Definition:—An inflammation of the muscular structure of the heart.
The name acute parenchymatous myocarditis may be said to refer to an inflammation involving the parenchymatous muscular fibrillae, while the term interstitial myocarditis designates an inflammation involving the connective tissues within the structure of the heart walls. This may be diffuse, involving the structure of all or the larger part of the heart, or it may be circumscribed, involving a limited area with degenerative changes and abscess. There may be two or more circumscribed areas involved at the same time. Myocarditis occurs secondarily to some other acute involvement. A primary inflammation of this structure alone has not been recognized.
Etiology:—Acute rheumatic inflammation of the endocardium, or of the pericardium, is the most frequent cause of acute inflammation, both of the parenchymatous and interstitial forms. The disease may also result from an extension of endocarditis or pericarditis, from any primary cause. In endocarditis the vegetations which form on the valves give off particles, which enter the coronary arteries and form emboli, plugging the smaller branches and thus resulting in localized infection and destruction of tissue and ultimate abscesses—a circumscribed interstitial myocarditis.
Symptomatology:—While a profound impression may be made upon the condition of the patient by an involvement of the entire structure of the heart in acute inflammation the local symptoms are usually not sufficient to distinguish the involvement from an acute endocarditis or pericarditis, especially if of the ulcerative type. If a large embolus should enter the coronary artery, death would soon follow. The plainly apparent constitutional symptoms depend upon sudden weakness of the heart muscle, which is shown in abrupt and severe cases by a very rapid, feeble, small, easily compressible pulse, which, while at first regular, soon becomes irregular and intermittent. The patient becomes at first very pale, but soon the face assumes a peculiar hue from venous stasis, and vomiting and syncope follow. The respiration is apt to be shallow and rapid, rather than slow and labored. In cases of less rapid development, or those narrowly circumscribed, the symptoms resemble those of ulcerative endocarditis, or those of simple or sub-acute endocardial inflammation, and the patient may continue about his employment to a limited extent with the evidences of severe heart disease and an occasional attack of angina. Physical examination will reveal a tumultuous heart, with valvular murmurs. It will be observed that the two sounds of the heart have become nearly equal, the usual distinction being abolished. There is progressive feebleness of the heart's action, with corresponding circulatory disturbance.
Prognosis:—Complete recovery never occurs after myocarditis. The diffuse and insterstitial forms may result in death in a very short time. The circumscribed form may exist for a considerable length of time, the patient remaining in feeble health. An embolus, from either form, may produce death with but few if any premonitory symptoms.
Treatment:—So similar are the conditions and evidences to those of a severe form of endocarditis that no difference need be recognized in the treatment. Remedies irritating to the heart muscle, as digitalis and strophanthus, must be avoided, and those which nourish these structures should be prescribed. Prescribe in strict accordance with the specific indications and treat the serious general conditions with a full appreciation of their seriousness.
The Eclectic Practice of Medicine with especial reference to The Treatment of Disease, 1910, was written by Finley Ellingwood, M.D.