ATROPHY.
Simple, eccentric, concentric. Usually eccentric. Causes, effusion in pericardium, obstruction of coronary arteries, by false membranes, etc., general inanition. Symptoms, beats weak, sounds loud, clear, decreased area of dulness on percussion, pulse slow, weak, under excitement unequal, irregular, intermittent with palpitation, dropsy of limbs, etc., murmur with 1st sound. Treatment only in early stages by removal of the cause.
The loss of substance in the muscular walls of the heart is either simple when there is no change in the capacity of its different cavities:—eccentric when the chambers of the heart are enlarged; or concentric when these chambers are reduced in size. Like hypertrophy it may affect the walls of one chamber to the exclusion of the others.
Atrophy is much less frequent in the lower animals than hypertrophy and in nearly all cases on record it was associated with dilatation.
The causes are not always very evident. Effusion into the pericardium is one of the most frequent, the compression of the heart impairing its nutrition and decreasing its size. Especially is it hurtful when several layers of false membranes deposited on the surface of the heart become organized, preventing its sufficient dilatation and compressing its nutrient bloodvessels. A case of this kind in a dog occurred to Leblanc; the right auriculo-ventricular opening was surrounded by thick organized layers of false membranes which by their contraction had largely diminished the opening and even pressed on the coronary artery cutting off to a great extent the supply of blood to the walls of the ventricle. Another alleged cause is a prolonged insufficient nourishment to the entire body. Leblanc has also observed this in dogs the subjects of long continued wasting maladies.
Symptoms. In pure atrophy these are the opposite of those seen in hypertrophy. The beats of the heart are weak or inappreciable to the hand placed on the side of the chest behind the left elbow. The sounds of the heart are loud and clear, their intensity being proportionate to the thinning of the walls and the dilatation of the chambers. Percussion so far as it can be made effectual, which is chiefly in dogs, shows a diminished area of dulness. The pulse is slow, weak, or indistinct, compressible, becoming accelerated, unequal, irregular, and intermittent when the patient is excited. Palpitation is frequent, breathing is difficult or easily embarrassed and there is a tendency to dropsy of the limbs and dependent parts. These symptoms are usually associated with considerable prostration and depression.
These are often complicated by symptoms of valvular disease or dilatation.
Atrophy progresses slowly and rarely causes death in the earlier stages. In its advanced stages when dropsy has supervened little can be done even in its mitigation. In the earliest stages only can good be done by employing measures calculated to remove its causes and thus put a stop to its progress.