Acute pericarditis resulting from acute articular rheumatism has some peculiarities which it is well to bear in mind. It comes on early in the disease. We also know of its great frequency as a result of rheumatism, although the rheumatism be mild; for the intensity of the rheumatic inflammation is no measure of the extent or severity of the pericarditis. Nor does the number of joints involved nor their location give any idea of the greater or lesser liability of the pericardium to participate in the inflammatory action. Neither does the frequency of the rheumatic attacks bear any direct relation to the pericardial involvement; although experience has shown that the first attack usually is the one most likely to be the cause of pericarditis, while succeeding ones may or may not produce fresh seizures of pericarditis, or an aggravation of the disease where it has remained as the result of previous attacks of rheumatism.
Clinical literature is notably deficient in the reports of pericarditis ending in recovery, while the recorded cases of death from the disease as verified by autopsies are most numerous. Yet, although pericarditis is a serious malady, it is not commonly fatal; and this is especially true of the pericarditis of acute rheumatism. But it is a frequent disorder. Sibson,4 with large experience and patient observation, has collected and tabulated facts from many sources. In that particular variety of pericarditis which is the accompaniment of acute articular rheumatism he found that in 326 cases of acute rheumatism admitted into St. Mary's Hospital, about one-fifth of the cases (63) had pericarditis, which was accompanied in 54 cases by endocarditis; and only in one-fourth of the whole number (79) was there neither pericarditis nor endocarditis. One-third of the whole number of cases (108) had endocarditis, and a fourth (76) had threatened endocarditis, the signs being transient or imperfect. It is notable that the majority of the cases, regardless of sex and occupation, occurred prior to the twenty-fifth year of age; and what is equally notable is that the severity both of the joint and the heart affections was greatest at or before the same year. Of the 63 cases of pericarditis in rheumatism, there were 35 males and 18 females; of these, 11 males and 14 females were from sixteen to twenty years of age, and the fatal cases were all under the twentieth year.
4 Reynolds's System of Medicine, vol. iv.
Pericarditis happens most frequently between the first and second weeks of acute rheumatism, although there are instances in which it occurs later, and occasionally it follows a sudden subsidence of the disease. It may be observed coincident with the onset of the rheumatic attack, and even preceding it by several hours. Latham has pointed out how acute pericarditis is more to be looked for when acute rheumatism is shifting and inconstant in its seat than when it is fixed and abiding.
Having now looked at rheumatic pericarditis, we may examine the pericarditis of some other disorders. In that class of affections known as Bright's disease of the kidney the serous membranes are liable to take on inflammatory action. A particular preference for the pericardium seems to exist, and the affections are the cause of pericarditis next in frequency to acute rheumatism. The tendency varies, however, with the particular kind of disease of the kidney which may be present. Pericarditis is common in the contracted kidney; in amyloid degeneration it is rare.5 Where uræmia happens, it is apt to be developed. In warm climates it is less usual as an accompaniment than it is in cold and damp. But whether this be the full explanation of the varying frequency of pericarditis as an attendant upon Bright's disease in different countries is doubtful. There is, however, certainly, as we learn from the elaborate inquiry of Sibson, a varying ratio. The complication is, he proves, more frequent in Germany than in England, least frequent in France.
5 Ziemssen's Cyclopædia, vol. xv. p. 629.
Let us now take into consideration other diseases which in their course have strong, although less-marked, tendencies to involve the pericardium. As a class, the eruptive fevers, especially scarlet fever, may present a pericardial lesion. This is owing to the fact that the serous membranes generally are liable to become inflamed in these conditions; but another element in the production of acute pericarditis may probably be found in the congestion of the kidneys which is apt to occur. Pericarditis is not commonly present early in these diseases, but rather in their later stages, when the body is enfeebled by the specific poison and the skin is susceptible to the slightest variation of temperature. It is then that the weakest and most vulnerable part will be attacked, and the pericardium may prove to be the most vulnerable part.
