III. Pathological Relations

The complex circulatory apparatus is subject to many forms of derangement and disease, a few only of which require to be noticed for the purpose of illustrating the application of drugs and other therapeutical measures.

1. Disorders of the heart and vessels belong chiefly to three classes, according to their causes: (a) They may be due to direct nervous causes, such as mental excitement or depression, or to some cause acting reflexly through 'the nervous centres in the medulla, such as derangement of the stomach, intestines, uterus, etc. (b) They may originate in morbid states of the blood, especially anaemia, which disturbs the centres in the medulla, the vessels, and the nervo-muscular structures in the heart. Or (c) they may be traced to a poison in the system, e.g. tobacco, tea, alcohol, lead, and the poison of gout, each of which has a specific action on some part of the mechanism.

2. Organic disease will be sufficiently illustrated by a well-marked case of progressive heart disease from some morbid state of the aortic valves. These valves, from their position and constant movement, are peculiarly subject to disease. They thus become distorted or even destroyed, and rendered unfit to direct the movements of the blood, which is consequently obstructed in its exit from the heart in systole, and regurgitates from the aorta during diastole. The great power of adaptation to change of circumstances possessed by the circulation is generally sufficient to compensate for moderate valvular disease, by hypertrophy of the muscular walls of the heart. The serious symptoms set in when compensation fails, i.e. as a rule, when the nutrition of the ventricular wall is insufficient to supply the increased-possibly ever-increasing-demand for muscular force. The order of events is then as follows: systole fails to overcome the intraventricular pressure; the chamber is imperfectly emptied, and therefore over-distended in diastole; the walls are stretched; and the cavity is dilated. Pain and "oppression " make their appearance at this stage, and cause great distress. Henceforth derangement proceeds apace. With the dilatation of the chamber, the mitral valve becomes incompetent or misfitting; blood regurgitates in systole into the left auricle; the pulmonary circulation becomes over-distended; the obstruction makes itself felt in the right ventricle; and, after a time, in the right auricle, by forcing the tricuspid. The systemic veins now become congested from obstruction a fronte; the viscera become loaded with venous blood; their functions are disordered; and haemorrhage, dropsy, fluxes of plasma from the bowels and bronchi, and discharges of albumen in the urine occur. These derangements, coupled with those of respiration, the cardiac distress, and the effects of anaemia from imperfect arterial supply, finally render life impossible. During this process of backward dilatation, the cardiac action is necessarily disordered in all respects, the strength and regularity of the pulse giving way, and its rate being decidedly accelerated.

3. Hemorrhage

Hemorrhage. Bleeding produces certain effects on the system, partly referable to loss of blood, and partly to fall of the blood pressure. It is naturally arrested by this fall of pressure, by coagulation of the blood at the seat of disease, and by retraction of part of the coats of the vessel. If the haemorrhage be severe, fainting or syncope occurs, that is, loss of consciousness from failure of the heart and consequent deficiency of blood and blood pressure in the brain. Any other cause of cardiac failure will produce the same effect. At the same time, the weight of the body cannot be supported on account of the general muscular paralysis, which is another result of the ! cerebral anaemia; and the patient falls. The recumbency fortunately has a favourable effect: it restores the circulation through the cardiac and vaso-motor centres, increasing their activity; and renders the cerebral centres more responsive to afferent impressions.

IV. Natural Recovery

The whole circulatory system is furnished with so many and so accurate regulating and compensating mechanisms, that not only the great range of normal conditions to which it is exposed, but even many morbid changes, can be successfully met. The chief of these provisions for preventing or counteracting disease are the reserve force of the heart; the power of compensatory hypertrophy; the depressor mechanism; the arrangements for relief of the vessels by escape of the fluid portions of the blood through the kidneys and bowels, and into serous spaces; and the natural mode of recovery from haemorrhage and syncope. All these methods of natural relief or recovery are full of suggestions to the therapeutist, and rational treatment must follow nature's lines. The two circumstances which chiefly set a limit to compensation are failure of the coronary arteries to supply the hypertrophied walls, and suddenness of the cardiac lesion, which may hopelessly disturb the circulation before there is time for hypertrophy to occur.

V. Therapeutics

Although the details contained in the four preceding sections are very numerous and complex, the rational therapeutics of the diseases of the heart and vessels can be sufficiently illustrated by a few simple principles. The grand fact that stands out prominently amongst all the others is that dilatation must be prevented or relieved. It is a purely physical effect or state, resulting from the failure of the great physiological condition on which alone the circulation can be and is carried on, namely, that the driving power must always be greater than the resistance, i.e. whilst it varies with it, it must never fall below it. There are many other indications for treatment, but none that approach this in importance.

The general treatment of disorder and disease of the heart will mainly consist in ensuring an equable manner of life. Extraordinary influences of every kind, bodily and mental, especially exertion and excitement, must be shunned by persons suffering from cardiac disease, or in whom any of its common causes may be at work. When disease attacks the valves (endocarditis), e.g. in acute rheumatism, absolute bodily rest is essential to relieve the strain from them and the frequency of their movements; and cardiac depressants, such as Potash, Aconite, and Veratria, are employed to assist this effect.