cuit, the passage of these currents are indicated by the movements of the string. It is the photographic record of these movements on the moving sensitive paper which constitutes the electrocardiogram. The length of the wires. forming the circuit is practically immaterial, so that it is possible to make the records without moving the hospital patients from their beds, or without disturbing them in any way, provided wires can be led from the bedside to the galvanometer, as has been arranged in the hospitals in which the instrument is in use.

A record is obtained of the shadows of all objects which intercept the light passing from the arc lamp behind the galvanometer to the sensitive photographic paper, and so the shadow of the lever of a Jaquet chronograph hanging in front of the lens of the camera and ticking sidewise every fifth of a second shows on the record as a line interrupted every fifth of a second. This time record allows the distances on the record to be converted into time values, and the estimation of the rate per minute of any recurring movement of the string.

Lastly, let us explain how the movements of the cardiac muscles affect the string of the gal

by reason of the contractions of the cardiac muscles can be conducted through the string of the galvanometer. Of course, wires cannot be attached directly to the cardiac muscle, but they can be attached to the right arm and left leg, for instance. As the tissues of the body form a good conductor they serve to complete the circuit and when a wire is attached to the right arm, we have in reality a conductor leading from the base of the heart, first composed of the body tissues and then of the wire. The connection is made between the right arm and the wire by attaching a plate of German silver to the forearm by bandages soaked in salt solution. The wire is then attached to this plate by an ordinary screw connection. In this way a satisfactory electrical contact is made between the skin of the forearm and the wire.

By attaching a plate to the left leg and connecting it with a wire we have a conductor leading off from the apex of the heart. When the two wires are brought together to form a circuit, electrical currents pass through them during each movement of the cardiac muscle and when the string galvanometer is put in this cir

vanometer. The impulse of the cardiac contraction arises at the base of the heart where the superior vena cava enters the right auricle, so that the contraction begins there, and the base of the heart is rendered electrically negative to the apex. At the onset of the contraction of the auricles, therefore, a current passes through the wires from the left leg to the right arm and the string of the galvanometer is deflected. This deflection is recorded on the moving paper. The auricular contraction is very soon completed and the string of the galvanometer returns to its original position. The record shows a small upwardly directed wave of short duration resulting from the auricular systole. When the auricular activity has ceased there is an appreciable period of time before ventricular activity begins, a time during which the stimulus of the heart beat is passing from the auricles to the ventricles. The contraction of the ventricles, being more complex, causes not one but a series of deflections of the string, and is, therefore, represented in the record by a series of waves. There is first a small downwardly directed or negative wave followed im

mediately by a tall, sharp, positive wave which ends in a second small negative wave. These three waves occur when the stimulus first reaches the ventricles, and when the basal portion of the ventricles is in contraction while the apical portion is still at rest. When the contraction has spread throughout the ventricles the string returns again to its original position, as no current is then passing through the wires. As diastole of the ventricles sets in, however, the main portion of the ventricles relax before

No condition illustrates the incoordination of the auricles and ventricles so well as that of complete heart block, and a series of curves from such a case is shown to illustrate this point as well as to demonstrate several interesting features of this disease, which can be demonstrated in the records. The first curve from this case shows the waves of auricular activity occurring regularly at a rate of 68.6 per minute (marked p), while the waves of ventricular activity (marked r and t) occur at a rate of

the portion about the aortic and pulmonic valves, and a final current passes through the wires, just as it does at the end of the contraction of an ordinary muscle. The final current causes a deflection of the string, which is recorded as a rather long positive wave marking the end of the ventricular systole. During diastole no currents pass, and as the string remains in its original position, this part of the cardiac cycle is represented by a straight line in the

curve.

The wave representing the auricular contraction and the four waves representing the ventricular contractions have been designated by five consecutive letters of the alphabet: p, q. r,

27.3 per minute. It is also seen that the relation of the waves to the r waves, which is constant in the record of the normal heart, is here wanting, and the record indicates that the two parts of the heart are beating entirely independently. In this case the patient had a definite history of syphilis and a strongly positive Wassermann reaction, so that it is fair to assume that a syphilitic lesion has involved the auriculo-ventricular bundle, thus preventing the passage of the stimuli of the heart from the auricles to the ventricles. This has forced the ventricles to establish their own rhythm at their characteristic slow rate in order to maintain the circulation.

s and t. As the g and s waves are usually inconspicuous they have not been marked on the curves to be shown, while the positive waves, p, r and t, are lettered.

It will be seen from the curves that the wave of auricular activity can be readily distinguished from those representing the ventricular activity, so that there is no difficulty in determining whether or not the two parts of the heart have a normal coordination.

The first curve was obtained from a normal individual and shows the normal relation of the auricular and ventricular activity. The various waves that have been described can be seen.

The second record from this case demonstrates the fact that the auricular and ventricular rates are quite independent. Here the auricles are beating at the same rate as before, while the ventricles are beating at a distinctly faster rate, i. e., 42.2 per minute, instead of 27.

