When a doctor takes a pulse he is feeling the patient’s heart-beat. If the heart is beating faster than normal it may be a sign like a rise in temperature of illness somewhere in the body. For signs of illness in the heart itself a more careful check is usually needed.
The working of the heart is controlled by electrical impulses, and each part of it the various valves where blood flows in a out produces its own electrical wave pattern. By attaching electrical terminal points to the outside of the chest and connecting these to an electrocardiograph, these wave patterns can be observed. For when the electrocardiograph is switched on, an automatic device like a pen moves up and down over a special sheet of graph paper, recording each wave impulse. This shows exactly the pattern of each complete heart beat. If anything is wrong with the heart, it will be shown by irregularities in these patterns. The patterns sheets, or electrocardiograms, can then be kept by doctors and compared over a period of time, which is extremely useful in the treatment of heart illness.