Paul S. Barker

The determination and the significance of the areas of the ventricular deflections of the electrocardiogram

Abstract By measuring the areas of the ventricular deflections of the electrocardiogram it is possible to determine the mean electrical axis of QRS, which gives the direction in which the excitatory process spreads over the average element of ventricular muscle, and the mean electrical axis of T, which gives the inverse of the direction in which the recovery process spreads over the average element of ventricular muscle. If all the ventricular muscle passed through the period of excitation in the same time and in the same way, the area of QRS and the area of T would be equal in absolute magnitude, but opposite in sign, and the area of QRST would be zero. The area of QRST is a measure of the electrical effects produced by local variations in the excitatory process. The mean electrical axis of QRST gives the direction of the line along which these local variations are greatest. The local variations in the excitatory process which determine the mean electrical axis of QRST are dependent upon factors that act upon different parts of the ventricular muscle with different intensities. They are not materially influenced by the course of the excitatory process over the ventricular muscle.

Electrocardiograms that represent the potential variations of a single electrode

Abstract In order to simplify the analysis of the curves obtained by leading from the precordium and for certain other purposes, we have devised leads that record the potential variations of a single electrode. Electrodes are placed on the right arm, left arm, and left leg in the usual way and connected through like resistances to a central terminal. The resistances used for this purpose should be large in comparison with the resistance of the body in standard leads. Theoretical considerations and experiments on a model indicate that under these circumstances the potential variations of the central terminal are negligible. The curves obtained by leading from an exploring electrode in contact with any part of the body to the central terminal represent the variations in potential produced by the heartbeat in the region in contact with the former. The potential variations of the right arm, left arm, and left leg are recorded by leading from the electrodes placed on these extremities to the central terminal. They may be compared with the potential variations that occur in various parts of the precordium. To increase the resistance in the input circuit of our recording apparatus we have connected the string galvanometer to the balanced plate circuit of a one-stage vacuum-tube amplifier

The order of ventricular excitation in human bundle-branch block

Abstract Leads in which one electrode (the exploring electrode) is placed close to the heart and the other (the indifferent electrode) at a distance from it are semidirect leads. In experiments on dogs serial semidirect leads were taken from the surface of a pad of gauze soaked in warm normal salt solution and laid upon the exposed heart. The galvanometer connections were made in such a way that relative negativity of the exploring electrode yielded an upward deflection in the completed curve. In animals in which bundle-branch block had been produced, the chief upstroke of the ventricular complex occurred early in those semidirect leads in which the exploring electrode was close to the surface of the contralateral, and late in those leads in which this electrode was close to the surface of the homolateral ventricle. In the former case was usually negative; in the latter case, usually positive. In precordial leads the exploring electrode is placed on the precordium and the indifferent electrode on the left leg. Serial precordial leads in cases of clinical bundle-branch block of the common type yield results similar to those obtained by semidirect leads in experimental left branch block. In the rare type of bundle-branch block they yield results similar to those obtained in experimental right branch block. The common type of bundle-branch block is left branch block; the rare type, right branch block. The chief ventricular upstroke of semidirect leads, in which the exploring electrode is placed close to the ventricular surface, corresponds to the intrinsic deflection of direct leads from the ventricles in which a single contact is placed upon the muscle.

The excitatory process observed in the exposed human heart

Abstract 1. 1. A study of the arrival of the excitation process at a number of points on the surface of the human heart with reference to the beginning of R in Lead II was made. It was found that the order of excitation differs in some respects from that found by Lewis and Rothschild in the dog. The earliest points were on the anterior surface of the right ventricle near the atrio-ventricular border. Our results suggest that the conducting tracts in the right ventricle of man may differ from those of the dog. 2. 2. The curves produced by stimulation of various points on the surface of the human heart were recorded in the three standard leads taken simultaneously. These curves indicate that: 1. (a) Ventricular premature contractions of right ventricular origin are represented in the electrocardiogram by ventricular complexes in which the chief initial deflection is upward in Lead I. Ventricular premature contractions of left ventricular origin are represented in the electrocardiogram by ventricular complexes in which the chief initial deflection is downward in Lead I. 2. (b) The clinical electrocardiograms at present ascribed to block in the right branch of the His-bundle indicate block in the left branch, and vice versa . 3. (c) In so-called left ventricular preponderance the electrocardiogram is dominated by right ventricular effects and vice versa .

The mechanism of auricular paroxysmal tachycardia

A URICULAR paroxysmal tachycardia was long ago described and recognized as a clinical entity, but the fundamental mechanism or mechanisms responsible for this disorder have not yet been finally ascertained.‘, 2 Unlike auricular flutter and auricular fibrillation, it cannot be readily induced in experimental animals, and cannot, therefore, be easily studied by this met,hod. Speculations as to its nature must, therefore, be based on pertinent observations on man. We propose to discuss from this standpoint the following features of this disturbance : (1) the form of the anricular deflect.ions; (2) the effects of exertion, vagal stimulation, digitalis, quinidine, and other drugs upon the auricular rate and the duration of the paroxysms; (3) similarities, differences, and relations between it and auricular flutter and fibrillation; (4) the spontaneous occurrence of auriculoventricular block in a small number of cases and the difficulty or impossibility of producing it in most of the others; and (5) the occurrence of alternation in the auricular cycle length. We wish particularly to examine the su ggestion3 that auricular paroxysmal tachycardia is caused by circus rhythm involving one of the specialized auricular nodes. When Mines4 described circus rhythm he suggested that it might be responsible for some cases of paroxysmal. tachycardia in man. Iliescu and Sebastian? were among the first to su ggest that auricular paroxysmal tachycardia is due to circus contraction. Their reasoning was based chiefly on the a,ction of quinidine in this disorder. Lewis2 pointed out that the tot.al amount of auricular muscle is not sufficiently large to accommodate a circus mechanism at known rates of conduction in aurieular

