. The following points are to be remembered:

1. Pulse in the peripheries are not palpable in circulatory shock and here, when faintly noticeable, often a respiratory variation with a rapid pulse can be appreciated. in situations where the heart is not allowed to beat to its potential, viz., constrictive pericarditis. This is the pulsus paradoxus of the past. Nowadays, it is better called a pulsus normalis exaggeratus as it is understood that there is nothing paradoxical about the pulse here.

2. A slow rise to its peak with a low volume is called a pulsus parvus and if the rate is slow, it is best known as pulsus parvus et tardus. This is also referred to as an anacrotic pulse.

3. There are many forms of a hyperkinetic pulse. In circulatory shock states, anaemia, and hypovolemia, the pulse is rapid and of a low volume.

4. Sensitive individuals can appreciate the 1st peaking of a larger amplitude before the 2nd lesser peaking in a dicrotic pulse.

5. Aortic pathology is almost always associated with a biphasic pulse. Two distinct pulse peaks can be felt, the 2nd one, usually, has a larger amplitude.

6. The bisferience pulse is an extreme form of hyperkinetic pulse where double peaking is a distinctive feature, and the 2nd peak of pulsatile feel is due to a venturi effect of the retuning blood after a sudden collapse. Supra-aortic stenosis may exhibit a similar pulse.

7. In hypertrophic obstructive cardiomyopathies, the BH pulse is ‘jerky'. The same may be found in sub-aortic stenosis.

8. Rhythm disturbances are associated with a variety depending upon the pumping ability of the heart. A bigeminal pulse, best known as the pulsus alternance is appreciated in two close QRS complexes followed by a compensatory pause.

9. Drop beats in the pulse are appreciated in conditions where there is an interruption of the heartbeat.

10. A slight pressure elicits an alternate blanching and darkening of the nails and nail bed in aortic regurgitation. This is known as Quincke’s pulse and is a combination of observation and palpatory methods.

11. A clear volume difference can be appreciated between the upper and lower limbs in the coarctation of the aorta, both pre- and post-ductal.

For monitoring and analysis, invasive cannulation of a peripheral artery, commonly radial, is required. A complex waveform that consists of a simple ascending wave, a peak, and a sloping descending wave interrupted with a notch representing the systolic ejection of blood by the heart, its diastolic relaxation, and the distensibility of the vessels carrying this blood. So, the pulse wave we see in the monitor comprises a -->

systolic upstroke, systolic peak pressure,

systolic decline, dicrotic notch,

diastolic runoff.

The notches in the waves represent the pliability of the artery carrying the blood. Ascending limb notches appear rarely and are called anacrotic notches. Dicrotic notches in the descending limb or the dicrotic peak are more constant and correspond with the tri-leaflet aortic valve closure by the diastolic reflected wave. There is a dramatic increase in arterial resistance at the arteriolar level. There will be variations in the arterial waveform in diseases and notches in the upstream (anacrotic notches) may be seen with aging leading to stiff arteries and pulmonary hypertensive situations or right ventricular dysfunctions.

As visualized on a monitor.

After the ascending systolic upstroke, the waveform tends to round off with a peak. This is the peak systolic pressure, and it is a reflected wave dependent on both arterial wall stiffness and the backward shockwave once the column of blood reaches the poorly compliant arterioles. There may be an anacrotic notch before the reflection of the upstroke of the systolic peak. The systolic decline is rapid indicating termination of forceful systolic contraction and commencement of diastolic relaxation of the heart. The semi-lunar aortic valve closure happens around the period of the dicrotic notch. An incisura can be there indicating aortic valve closure, and the end of systole as indicated by the dicrotic notch. The 2nd smaller peak follows and then the diastolic runoff continues till the end of a cardiac cycle. As the waveform progresses into the narrower peripheral arteries, the waveform changes and a narrower and higher amplitude wave is produced. Larger diameter arteries with compliant walls may show the region where the actual systole ends by a notch in the ascending limb, but with a progression of the blood column, the notches disappear.

Of the peripheral arteries, the radial artery appears most suitable because of its optimum dimensions, more or less fixed position in a bony groove in the wrist region, and convenient accessibility. The position of the 2nd peak of the dicrotic notch also shifts progressively further away from the peak of the arterial wave due to a larger distance having to be covered by a shock wave produced by the closure of the aortic valve.

In this diagram, the pink area under the pulse wave contour is the systole period and is representative of the stroke volume. The blue area is the diastolic phase. If the pulse waveform is gated with the ECG, then the -----

STROKE VOLUME X HEART RATE = CARDIAC OUTPUT.

This is a rough idea in crunch situations and gives an idea of the health of the heart. A detailed, continuous, and accurate value of the cardiac output is available in the present-day automated monitors the thermodilution techniques.

A reference to the mean arterial pressure (MAP) needs a mention here. The easiest way of measuring it is by the formula ---

(SYSTOLIC + 2 X DIASTOLIC) / 3 or MAP = DIASTOLIC PRESSURE + 1/3 PULSE PRESSURE.

