Disturbances of the Heart | Page 4

the scientific therapy of heart disturbances. A complete section has been added on blood pressure.

PREFACE TO THE FIRST EDITION
That marvelous organ which, moment by moment and year by year, keeps consistently sending the blood on its path through the arteriovenous system is naturally one whose structure and function need to be carefully studied if one is to guard it when threatened by disease. This series of articles deals with heart therapy, not discussing the heart structurally and anatomically, but taking up in detail the various forms of the disturbances which may affect the heart. The cordial reception given by the readers of The Journal to this series of articles has warranted its issue in book form so that it may be slipped into the pocket for review at appropriate times, or kept on the desk for convenient reference.

CONTENTS
Preface Preface to First Edition Disturbances of the Heart in General Classification of Cardiac Disturbances Blood Pressure Hypertension Hypotension Pericarditis Myocardial Disturbances Endocarditis Chronic Diseases of the Valves Acute Cardiac Symptoms: Acute Heart Attack Diet and Baths in Heart Disease Heart Disease in Children and During Pregnancy Degenerations Cardiovascular Renal Disease Disturbances of the Heart Rate Toxic Disturbances and Heart Rate Miscellaneous Disturbances

DISTURBANCES OF THE HEART IN GENERAL
Of prime importance in the treatment of diseases of the heart is a determination of the exact, or at least approximately exact, condition of its structures and a determination of its ability to work.
This is not the place to describe its anatomy or its nervous mechanism or the newer instruments of precision in estimating the heart function, but they may be briefly itemized. It has now been known for some time that the primary stimulus of cardiac contraction generally occurs at the upper part of the right auricle, near its junction with the superior vena cava, and that this region may be the "timer" of the heart.
This is called the sinus node, or the sino-auricular node, and consists of a small bundle of fibers resembling muscle tissue. Lewis [Footnote: Lewis: Lecture in the Harvey Society, New York Academy of Medicine, Oct. 31, 1914.] describes this bundle as from 2 to 3 cm. in length, its upper end being continuous with the muscle fibers of the wall of the superior vena cava. Its lower end is continuous with the muscle fibers of the right auricle. From this node "the excitation wave is conducted radially along the muscular strands at a uniform rate of about a thousand millimeters per second to all portions of the auricular musculature."
Though a wonderfully tireless mechanism, this region may fall out of adjustment, and the stimuli proceeding from it may not be normal or act normally. It has been shown recently not only that there must be perfection of muscle, nerve and heart circulation but also that the various elements in solution in the blood must be in perfect amounts and relationship to each other for the heart stimulation to be normal. It has also been shown that if for any reason this region of the right auricle is disturbed, a stimulus or impulse might come from some other part of the auricle, or even from the ventricle, or from some point between them. Such stimulations may constitute auricular, ventricular or auriculoventricular extra contractions or extrasystoles, as they are termed. In the last few years it has been discovered that the auriculoventricular handle, or "bundle of His," has a necessary function of conductivity of auricular impulse to ventricular contraction. A temporary disturbance of this conductivity will cause a heart block, an intermittent disturbance will cause intermittent heart block (Stokes-Adams disease), and a prolonged disturbance, death. It has also been shown that extrasystoles, meaning irregular heart action, may be caused by impulses originating at the apex, at the base or at some point in the right ventricle.
In the ventricles, Lewis states, the Purkinje fibers act as the conducting agent, stimuli being conducted to all portions of the endocardium simultaneously at a rate of from 2,000 to 1,000 mm. per second. The ventricular muscle also aids in the conduction of the stimuli, but at a slower rate, 300 mm. per minute. The rate of conduction, Lewis believes, depends on the glycogen content of the structures, the Purkinje fibers, where conduction is most rapid, containing the largest amount of glycogen, the auricular musculature containing the next largest amount of glycogen, and the ventricular muscle fibers the least amount of glycogen.
Anatomists and histologists have more perfectly demonstrated the muscle fibers of the heart and the structure at and around the valves; the physiologic chemists have shown more clearly the action of drugs, metals and organic solutions on the heart; and the physiologists and clinicians with laboratory facilities have demonstrated by various new apparatus the action of the heart and the circulatory power under various conditions. It is