A clinical type of paroxysmal tachycardia of ventricular origin in which paroxysms are induced by exertion

Abstract There is a type of paroxysmal ventricular tachycardia in which the abnormal mechanism is induced by emotion and exertion. The attacks may be long, but more often short attacks separated by periods of extrasystolic arrhythmia occur in rapid succession. In the majority of the cases there is no other evidence of cardiac disease. Patients with this disorder are usually seriously incapacitated. Small doses of quinidine are often strikingly beneficial but do not always prevent the occurrence of attacks. In one of the cases studied by the authors a long paroxysm of ventricular tachycardia was frequently interrupted temporarily by short attacks of paroxysmal auricular tachycardia.

The effects of alkalosis and of acidosis upon the human electrocardiogram

Abstract Much attention has been given to electrocardiographic changes caused by heart disease or by drugs used in the treatment of heart disease. Little notice has been taken of transient changes not related to heart disease. It has long been known that such changes may be caused by exercise, 1 drinking iced water, 2 stimulation of the vagus or sympathetic nerves, 1, 3, 4 and by alterations in the position of the heart such as may be produced by respiration or changes in posture. 1, 5 There have been a few observations upon the effects of alkalosis and of acidosis upon the electrocardiogram. In 1926, Schott 6 reported that in dogs the T-waves may be made taller by giving hydrochloric acid intravenously, and smaller by giving sodium carbonate intravenously. Transient reduction in the amplitude of T in man during the tetany of spontaneous overbreathing was reported in 1929 by Kronenberger and Ruffin, 7 and in 1932 by McCance. 8 Simpson 9 has observed reduction in the amplitude of T in patients undergoing artificial fever therapy, all of whom had alkalosis. An increase in the duration of electrical systole (the Q-T interval) in man has been observed by Bazett 10 following exercise, and by Carter and Andrus 11 in alkalosis. Samojloff 3 and Bazett noted an increase in the duration of systole after giving atropine. In various conditions in which the blood serum calcium is reduced the duration of electrical systole is increased, 11–14 while an elevation of serum calcium may be accompanied by a reduction in the duration of electrical systole. 12, 13, 15 The present study was prompted by the observation of T-wave changes occurring during an episode of hysterical overventilation with tetany.

Electrocardiograms of an unusual type in right bundle-branch block

Abstract There are certain cases of intraventricular block in which the ventricular complexes of the electrocardiograms show the following characteristics: In Lead I all the ventricular deflections are small. There is a conspicuous S deflection, and T is usually flat or upright. In Leads II and III the ventricular deflections are similar in all respects to those seen in bundle-branch block of the common variety. Precordial leads have been employed in three cases in which the standard electrocardiograms were of this kind. In these leads the ventricular complexes are like those that are recorded in dogs with right branch block and in patients with diphasic ventricular complexes of the rare type. It is thought that the curves referred to represent right branch block. Some additional factor that modifies the form of the electrocardiogram may be present.

The significance of electrocardiograms characterized by an abnormally long QRS interval and by broad S-deflections in lead I

Abstract Serial precordial leads have been used in an attempt to locate the conduction defect responsible for electrocardiograms characterized by a QRS interval measuring 0.12 second or more and by narrow R-deflections and broad S-deflections in Lead I. In Lead III there is a narrow Q or S deflection synchronous with R in Lead I and a broad upward deflection synchronous with S in the same lead. In cases in which the standard electrocardiogram is of this type precordial leads from the right side of the precordium show a very late chief upstroke; precordial leads from the left side of the precordium show an early chief upstroke approximately synchronous with the peak of R in Lead I. These curves are strikingly similar to those obtained by the same method of leading after section of the right branch of the His bundle in dogs. For this reason it is believed that electrocardiograms of the kind mentioned represent right bundle-branch block in man. There is much less difference in frequency between clinical right and clinical left branch block than has heretofore been supposed.

The potential variations produced by the heart beat at the apices of Einthoven's triangle

Abstract A method is described by means of which it is possible to determine the potential variations produced by the heart beat at any one or all of the apices of Einthovens equilateral triangle. It is consequently possible to determine the potential variations produced by the heart beat at any point of the body by leading from this point to the left leg, or the left or right arm, and subtracting the effect produced by the potential variations of this extremity from the recorded curve. It is possible by this method to free curves obtained by leading from points on or near the heart to points at a distance from it, such as points on the left leg, from the influence exerted by potential variations at the distant electrode.