In emergent conditions, the physician always tries to shore up the MAP to values above 60 mm of Hg. A MAP value between 60 to 110 mm of Hg is necessary for perfusing the end organs adequately. The simple non-invasive method is capable, but the invasive arterial cannulation-based techniques are better. Continuous monitoring devices always give the value of MAP even if the systolic and diastolic pressures are not mentioned. There are certain factors for individual age groups for increased heart rates and uneven pulse waveforms due to variations in the cardiac output for determining MAP using a formula where the diastolic blood pressure and the pulse pressure are required. An accurate MAP may be calculated from the whole area under the pulse curve, systemic vascular resistance, and central venous pressure using thermodilution techniques and continuous cardiac output monitors this. In modern times, clinicians are going to find a few patients with implanted assist devices and non-invasive pressure monitoring them for follow-up is not possible. The only way is arterial cannulation and invasive mean arterial pressure monitoring. As this is cumbersome, bedside echocardiography has become the alternative along with a detailed physical examination and functional evaluation of the patient.

Traditionally, the screening tool for PAD is the ankle-brachial index (ABI), which compares the systolic blood pressure in the ankle to that in the arm. This test is somewhat time-consuming and requires specific equipment and training. New luminographic radiological studies give one a better visual impression of the location of lesions once such a lesion is suspected. However, it is important to realize the concept of an ankle-brachial index. The distal pressure is always higher (in erect posture) or equal, 1 is considered the normal value, any value below 1 tells the evaluating team that proportionally a lesser per cent of blood is flowing to arteries beyond, and an index of 1.4 is indicative of a higher hydrostatic pressure with a consequential high systolic blood pressure and stiff vessels. Proper recording of the ankle-brachial index consists of a qualitative portion (where an audible part is there) or an analog part, as shown below:

The interpretation of the ankle-brachial index in a simplified manner is as follows:

