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Endocarditis - Rheumatism

friction, valve, inflammation, lining, valves and contact

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ENDOCARDITIS - RHEUMATISM.

By the endocardium the anatomist means the thin transparent membrane which lines the interior of the cavities of the heart, is re flected over its valves and muscular folds, is continuous on the left side with the lining membranes of the aorta and of the pulmonary veins, and ou the right with those of the pulmonary artery and sys temic veins.

The clinical observer attaches to the term a wider meaning, and includes under it all the structures which lie inside the heart—the fibrous rings and valves as well as the lining membrane. It is of im portance that this distinction should be borne in mind, for we shall presently see that the endocardium of the anatomist, the lining mem brane of the heart properly so-called, is never the primary seat of rheumatic inflammation. We now use the term in its wider sense. By endocarditis we mean inflammation of any or all of the non-mus cular structures situated inside the heart—the fibrous texture of the rings and valves as well as the lining membrane.

Rheumatic inflammation never affects the whole surface of the lining membrane of the heart; it is limited to the part which is re flected over the valves ; and when other parts suffer the mischief is almost invariably attributable to mechanical injury produced by the rubbing on the affected portion of the endocardial surface of an al ready damaged valvular segment. Moreover, the inflammation does not affect the whole valvular surface ; only one side of a segment suffers—that, namely, which comes in contact with another segment in the act of closure—in the aortic valve its convex surface, and in the mitral its auricular. The damage is further limited in its early stage to the line at which the segments come into contact.

The limitation of the disease to this particular part of the valve has been attributed to the fact that it is the part which is most ex posed to friction. "In its earliest stages it always occurs near the edges of a valve in the formation of a line of little elevations along the contact line of its segments, where the friction is greatest" (Wilks and Moxon).

"It is those portions of the valve which come into contact in the act of closure and are thus most exposed to friction, which are es pecially involved, and in which the changes usually commence" (T. Henry Green).

That friction may produce inflammation of the lining membrane of the heart there can be no doubt. Occurring in other than its valvular portion it is almost always due to the rubbing on its surface of a damaged valve. Knowing this to be the case, and finding that inflammation of its valvular portion commences at the line of contact of the different segments of the valves, and therefore at the point at which, if anywhere, they must rub, we cannot fail to see that there is good reason for the belief that friction plays an important part in the production of the inflammation of the lining membrane of the heart's cavities which is found in connection with acute rheumatism. Were this lesion the direct result of the action of the rheumatic poison it would not be limited to one side of the valve ; it would affect both. Furthermore, its invariable limitation to the points at which the valvular segments come in contact shows that the cause which gives rise to it is something which comes into play only at that point. Friction is the most probable if not the only possible cause, and as the seat of the lesion is also the only point at which friction can come into play, the conclusion is forced upon us that friction is the direct cause of the lesion.

But the question arises—Why is there friction? Why do the segments of the valves rub against each other? When a valve is al ready damaged or roughened, it is easy to see how further damage may be clone; but in a smooth, uninjured valve how is the mischief set agoing? It cannot be that the valves constantly and and naturally rub against each other—for in that case, if friction produced endo carditis, no one would be free from it; rheumatic and non-rheumatic subjects would equally suffer, and a smooth, healthy valve would be the exception.

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