The third record shows the occurrence of marked ventricular arhythmia. Two ventricular cycles are seen, one having a duration of 2.4 seconds and the second of 4.2 seconds. This ventricular arhythmia occurs without any change in the auricular rhythm. It is on the occurrence of these ventricular pauses that a very significant feature of the clinical picture

depends. These pauses were of sufficient duration at times to produce unconsciousness and mild transient convulsions, dependent doubtless on the cerebral anemia which resulted from the ventricular stoppages. These pauses lasted not infrequently thirty-five seconds, judging from the absence of the radial pulse and heart sounds. Unfortunately, electrocardiograms could not be obtained during one of these seizures, which characterize the case as typical of the AdamsStokes syndrome.

that for the most part the cardiac contractions are recorded by a normal series of waves. The wave representing the auricular contraction, having a normal relation to the subsequent r and t waves, and that these waves occur regularly. Following the first and seventh normal complexes, however, there appear much larger waves of abnormal form, occurring earlier than the regular time for the normal waves. These larger waves are caused by a premature ventricular contraction, the impulse for which

unaffected.

The fourth record demonstrates further the physiological dependence of auricles and ventricles in complete heart-block. While the record was being made the right vagus nerve was stimulated by pressing over it in the neck. The points at which the pressure was exerted and released are indicated in the curve. The usual action of vagus stimulation, slowing of the heart, was effectual on the auricles only, while there was no change in the ventricular rate. This same dependence was demonstrated by records taken every five minutes during the hour following the hypodermic injection of 30 grain of atropin sulphate. As is well known, this drug paralyzes the vagus endings in the

arose in the ventricle itself, the auricles playing no rôle in the ventricular stimulation in these instances. We have here an example of the so-called extra systoles, a well-known and common cause of cardiac irregularity. The contraction of the ventricles, beginning at an unusual point in the muscle, follows an unusual course and, therefore, causes an unusual electrical reaction, which results in this abnormal wave. It is seen that this abnormal wave is followed by a pause, and measurements show that the rhythm of the regular waves is disturbed only by having one omitted immediately after the abnormal wave. This results from the fact that the auricular rhythm is not dis

heart, releasing it from the vagal control and causing a marked increase in the heart rate.. The records show that the auricular rate increased 23 beats per minute, while the ventricular rate was practically unchanged. These procedures illustrate how well the electrocardiograph is adapted for recording interesting and valuable investigations of the heart which can scarcely be obtained in any other way.

The next record was obtained from a patient under treatment in our dispensary and shows an entirely different type of incoordination between the auricles and ventricles. It is seen

turbed, but that the impulses furnished by the auricular contractions at the times of the ventricular extra systoles are ineffective in the already contracted ventricles. These premature ventricular beats or extra systoles, although producing these large waves in the electrocardiogram are in reality weak, inefficient contractions and produce but a weak radial pulse. It is the ventricular contraction following the pause which is abnormally strong and which gives rise to the subjection sensation of thumping. The ventricles have gathered extra strength during the prolonged diastolic rest.

and contract with a corresponding vigor, but it is seen that these contractions produce records practically identical with those caused by the usual heart-beats. This point is brought out to demonstrate the fact that no conclusions as to the force of the ventricular contractions can be drawn from the size of the waves produced. The differences in the electrical potential which governs the size of the waves, being dependent on other factors.

The occurrence of premature ventricular contractions has in itself no serious prognostic

ularity constitutes about 50 per cent. of all forms of arhythmia that are met with, and its definite diagnosis by means of the electrocardiograph is one of the most useful purposes of the instrument. It is in this condition that digitalis is of the greatest benefit. The drug diminishes the ease with which the abnormal auricular activity stimulates the ventricles, and thus lessens the frequency of the ventricular contractions. This is almost invariably followed by an improvement of the circulatory condition. Although in untreated cases the ventricles are

import. They not infrequently occur in healthy individuals, but especially those of neurotic temperament. The patient from which this record was made suffers from chronic myocarditis and mitral insufficiency, but who no longer shows premature ventricular systoles after a course of digitalis therapy.

The seventh record shows a type of cardiac disorder frequently met with, which remained obscure until its nature was revealed by the electrocardiograph. It is seen that the tall waves of ventricular origin occur irregularly at

usually beating with marked irregularity both in force and rhythm and at an abnormally rapid rate, cases under digitalis therapy may show a ventricular rate not exceeding the normal and the ventricular arhythmia may markedly dimin1sh. The eighth record is from such a case, and although the undulations between the ventricular waves are seen showing that auricular fibrillation is present, the ventricles show but slight irregularity and are beating at a rate of 76 per minute. Digitalis therapy in these cases should be directed towards obtaining such a result,

a rate of 118 per minute and that they are not preceded by any definite wave representing auricular activity. Between the ventricular waves the record shows a slightly undulating line. It has been demonstrated by the experiments of Lewis and of Rothberger and Winterberg that this form of record is obtained when the auricles no longer show their normal rhythmical contractions, but instead are possessed of a rapid, tumultuous, incoordinated activity known as fibrillation. This auricular activity sends stimuli to the ventricles irregularly and usually at a rate too rapid to maintain the circulation efficiently. This form of cardiac irreg

when patients with auricular fibrillation can be not infrequently maintained at a fairly high level of efficiency.

