pulse

pulse Feeling the pulse is one of the hallmarks of the medical profession, and has been for many a century. As well as being informative, this action can give the doctor something physical to do while he takes time to think.

The pulse is most commonly felt where the radial artery lies near the surface on the thumb side of the wrist. It is made palpable by the ‘pulse pressure wave’ — initiated by each heart beat — reaching and expanding the artery. This wave is transmitted to the wrist at about 10 metres per second around forty times faster than the speed of the blood flow itself.

The information obtained from feeling the pulse is limited but important. The feel of the artery itself may suggest whether its wall has normal resilience, or is hardened and thickened by arteriosclerosis.

The pulse may feel, at one extreme, ‘strong’ and ‘full’ or, at the other, ‘weak’ or ‘thready’. These are indirect indications of the stroke volume of the heart. The impulse felt in the radial artery is related to the rise in arterial blood pressure generated by the heart at each beat — the pulse pressure. For any given stroke volume, this rise in pressure depends on the elasticity of the arteries: the more compliant they are the less the pressure rises; the stiffer they are with age and arteriosclerosis, the more sharply the pressure rises. These subtleties may be recognized by an experienced observer.

The rate may be faster or slower than normally expected in the circumstances. In healthy adults the rate at rest, although typically 60–70, can be anything from 40 per minute, say in an elite long-distance swimmer, to about 80 per minute. Even so the rate can, for example, be used to distinguish a simple faint (slow) from loss of consciousness caused by haemorrhage (fast).

The rhythm may be regular or irregular. In a person at rest an absolutely regular pulse is in fact unusual because of the phenomenon of respiratory sinus arrhythmia — an increase when breathing in and a decrease when breathing out. This is more marked in younger than in older people, and disappears at higher heart rates such as in exercise or in fever. This is a ‘regular irregularity’ and the pattern is generated from the normal physiological pacemaker, the sino–atrial node. There are other, abnormal disturbances of rhythm which are ‘irregular irregularities’; in this instance the rhythm is occasionally interrupted or persistently disorganized. Interruptions can either come in the form of extra heart beats, generated from a different part of the heart rather than from the sino–atrial node (ectopic beats), or else an occasional beat may be missed out entirely in mild forms of heart block. ‘My heart missed a beat’ is not just poetic licence: the sensation of missing a beat, in healthy people, is usually because of a longer gap after a premature ectopic beat. A totally disorganized rhythm is felt at the pulse in the condition of atrial fibrillation.

An exaggerated sensation of the beating of the heart — palpitation — may or may not be associated with a faster than normal pulse rate; it is also a normal accompaniment of the increase in strength and rate of the heart-beat induced by strenuous exercise, or by the sympathetic nervous systems in stressful conditions, and can be a component of abnormal anxiety states.

Awareness of pulsation within ourselves, particularly when emotions are heightened — and even at the earliest in our mother's womb — may well be inextricably related to the creation and appreciation of music.

Sheila Jennett

See also heart; medicine; music; pacemaker.