Other diseases which will cause pericarditis are those dependent upon dyscrasia of the blood, as in the diatheses, injuries attended by shock, and those conditions in which there is a great drain from the system. Perhaps the diathesis most apt to induce pericardial inflammation is the scorbutic, in which the impoverished and relaxed state of the system frequently manifests itself by inflammatory lesions of a low grade. In injuries or diseases where there is excessive suppuration the system is so weakened that a low form of pericarditis is prone to develop itself. Diseases of the respiratory organs, as phthisis, pneumonia, or pleurisy, also enteric inflammations, will sometimes produce pericarditis. Indeed, any disease dependent upon or attended by a greatly deteriorated condition of the blood may cause pericarditis; for the health of the heart itself is determined by the quality of the vital fluid from which it draws its own sustenance in common with all other structures of the body, and any vitiated state of the blood seems to make a special impression upon the heart itself, its membranes as well as its structure.
MORBID ANATOMY.—In acute pericarditis the serous membrane first becomes injected with blood, and the injection, starting at a single or at several points, may become diffuse. If the engorged vessels do not relieve themselves, infiltration of lymph into the transparent serous layer follows, producing thickening and opacity as well as slight roughness. Consequent upon this there is further congestion, the membrane becomes red, with possibly here and there points of inflammation of greater intensity than that surrounding the original lesion; and at these places the vessels may give way and cause a hemorrhage into the sac or there are little spots of ecchymosis in the membrane. Usually there is a drying up or a partial suspension of the serous secretion from the turgid membrane, but before long the secretion generally recurs, and is even increased in quantity. Upon the surface of the serous membrane patches of coagulable lymph, more or less extended, are at the same time exuded. Under the microscope the bundle of fibres of connective tissue of the membrane appear swollen and broken up, and the proliferation starts which, as it progresses, determines the new growth and the villosities. Portions of the exuded lymph may be washed off and be found as shreds in the serum. The appearance of the lymphous deposit, as just indicated, is not always that of a plain smooth layer, but may be velvety and villous, like the lining of the small intestine, or it may be more roughened, or it may be honeycombed, as the interior of the stomach of the calf, or be in ragged shreds of varying sizes, either single or in bunches. Again, it may assume a lace-like texture, as of fibres coarsely woven together, or it may appear as if the threads were attached at one end to the pericardium and at the other floating free. All of these various forms are largely due to the heart, which in its action presses and rubs the lymph-covered surfaces together and keeps the softish exudation in constant agitation. One layer of lymph may be superimposed upon another until the deposit becomes very thick. It is this lymph which, existing before fluid is effused to any extent, determines what clinicians recognize as the dry or plastic stage of pericarditis.
Generally, however, there is effusion of considerable liquid, occasioning what is termed the stage of effusion. The fluid poured out is serous, alkaline, and albuminous, of a pale-yellow color, and transparent, but it may be opaque and milky. It may have flocculi floating in it, be stained any shade of color from red to brown by the coloring matter of the blood or by exuded blood-corpuscles, and may also contain pus. The quantity of fluid varies from a few ounces to several pints, but the latter amount is rare. The fluid is usually composed of the watery and saline elements of the blood, with a small quantity of albumen and a trace of fibrin. If the amount of fluid be small, the opposing surfaces of the pericardium come together, and the lymphous layer, becoming more or less organized by the presence of blood-vessels in it, makes attachments to the opposite wall; in this manner adherent pericardium is produced. The adhesion may vary in extent from the slightest filamentous attachment to complete obliteration of the pericardial sac; and it may be readily peeled off, or it may be so closely united as to become a part of the tissue upon which it lies. As the disease progresses the serum and, in exceptional cases, the fibrinous deposits may be entirely reabsorbed and leave but little evidence of the previous inflammation. The white milky-looking spots often found in autopsies are regarded by many as the remains of cured pericarditis, but they are more likely the result of nutritive changes and consequent tissue-alteration. Fibrinous deposits are not always entirely removed. In complete adhesion of the pericardium they may be considerably reduced, but the sac never regains its normal appearance, and when the adhesions are partial they remain permanently.