The one 'reading' which almost any patient can take of his own heart is the pulse-rate. We do not encourage our patients to become introspective, but if, for any reason, the individual has been made aware of what appears to be a too-fast or too-slow pulse, the following brief notes may lead to a better understanding.
Perhaps the first point to clear up is a common error about the pulse as heard by the patient, when in very quiet surroundings: typically, lying in bed at night, with a growing awareness of a very 'busy' pulse throbbing within the head. The normal pulse has two peaks per cycle, of which the first is by far the greater and is the true heart beat. The second is comparatively minor and is produced by what one may call an 'echo' of the original pulse within the large blood-vessel.
However, in the right circumstances, the sound heard from this second little throb appears to be just as loud as the first, and the already anxious patient may easily imagine his pulse-rate to be doubled.
Were he more observant, and less concerned, he would notice that this 'terribly fast pulse' consists not of evenly spaced and identical sounds, but of pairs of sounds, with alternating short and long intervals. Were he then to take his pulse in a more professional way, by laying the finger-tips of one hand upon the thumb side of the other wrist, he would instantly recognize his error: only the first noise of each pair correspond s with the real pulse.
Cardio & Blood