2. Parenchymatous Degeneration.—The relation of inflammation of the heart-substance to this degeneration is still somewhat indefinite. I have under Myocarditis described an acute interstitial form characterized by inter-fibrillar swelling with exudation and proliferation of corpuscles, and often granular or fatty degeneration of the muscle-cells. These changes may certainly be regarded as inflammatory, and they are met with either in association with endo- or pericarditis or in connection with specific fevers. Under the term parenchymatous degeneration or cloudy swelling Virchow described24 a change of frequent occurrence in the heart-muscle and elsewhere, which I think should be distinguished from myositis, although the two processes may lead to alterations difficult to distinguish macroscopically. It is characterized by a pale, turbid state of the cardiac muscle, general, not limited, and a relaxed, soft, brittle condition of the walls. The turbidity and softness are the special features; there are no peri- or endocardial changes—simply the loss of color and consistence. It is the softened heart of Laennec and of Louis; and Stokes speaks of an instance in which "so great was the softening of the organ that when the heart was grasped by the great vessels and held with the apex pointing upward, it fell down over the hand, covering it like the cap of a large mushroom."25 Microscopically, the fibres are indistinct, the protoplasm occupied by fine granules which obscure the striæ, and sometimes the nuclei. Proliferative changes rarely occur, although swelling and multiplication of the nuclei and the interstitial cells have been described. The granules may be extremely minute, or so large that they are mistaken for fat. They are generally uniform in size, and are scattered irregularly through the fibres. In extreme grades the entire fibre may be occupied by them, and no trace of structure can be seen. Dilute acids and alkalies dissolve the granules, but they resist the action of ether, indicating their albuminous nature. This condition is met with in the infectious diseases—typhoid, typhus, small-pox, pyæmia, remittent fever, etc.—particularly when the disease is protracted and the temperature high. Apparently, we must regard it as an expression of the effect of the poison upon the metabolism of the fibres, inducing a separation of albuminous particles in a granular form. That the high temperature alone does not produce it is demonstrated by its absence in many other diseases in which this condition prevails. The relation to fatty degeneration is not clear. It would appear to precede the development of this change.
24 Archiv, vi.
25 Diseases of the Heart, Am. ed., p. 373.
The effect of this degeneration is virtually the same as that of myocarditis, already described. It produces the weak heart of fever so well described by Stokes,26 with indistinct impulse, feeble or imperceptible first sound, and progressive diminution of contractile power. There is often a great reduction in the number of beats, which may sink to 40 or 50 per minute. In severe cases of typhoid fever we often have an opportunity of studying the progressive enfeeblement of the heart with weakening or disappearance of the first sound.
26 Loc. cit., chap. vii.
To Stokes we are indebted for the suggestion of the use of alcohol in this condition, and the experience of the past forty years has fully confirmed this practice of the Dublin school.
3. Fatty Heart.—Two conditions of the heart are recognized under this heading—viz. fatty infiltration and fatty degeneration.
Fatty Infiltration.—Cor adiposum, Lipomatosis cordis, and Fatty hypertrophy or overgrowth are synonyms found in the older and more recent works.
A condition in which there is an excess of fat beneath the pericardium and a growth of the same between the fibres of the myocardium. There is normally a certain amount of fat in the cardiac groves, particularly the auriculo-ventricular, and along the coronary arteries. An excess is not infrequently met with in connection with general atrophy, whether the result of disease or the natural decay of old age. Here it serves as padding, and has no pathological significance. In very corpulent persons there is always much subpericardial fat; it forms a part of the general obesity, and in this state an excessive accumulation may lead to a dangerous or even fatal impairment of the contractile power of the heart. Obesity is the expression of a morbid tendency, generally hereditary, to the deposition of fat in the connective tissues. A sedentary life and the consumption of food rich in carbohydrates favor this tendency, but we see it arise under conditions just the opposite when the predisposition to polysarcia is marked. Males are more usually affected than females, at least in Great Britain and Germany.
In the inspection of the bodies of very corpulent persons we find the mediastinum occupied by masses of fat which may completely cover the pericardium. The entire heart may be enveloped in a thick sheeting of fat, through which not a trace of muscle-substance can be seen. Along the groves, the regions of normal deposit, the layer may be an inch or more in diameter. In some cases the muscle-substance beneath seems but slightly involved; there may be superficial infiltration and penetration of columns of fat between the bundles, but the thickness of musculature is normal, and apart from the excessive deposition there is not much amiss. In other instances the muscle-substance is seriously affected; on section of the ventricular wall the fat is seen to infiltrate the entire muscle, separating strands of fibres and reaching almost to the endocardium. There may be places, indeed, in the thinner parts of the ventricular walls in which there appears to be complete substitution of the muscle by fat. Even the papillary bundles may contain adipose tissue. The chambers are usually dilated and the entire organ soft and relaxed. Microscopically, the fat-cells are everywhere seen infiltrating the muscle-tissue, separating the fibres and inducing atrophy. In some cases, even when the condition is advanced, the muscle-fibres appear normal, but in the majority fatty degeneration is also present. Often in these cases the coronary vessels will be found atheromatous.