The vascular pulse in the arteries synchronizes with the heart contractions. Commonly the radial pulse in the wrist region is felt for the upper limbs in a conscious subject. The brachial pulse in the cubital fossa is sought whenever there is doubt about the radial pulse. The carotids are felt basically when there are inequalities on the two sides of the body, investigate reasons for unconsciousness, confirm life, etc. The femoral, popliteal, dorsalis paedis, and posterior tibial from above downwards are the common sites for pulse palpation in the lower limbs. The sites are mostly constant and against fixed anatomical landmarks. When distant peripheral pulses are felt and the extremities are turgid and well perfused, one can confidently predict a blood pressure of 90+ systolic. Rate, rhythm, volume, and condition of the arterial wall are the four parameters commonly looked for when feeling for the pulse. The pulse count is a range and a large variation from 60 below to around 100 is considered normal. Being the direct representative of the systolic contraction of the heart, the pulse also is representative of the metabolic activity of the body. Any stressful situation will increase the heart rate. Anxiety also causes the heart to beat faster. When the rate is more than 100, the term tachycardia is used and alternatively, bradycardia is the clinical term for a pulse below 60. Fever, fear, and frenetic activity are common examples of tachycardia. Deep sleep and myxoedema where the metabolic activity is low are states where bradycardia is the rule. Pulsus alternance occurs when the ventricle is failing and there is a distinct variation in pulse volume in alternate beats. When feeling for the pulse, the first thought is about the count, then regularity and rhythm come. The rhythm can be regular, irregularly regular, and irregularly irregular depending upon the electrical activity of the heart. Various forms of heart block, atrial flutter, fibrillation, ectopics, etc., are the usual causes of irregular rhythms. Appreciation of the volume gives the examiner an idea of the prevailing blood pressure and the state of the patient. Appreciation of satisfactory pulse volume will not be possible if the pulse pressure, which is the difference between systolic and diastolic pressures, is low. Arteriosclerotic changes, vessel wall calcification, diabetes, chronic renal failure, and age cause some changes in the vessel wall that lead to a degree of stiffening where the pulse is not felt normally. An idea is necessary at this stage about arteriosclerosis and atherosclerosis. Both affect the arterial wall, and the latter involves a fatty and calcific deposition in the pronounced medial wall of arteries leading to a diminution of luminal diameter. This is a gradual process causing a loss of pliability with the lessening of blood flow. Arteriosclerosis is a generalized process of stiffening the arterial wall due to several conditions. Some of these are summarized as follows: • Non-atheromatous arteriosclerosis – this happens due to degenerative fibrosis in aging. • Monkeberg’s sclerosis – here the cause is a degenerative calcification of the vessel wall. The artery diameter, blood flow, and intravascular clot formation are not altered. • Hyaline arteriosclerosis – mainly the small arteries and arterioles are affected with protein deposition along the arterial wall in places. Diabetic arteriopathy is a classic example of weakening and narrowing of the small vessels jeopardizing blood flow. • Hyperplastic arteriosclerosis – this is said to happen in long-standing hypertensive individuals. Arterial wall irregularity, thickening due to protein deposition at places, and flow compromise are the usual features. • Atherosclerosis – this condition is studied the most as it preferentially affects large and medium-sized arteries like arteries of the heart. There is fatty plaque deposition in the arterial walls and these plaques grow in size with time, narrow or even block luminal diameter, ulcerate causing a perfect milieu for intravascular clot formation, embolism, etc. Remodeling of the vessel wall is a feature of long-standing hypertension --- this may be non-atheromatous or Monkeberg sclerosis as in aging, hyperplastic thickening of the wall as with long-standing hypertension, or atheromatous affection. Hypertensive arteries are prone to all sorts of pathological changes. The incidence of coronary ischemia is high and cerebrovascular accidents, be it thrombotic, embolic, or hemorrhagic, occur more frequently in the hypertensives. The pulse volume, in reality, depends on factors like: • Pliability and expansibility of the arterial wall with each systolic contraction of the heart, • A wide pulse pressure, • Proximity to the heart, • Size of the vessel. The volume can be good or adequate when the rise is felt briskly. The volume may have a slow rise and be poorly felt – pulsus parvus et tardus. However, when a pulse can be distinctly felt in a peripheral fixed location, the individual is conscious, and the periphery is warm then the contractility of the heart is adequate and the systolic blood pressure ≥90 mm of Hg. Aortic lesions and disturbances in the inherent conductive pathway of the heart bring out numerous pulse variations. Clinically they are even relevant today leading to a provisional diagnosis based on which further corroborative investigations and clinical tests are advised. In aortic stenosis, the volume is low and there is a slow rise – pulsus parvus et tardus. Dual splitting of the pulse is seen in aortic regurgitant lesions. This is also called pulsus bisferience. The Corrigan’s pulse is rapid, forceful, and quick leading to the ‘water hammer’ effect which is felt on the volar aspect of a hand and fingers encircling the wrist. The often-noticed signs of various degrees of aortic regurgitation are as follows: • De Musset’s sign: Bobbing of the head with each heartbeat (like a bird walking) • Muller’s sign: Visible pulsations of the uvula • Quincke’s sign: Capillary pulsations seen on light compression of the nail bed • Traube’s sign: Systolic and diastolic sounds heard over the femoral artery (“pistol shots”) • Duroziez’s sign: Gradual pressure over the femoral artery leads to a systolic and diastolic bruit • Hill’s sign: Popliteal systolic blood pressure exceeding brachial systolic blood pressure by ≥ 60 mmHg (most sensitive sign for aortic regurgitation) • Shelly’s sign: Pulsation of the cervix • Rosenbach’s sign: Hepatic pulsations • Becker’s sign: Visible pulsation of the retinal arterioles • Gerhardt’s sign (aka Sailer’s sign): Pulsation of the spleen in the presence of splenomegaly • Mayne’s sign: A decrease in diastolic blood pressure of 15 mmHg when the arm is held above the head (very non-specific) • Landolfi’s sign: Systolic contraction and diastolic dilation of the pupil. Conductive disturbances are evident when the regularity is lost, there are dropped beats and there are sudden and repetitive episodes of transient black-outs or unconsciousness (Stokes-Adam’s attack). There may be extreme symptomatic bradycardia, missed beats with recurrent reeling sensations, or blackouts indicating recurrent attacks of transient loss of consciousness and the representative pulse indicating a suggestion of conduction anomaly. In some cases, the pulse may be normal and further electrophysiological studies are needed to arrive at a diagnosis. Tachycardia or increased heart rate is associated with a low pulse volume as the rhythm is intricately related to the contractile activity of the heart. In such a situation, the diastolic time is unduly short not giving time for optimal myocardial stretching for generating adequate power. Extreme tachycardia may render a person pulse less. This happens in ventricular tachycardia, atrial flutter, and atrial fibrillation. In the latter two conditions, not all atrial waves travel down the Purkinje fibers and incite an effective ventricular contraction. Clinically in atrial flutter, the pulse is regular and fast. On the other hand in atrial fibrillation, though faster than normal, the pulse is always irregularly irregular and there is a difference between the number of times the heart beats and the pulse rate. This is known as the pulse deficit. Arrhythmia due to atrial fibrillation is the commonest of all post-surgical rate and rhythm anomalies the cardiac surgeon has to treat in his career as it can create prognostically bad hemodynamic instability. Comparison of the upper limb and lower limb pulses is a necessary clinical step. It helps not only in an assessment of the peripheral circulation but also in the diagnosis of coarctation of the aorta where there is a sudden lowering of volume in the lower limbs. The distal pulses may even be absent due to developed collaterals sustaining nutritional needs. In pre-ductal and pre-left subclavian coarctation the left upper limb may also be affected. A radio-radial delay in pulse palpation can also be found in other conditions like atherosclerosis, arteritis, dissection, and embolic stenoses. Pulse examination is still important and gives the initial clue whether anything is wrong. It has retained its talismanic position in the clinical evaluation of a subject. The common person cannot still imagine seeing a physician not feeling the pulse in the wrist region.