CHAPTER I
General Outline of the Principles Underlying the Production of Heart Failure
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1
The object of the circulation, and how it is attained.
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2
The importance of the heart muscle.
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3
The meaning of heart failure.
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4
Reserve force.
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5
Conditions exhausting the reserve force.
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6
The nature of the symptoms in heart failure.
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7
Methods adopted in describing affections of the heart.
As the study of the condition of the heart is approached in this book from a standpoint somewhat different from that usually taken in textbooks on diseases of the heart, I propose to give here a brief description of the principles underlying this method of study, in order that the reader may the more readily appreciate the nature and symptoms of heart failure.
1. The object of the circulation, and how it is attained.— The object of the circulation is the supply of a constant stream of material capable of nourishing the tissues, and of replacing the loss of energy sustained by them, and the removal of such waste products as are capable of entering the circulatory channels. In order to facilitate the exchange of products between the blood and the tissues, a certain degree of slowing of the flow takes place as the blood passes through the capillaries. As a continuous pressure is required to force the blood onwards, the intermittent pressure conveyed to the blood‐stream by the heart is converted by the resilient nature of the arterial walls into a constant pressure at the periphery of the arterial system. The maintenance of the arterial pressure is the outcome of the force exerted by the left ventricle, and of the resistance of the smaller arteries and capillaries. The full force of the ventricular contraction is not spent on the blood‐current merely during the period of its systole. In throwing the blood into the arterial system, it does so with such force that it distends to a slight extent the larger arteries. The elastic coats of the arteries, as soon as the ventricular systole is over, compress the column of blood within them, and in this manner maintain a degree of arterial pressure during the period that the ventricle is not acting. The ventricular force is thus stored up by the distension of the elastic coats of the arteries, and liberated during the ventricular diastole.
The principles underlying the mode of action of the left ventricle and the systemic circulation apply equally to the right ventricle and the pulmonary circulation.
2. The importance of the heart muscle.— The heart muscle supplies the force which maintains the circulation. In the normal condition, the mechanism of the circulation is so adjusted that all parts combine to facilitate the work of the heart and to attain the object of the circulation. Any disturbance of that adjustment must at once entail more work upon the heart muscle, inasmuch as a departure from the normal means the embarrassment of the heart in maintaining the normal arterial pressure. So long as the heart can overcome the impediment,'and maintain the circulation in a normal manner, no symptoms are evoked, but if the heart is no longer able to carry on the circulation efficiently, then certain phenomena at once arise, and these phenomena we call ‘symptoms of heart failure.’
3. The meaning of heart failure.— From this consideration it will be realized that heart failure is simply inability of the heart muscle to maintain the circulation, and that this failure of the heart muscle is due to a disturbance of the normal adjustment of the various factors concerned in the circulation. This disturbance may arise in a great many ways, but the end result is the same embarrassment of the heart muscle and its final exhaustion. The heart muscle therefore is of such prime importance in what we call heart failure, that a close and intimate study of its properties is essential. This will be dealt with later in some detail; here I want to call attention to a feature of the heart muscle which is the essential factor in the consideration of every form of heart failure, namely, the reserve force.
4. Reserve force.— The more I study the symptoms of heart failure, and the more I reflect on the part played by the heart muscle, the more convinced am I that the explanation of heart failure can be summed up in the general statement that heart failure is due to the exhaustion of the reserve force of the heart muscle as a whole, or of one or more of its functions. This statement may seem so self‐evident as scarcely to need amplification, but as a matter of fact, this, the essential principle on which diagnosis, prognosis, and treatment should be based, is often practically ignored. I shall make no apology for the continuous reiteration of this apparent truism, for the simple reason that in the study of all cases of heart failure, the condition of the reserve force will be found to be the ultimate question.
Although we recognize what reserve force is, it is not very easy to define it in words. Physiologists do not seem to have given it that study its importance demands. Although difficult to define, its existence is proved in every movement of the body, and in every effort which is made, as it is by the possession of this quality that we are able with ease to undertake all forms of effort. The estimation of the amount of reserve present is the best test of the heart's condition. It is the premature exhaustion of this reserve which constitutes heart failure, and it is the heart's power to regain this reserve force on which recovery from heart failure depends.
