Defects of the Valves of the Heart.—The thickening, calcification, or shrinking of the valves brings about a condition which prevents their closing. This may give rise to an increased supply of blood to one or the other portion of the heart. Owing to adhesions and ring-shaped calcifications, a narrowing of the valvular openings may take place which prevents one or more portions of the heart from completely emptying their contents. Both of these conditions—imperfect closing and permanent opening— modify the entire circulatory mechanism, and cause severe disturbances of the normal movement of the blood-stream. In its endeavour to compensate for these disturbances the heart performs an increased amount of work. This will either cause its muscular walls to become thicker (enlargement, or hypertrophy, of the heart) ; or it will give rise to enlargement of certain chambers of the heart, which may occasionally assume great dimensions, causing dilatation of the entire organ.
The heart is often able to carry on this increased amount of work for decades without relaxing. But as soon as the increased muscular power of the heart becomes insufficient, very pronounced manifestations of cardiac weakness develop. These signs are characteristic also of many other affec tions of the heart. The speed of the blood-current decreases throughout the capillaries, and symptoms of congestion develop in all organs. This causes blood-serum to escape into the tissues, giving rise to the condition known as DROPSY. The skin covering those parts of the body which lire remote from the heart becomes cool and dry and of a bluish discoloration ; the veins of the skin become more markedly dilated ; and the lungs become congested because of an increased supply of blood, thus giving rise to difficulty in breathing. At times, a painful cough develops, with profuse expectoration of reddish, often bloody, sputum. Palpitation of the heart is an early symptom of weakness, and constant sensations of oppression and fear prevail. The condition may cause disturbances also of the alimen tary functions ; and the urine usually becomes highly concentrated, and is voided in very small quantities.
Valvular defects of the heart are brought about, especially during childhood and adolescence, by a number of infectious diseases. In these affections the bacteria circulating in the blood or their poisonous secretions may cause new growths or inflammatory changes in the valves. This is very frequently the case in articular rheumatism and in septimmia. Although of less frequent occurrence in diphtheria, scarlatina, pneumonia, chorea, typhoid fever, erysipelas, and gonorrhcea, it should always be thought of as a possible complication in these diseases. A calcification of the main artery
(the aorta) may, especially in advanced age, extend into, and cause defects of, the valves of the heart. Valvular defects are very rarely congenital ; and they are seldom due to external injuries to the chest.
In many cases of cardiac valvular defects the condition does not become manifest at the onset, especially when the existing disturbances are fully compensated for by the increased activity of the heart. It is possible, there fore, that such a defect may remain unobserved for a long time. In ad vanced cases the characteristic symptoms may arise during temporary or permanent attacks of cardiac weakness. It is possible to afford a con siderable amount of comfort to patients suffering from such valvular disturbances, particularly when they are present in the milder degrees. Even very sick patients may be greatly benefited. See General Rules for the Prevention and Treatment of Heart-Diseases.
Enlargement of the Heart.—This condition may result from a thickening of the walls of the heart or from a widening of the heart-cavities (dilata tion). These morbid conditions of the heart are usually associated with each other. They may affect either the entire heart or only a part of it— as, for instance, the right or the left chamber. The chief causes of enlarge ment of the heart are valvular defects and calcification of the arteries (arteriosclerosis). Inflammation of the kidneys, expansion of the lungs, constant bodily over-exertion, high living, alcoholism, and permanent men tal excitement are other potent causes. Dilatation of the heart may occur from the same causes, and may develop also as a result of inflammation of the heart-muscle (myoc«rditis) or in consequence of severe febrile affec tions, as typhoid fever or pneumonia. Acute dilatation frequently occurs during an excess of athletic exercises. The principal disturbances ex perienced by the patient are shortness of breath, with attacks of dizziness and fainting. For the principles of treatment, see General Rules for the Prevention and Treatment of Heart-Diseases.
Fatty Degeneration of the Heart.—This affection is due to certain changes in the heart-muscle, induced by excessive fat, and giving rise to uniform symptoms. One form, the so-called " fatty heart " (usually a part symptom of general obesity), is brought about by the excessive deposit of fat below the heart in the pericardium or by an infiltration of the fat between the muscle-bundles of the cardiac muscle. In the former case the heart is pressed upon by the pericardium ; in the latter, its activity is impaired by a diminution of the firmness and strength of its muscle.