Etiology.—Both in secondary and pri mary forms of hypertrophy, as well as in chronic myocarditis and chronic pericar ditis, fatty degeneration may super vene. The degeneration of the cardiac walls dependent upon valvular disease, Bright's disease, and general arterio sclerosis is, perhaps, more often fibroid than fatty in nature.
Valvular lesions produced artificially in dogs, cardiac hypertrophy ensuing. The compensation could only be broken by disturbing the innervation (e.g., by section of the vagus nerve). Fatty de generation of the heart of itself is not capable of producing loss of compensa tion. Phosphorus was administered to dogs with valve-lesions, and although at necropsy the heart was found quite fatty, compensation had been undis turbed. The writer maintains, there fore, that it is chiefly through disturb ances of the nervous mechanism of the heart that failing compensation is brought about. R. Bulint (Dent. med. Woch., Jan. G-13, 'OS).
It is constantly met, also, in associa tion with fatty change in other organs, in the severe forms of primary and sec ondary anminias, and even more com monly, though of a less severe grade, in the cachectic states produced by such chronic diseases as carcinoma and phthisis.
Results of investigations render it ex tremely doubtful whether the fatty changes found in pernicous anemias are due to the blood-condition. Kraus and Chvostek (Wiener klin. Woch., No. 33, '91).
The condition may arise in the course of acute infectious diseases of intense type, especially diphtheria and typhoid fever.
Fatty degeneration is extremely com mon in diphtheria, fatty degeneration appearing in 14 out of 19 animals (guinea-pigs, rabbits, kittens) inocu lated with the bacillus diphtheria; or its products. It appears to depend more on the intensity of the poison than on the time of its action. Simon Flexner (Johns Hopkins Hosp. Bull., Mar., '94).
Certain toxic agents (arsenic, phos phorus, alcohol) are potent to cause a high grade of fatty degeneration. In the case of alcohol, it is only after long periods of intemperance that cardiac de generation is established, and often only after primary coronary sclerosis. Be sides sclerosis, which is an all-important etiological factor, the condition may be consequent upon a mere blocking of the mouths of these vessels.
Fatty degeneration is most common after forty years of age.
Fatty degeneration of the heart is an uncommon occurrence in early life.
Case observed in a young man, aged 22, apparently robust, who, after a rapid walk of about two miles suddenly fell down, dying instantly. Marked fatty degeneration of the pericardium and heart was found. Lowther (Brit. Med. Jour., Oct., '90).
It occurs somewhat more frequently in men than in women, notwithstanding the fact that there are predisposing in fluences at work in the latter that do not obtain in the male sex, such as childbirth and amenorrhoea. Whatever may be its apparent etiology, it is invariably ceded by a defective nutritive supply to the muscle-cells; this may be dependent on mechanical causes, such as narrowing of the lumen of the coronary vessels, or upon impairment of the oxygen-carrying power of the blood, as in the anmmias.
[An important point in fatty degen eration is that the primary change is atrophy of the muscle-substance, and the fatty degeneration is secondary to this and consequent upon it. Disease of the coronary arteries being thus a cause of degeneration of the heart, the exist ence of conditions which may lead to the implication of the coronary arteries or their orifices in morbid processes will warrant a suspicion that cardiac weak ness, which may be recognized, is the result of degeneration. But there may be fatty degeneration of the heart when the coronary arteries are healthy. It is usually present, sometimes in a very ad vanced degree, in pernicious anemia, and granular degeneration, which is an acute form of the disease, is a constant effect of severe typhoid fever and of fatal phosphorus poisoning. Diabetes, alco holic excess, and a sedentary mode of life may conduce to fatty degeneration of the heart, probably through deterio ration of the blood, or it may be sec ondary to myocarditis. WHITTIER, VICKERY, and GREENE, Assoc. Eds., An nual, '92.] Fatty degeneration of the heart is, as a rule, simply a consequence of starva tion. This may be brought about through poverty of the blood itself, or through inability on the part of the blood-vessels to nourish the heart, ow ing to atheromatous changes in the vessel-walls or to chronic endarteritis. Mitral insufficiency and aortic stenosis are also not uncommon causes, by over working the heart. The best agent for fatty degeneration is digitalis. Ernest B. Sangree (Med. Brief, June, '96).