5. Conditions exhausting the reserve force.— I have already remarked that, in the normal condition, the adjustment of all parts concerned in carrying on the circulation is essential to efficiency. Any disturbance of the adjustment at once calls for an increased effort. Such calls are made first on the reserve force and, if persisted in, lead sooner or later to its exhaustion. These disturbances of the adjustment are extraordinarily varied in character, and may arise from any one of the factors on which the normal heart's action depends. It will be from this standpoint that the diseases of the heart will be studied, inasmuch as it is only by looking at the matter in this light that a proper perspective is obtained in regard to the significance of any abnormality. Thus, irregular action of the heart will be described from the point of view of its effect upon the efficient performance of the heart, as well as the condition producing it. Valvular defects will be studied not as a specific affection to be considered in themselves, but rather as a source of embarrassment to the heart muscle in its work. In the same manner, arterial degeneration and high blood‐pressure will be considered as conditions that upset the normal adjustment of the factors that carry on the circulation. Inherent defects of the muscular wall itself will also be viewed in their bearing on the heart's efficiency. The relative efficiency of independent functions of the muscle‐fibres will be kept constantly in view, inasmuch as organic lesions act deleteriously through disturbing their normal harmony. Depression of the individual functions may arise without any gross organic lesions, and lead to serious embarrassment of the circulation. While I am far from comprehending the full effect of functional depression, for the study of pure functional pathology is in its infancy, yet I hope the facts I detail may help forward a line of observation that promises much for future investigation.
6. The nature of the symptoms in heart failure.— Brieflyput, the symptoms are produced by the exhaustion of the reserve force. The first sign is invariably a subjective one, although it may for a time pass unnoticed. The patient's attention is first directed to his condition by some disagreeable sensation evoked when he attempts to perform some act which he had been wont to do with ease, and without distress. Such a condition can be summed up as due to the too speedy exhaustion of the reserve force, and manifested by a limitation of the field of cardiac response. The sensations by which the limitation makes itself known are varied, but when carefully analysed, the true nature of the heart failure is revealed. Hence, I insist upon particular attention being paid to the patient's sensations.
The standard by which one measures the strength of the heart, or more properly speaking, the amount of the reserve force, is in the main personal, as each individual unconsciously acquires the knowledge of what he can do with comfort, and his attention is called to the fact that his range of effort has become circumscribed. The observing physician can also detect signs in the frequent pulse and quickened respiration, out of proportion to the exertion. Other sources of information are obtained from the physical examination of the patient, not only in the heart itself, but in the condition of the circulation in other organs and tissues, as well as in the reflex protective phenomena which appear in affections of the heart as in affections of other viscera.
7. Methods adopted in describing affections of the heart.— The ideal method in writing a book on diseases of the heart would be to take up each separate lesion, and describe the symptoms that arise in consequence of the lesion. But although this method is the one that has been attempted by most writers of textbooks, it is impracticable in our present state of knowledge. Not only are the lesions imperfectly recognized, but the symptoms themselves are usually not the outcome of the organic lesion, but result from the embarrassment of the heart induced by the lesion. Thus the symptoms of heart failure in a case of valvular disease are not produced by the valve lesion, but by the failure of the heart muscle to overcome the difficulty created by the damaged valve, and this failure may be brought about in a variety of ways by the greater exhaustion of one function than of another,—sometimes, for example, it is the contractile power of the heart that gives way, sometimes the tonicity; so that we get a variety of symptoms corresponding to the exhaustion of different functions. But these functions may become exhausted from other causes than valvular lesions, and similar symptoms may therefore be induced by organic lesions of great diversity. Another reason for not following this ideal method is that it is extremely rare that the heart is the seat of only one lesion, or of a lesion limited to one particular part. Acute affections of the heart, for instance, are often described as endocarditis or pencarditis, because there happens to be a marked systolic murmur or a pericardial friction sound. But in addition to these audible signs, there may be presented a great number of symptoms such as dilatation of the heart, irregular action of the heart, and so forth, and these are given as being symptoms of the endocarditis or limitation of the field of cardiac response. pericarditis. As a matter of fact, these symptoms are not the outcome of endocarditis or pericarditis, but of a myocardial affection, and the attempt to give a precise description of the symptoms pertaining to each organic lesion has led writers to ascribe phenomena to lesions with which they have no connexion, with the result that the symptomatology of heart affections is today confused and contradictory.
In searching for a reason for this confusion, I am inclined to attribute it to the fact that the human mind attaches the greatest importance to that class of phenomena which most strongly affects the senses. Many of the really vital and all‐important symptoms are so subtle and so slight that it takes the most careful methods to detect them, whereas a roaring murmur or an irregular pulse thrusts itself upon our attention. The result is that the subtle signs are ignored and all the stress is laid upon the murmur and irregularity. Murmurs and irregularities therefore have come to occupy a far more important place in the cardiac symptomatology than their true significance merits.
These considerations have led me to adopt a method which I hope will place the symptoms in a proper perspective. Recognizing the fact that the attention of the physician or the patient is drawn to the heart by the appearance of one or more symptoms‐and it is only by the recognition of the symptoms that the diseases can be inferred, —I write this book from the standpoint of the symptoms. So far as I can, I describe each symptom, give its physiological meaning, and the various pathological conditions with which it may be associated. Then I try to estimate its significance. From the data thus obtained, conclusions are drawn as to prognosis and treatment.