Irregular Heart Electrocardiography
( Originally Published 1921 )
THIS is the name given to the process by which a heart may be made to write its own autograph by recording the intrinsic electricity that is generated by the movement of the various parts. This process is the foundation of the modern treatment of heart disease. It is a pity that so simple a study as electrocardiography should have such a long and complicated name and that the study itself should have been obscured at times through the technical discussion of unimportant points.
The true nature of electrocardiography and its value is best illustrated by a simile: The heart is shut up in the chest and the problem is how to know or recognize the activities of its various parts. In the past we have been dependent upon indirect means of inference and observation by listening to the sounds of the heart or judging by the waves that are produced in the blood stream. Now we can procure a record of each motion of each part of the heart.
Suppose that a frog were shut up in a box and a group of wise men gathered around the box to decide what motions the frog was making with its limbs. By carefully listening to the sounds recorded by the walls of the box one might distinguish the kick of a hind leg from the scratching sound of the front leg. How-ever, it is more than probable that there would be some difference of opinion among the wise men as to the motion of the particular leg producing the sound. If to the legs of the frog strings of different color were attached and led outside of the box, it would be easy to decide which leg moved, as the particular colored string would transmit the impulse. If, later, on, it should be discovered that each muscle of the frog's legs as it contracted generated its own peculiar electric current, a pair of wires could be attached to the frog and by recording these currents we could ascertain just what motions the frog was making with each of its legs.
In electrocardiography the heart takes the place of the frog and the electric currents from the heart are easily collected by wires attached to the hands and feet of the person undergoing examination. This is all that a practitioner needs know of this method of recording the heart's activities. The electrocardiogram is not difficult to understand if one has a knowledge of the nature of the heart beat.
The heart beat comprises a threefold operation and not a twofold operation, as we have always been led to believe. The auricle has but one phase a slow contraction pushing the blood into the ventricle. The action of the ventricles is divided into two phases. The first phase is .a sharp contraction upon the contained fluid (blood), and the second phase is a firm, slow continuation of the primary phase, or sharp contraction, pushing the blood out of the heart.
Thus we have three definite phases, each generating an electric current. The first current known as the P current, produces the P wave, which represents the contraction of the auricles. The second current or R current produces the R wave which represents the contraction of the ventricles. The third current produces the T wave, representative of the work of the ventricles.
In every electrical picture of the heart beat these waves of electricity are to be identified.
One of the great difficulties encountered in attempting to teach the application of the electrocardiograph to heart conditions is the fact that most people have an entirely wrong conception of the nature of the heart beat. All the world knows that the auricle contracts first and then the ventricle, and every one knows that there are two sounds to the heart beat, the first and second sound. I don't suppose any one thinks that the contraction of the auricle and the first sound represent the same event, but many people have been puzzled to know why the ventricular contraction, which is apparently one event, should be accompanied by two events in tracings and cardiograms.
The electrocardiograph is able to show which part of the heart acts first and which part acts later, during all the various combinations that arise as impulses are generated in one part of the heart or another. Thus, if the ventricle acts before the auricle, we have the .high, sharp current in the shape of the church-steeple coming before the little, high mound that is so characteristic of the electric current from the auricle. If the impulse starts at the top of the ventricle and moves to the apex of the heart, we have the current moving in one direction and the church-steeple pointing upward. If, on the other hand, the impulse starts at the apex of the ventricle and journeys toward its base, we have the current travelling in the opposite direction and the church steeple pointing downward. These constitute a common disorder of the heart and one that is met with in many people who are otherwise healthy. Any form of tracing taken from the heart will reveal the order in which the heart beats are occurring; but it is only the electrocardiograph that will show the true nature of each individual beat of the heart and thus reveal all its more obscure vices.
One of the most important things which we have to do is to convince the public, both in the medical profession and without, that these observations by the cardiograph are as definite as are the observations of a surveyor or an astronomer; and that therefore the study of the disorders of the heart is no longer a matter of guess work but a definite determination. Our knowledge of the heart through the electrocardiograph is so recent having been begun only ten or fifteen years ago that the doctors who work in it must take it up as a new study.