These few curves from cases of complete heart-block, ventricular premature contractions or extra systoles and auricular fibrillation serve to demonstrate the importance of the conception of the heart-beat, that its normal mechanism is dependent on a proper coordination of the two separately contracting portions of the heart, and that the electrocardiograph serves to demonstrate clearly any derangement of this coordination that may occur.

1806 Locust Street.

CARDIAC ARHYTHMIA *

P. T. BOHAN, M.D. KANSAS CITY, MO.

Only recently, in the diagnosis of heart disease, has much attention been paid to the disturbance of rhythm. Some arhythmias have no significance, the only value of their recognition being an assurance to the patient that they do not mean heart disease; while, on the other hand, others may be the only objective symptom of heart failure. In fact, heart failure may be the result of abnormal rhythm. The nature of cardiac arhythmia is no longer a mystery, but one of the best understood subjects in the whole science of medicine.

A clear understanding of the irregularities has been made possible by means of the polygraph and electrocardiograph. However, if the principles of arhythmia are understood, a correct diagnosis can be made in the majority of cases by merely feeling the pulse and auscultating the heart.

When the rhythm of the heart is normal, all the beats occupy the same space of time and are the same size. Any deviation therefrom is known as an irregularity or an arhythmia. Normally, the impulse for contraction of the heart begins at the base of the right auricle and passes along the wall of the auricle over His' bundle to the ventricle.

In embryonic life the heart is in the form of a tube and, where the vena cava empty into it, there is a dilated portion which is called the sinus venosus. In the development of the heart the sinus venosus becomes incorporated in the wall of the right auricle and the mouths of the great veins.

The sinus venosus cannot be recognized macroscopically in the mammalian heart, and the few embryonic muscle and nerve cells that constitute this important area were discovered by Keith and Flack, hence the term "the node of Keith and Flack" or "sinus node." In a frog the sinus venosus is a pouch of considerable size, and during a cardiac cycle (a frog's heart beats only eight or ten times a minute) one can see distinctly the contraction of the sinus; then, after an appreciable interval, the contraction of the auricle, and lastly the systole of the ventricle. Normally, the impulse for contraction always begins in the sinus; but it may originate at any point in the wall of either auricle or ventricle, in the node of Tawara, or in the bundle of His.

Although the heart will beat regularly after all connections with the nervous system are severed (section of the vagi and the sympathetics), the nervous system, through the two antagonistic nerve supplies, is constantly exerting an

* Read in the General Session of the Missouri State Medical Association, at the Fifty-Seventh Annual Meeting held at Joplin, May 12-14, 1914.

influence on the sinus. The sympathetic nerve is the accelerator, its function being to increase the rate and force of the heart-beat; hence, the tachycardia in all conditions in which the chromaffin system is overactive, such as exophthalmic goiter, and in cases of neurosis associated with or due to hypersympathetic tonus. In most cases where the heart rate is increased as a result of stimulation of the sympathetic nerve, the rhythm is normal unless there is a disease of the heart muscle.

A clear understanding of the vagus nerve and its function is of the greatest importance in the study of cardiac arhythmia, because many of the irregularities are due to altered vagal tone. A source of irritation in any viscus rhythm of the heart. Hoover1 reports a case of supplied by the vagus may alter the rate or heart-block due to reflex vagus inhibition caused by a thrombus in the right femoral vein. In childhood unstable vagal tone is particularly common, and, as I shall show later, is the sole cause of the heart's irregularities in the majority of cases under twelve years of age.

Experimental work by A. E. Cohn would indicate that there is a difference in the action of the two vagi nerves on the heart. In a dog he found that stimulation of the right vagus produced a slow action of the whole heart, due to lessened rate of stimulus formation in the sinus; while stimulation of the left vagus produced heart-block by lessening the function of the bundle of His. A slow pulse or disturbed rhythm due to vagus stimulation can be relieved by atropin.

PULSE TRACING

Although the vast majority of cases of arhythmia can be diagnosed without any graphic records, such a diagnosis is not possible. unless one has a clear idea of a normal tracing and the characteristic features of a tracing in each form of arhythmia. The instrument that records most accurately the events of a cardiac cycle is the electrocardiograph. However, this instrument is so expensive, so large and cumbersome, so difficult to manipulate, and the knowledge obtained by its use so slight in addition to that which can be secured by other more economical and less complicated methods, that it probably will never be in general use.

In my work I use the Mackenzie ink writing polygraph, a picture of which is shown in Figure 1. By means of this instrument a tracing can be taken simultaneously of any two given pulsations, the ones of the most importance being the radial artery and the jugular vein; but a record can also be obtained of the apex beat, the liver impulse and the respiratory

1. Osler's Modern Medicine, iv, 279.

2. Cohn "On the differences in the effects of stimulation of the two vagus nerves on the rate and conduction of the dog's heart." Jour. Exper. Med., 1912, xv, 49.