A system of practical medicine. By American authors. Vol. 3

by Unknown

A rupture of the mitral valves will open into the auricular, and that of the aortic into the ventricular, cavity. The reason for this is to be found in the fact that when the valves are closed the blood-pressure is exerted from the left ventricle toward the mitral valve, and from the aorta toward the semilunar valves. If the blood penetrates a rent in a flap of the valves, the endocardium is puffed out, and a valvular aneurism is formed, and round or funnel-shaped aneurismal sacs may project from the valves. The bottom of one of these sacs may be perforated, and long, ragged, gray shreds, covered with fibrin, may be found hanging in the ventricular cavity.

Microscopically, the torn shreds from a valvular aneurism, the result of acute endocarditis, consist of nuclei and round cells imbedded in a mass of granular matter. There is neither connective fibrilla nor elastic tissue. When the ulceration is localized in the ventricle, the pressure of the blood may bulge out the heart-wall, and thus give rise to a so-called partial cardiac aneurism. By rupture of such aneurism communication between the different heart-cavities may be established, which will vary with the seat of the ulceration.

Acute exudative endocarditis may involve the muscular structure of the heart. Such myocarditis (or carditis) may involve the deeper structures, weaken them, and so alter their consistence that bulging and the formation of a ventricular aneurism may result. Usually such myocarditis is so slight that incomplete organization of the new embryo-plastic cells occurs and the tissue undergoes fatty changes. The results of all forms of acute endocarditis are best studied in connection with the morbid changes of interstitial endocarditis, into which they so often gradually merge.

Interstitial Endocarditis.

MORBID ANATOMY.—Interstitial (or chronic) endocarditis may be a continuation of a process which commenced in an acute exudative endocarditis, or it may be interstitial from its commencement, and be so insidiously evolved as to escape notice. The anatomical changes may sometimes be confined to the edges of the valves, at others to their base, or they may involve the entire valves, which become thickened, indurated, contracted, degenerated, and adherent. It is more closely allied to rheumatism, gout, and chronic interstitial changes in other organs than either of the other varieties.

There is no part of the endocardium which is exempt from interstitial inflammation. The favorite place for its development is the endocardium of the valves and that at the apex of the left ventricle. The thickening at first may be either translucent or opaque, and the valves may become three or four times thicker than normal. In some instances, although the valves are thickened and indurated, their functional activity is not interfered with, and they offer no obstruction to the blood-current.

White, thickened, opaque spots are often irregularly scattered over the internal wall of the heart. The vegetations met with in interstitial endocarditis differ from those of the acute exudative variety in that they are less prominent and firmer. They rest upon an indurated base. Their cartilaginous consistency is due to the fact that their cellular elements are not round (as in acute exudative endocarditis), but elongated and flattened, possessing an abundant intercellular fibrillated tissue.

In and underneath the endocardium there is an increase of tissue, and upon any prominence arising from the thickening of the endocardium occur fibrin deposits. These fibrinous efflorescences assume a variety of forms, and sometimes string out into the adjacent vessels and cavities for half an inch or more. Their usual form is globular or wart-like, and their seat is on the ventricular surface of the aortic and upon the auricular surface of the mitral and tricuspid valves.

In interstitial endocarditis the cell-development is far less rapid and abundant than in the acute exudative form, and this very slowness accounts for the greater induration and thickening.

A microscopical examination of a cross-section of an indurated valve shows a number of flat cells arranged in irregular layers, having between them a fibrinous material which has in it here and there a few elastic fibres. The new formations always originate in the layer of flat cells. These changes are best marked in the fibrous zone at the valvular orifices, upon the surfaces of the valves themselves, and in the chordæ tendineæ. The new tissue, whether developed rapidly as in acute exudative, or slowly as in interstitial endocarditis, becomes fibroid and contracts, and this contraction is progressive.