Inflammation of the pericardium may occur under a variety of circumstances, sometimes in connection with rheumatism, strangles, and influenza, or any low form of fever or specific blood disease. It may also arise from injury, such as a wound inflicted from without, or from the passage of some foreign body from the digestive organs, through the diaphragm into the pericardial sac. This cause is comparatively frequent in cattle, but is extremely rare in the horse. One case is recorded in which a sewing-needle had passed through the oesophagus into the pericardium, and subsequently reached the right auricle of the heart.
As in other cases of disease connected with the central circulatory organ, pericarditis, especially the chronic form, may exist for a considerable period without any symptoms being present which would lead to the suspicion of its existence. This is particularly the case in reference to what is called traumatic pericarditis in cattle. These animals, when at pasture, frequently swallow various extraneous substances which come in their way, and among foreign cattle kept by small owners, and fed very much about the dwelling-houses, it used to be extremely common to find in the rumen of the animals, which were sent to this country for slaughter, various domestic articles, such as brushes, tin or other toys, hair-pins, shawl-pins, skewers, knitting-needles, and even portions of wearing apparel.
In post-mortem examination it frequently happens that a needle, or piece of wire, or a skewer, is detected in the heart sac, and its path can be traced through the second stomach (reticulum), which lies close to the diaphragm, and from that organ into the pericardial sac, and sometimes into the muscular structure of the heart. In other cases, where the body which has inflicted the injury has been lost in the course of the examination, the path which it has taken can be distinctly followed from the second stomach into the heart sac. This condition of things has not uncommonly been observed in animals in good condition sent to the slaughterhouse without any suspicion arising that they were subjects of such severe injuries.
The symptoms of pericarditis of the acute form are very often complicated with those of ordinary inflammation of the lungs and pleura (pleuro-pneumonia), and indeed, in fatal cases of the latter disease, it is quite usual to find indications of inflamed pericardium.
In such cases as the above there would, of course, be great difficulty in separating the symptoms belonging to each set of organs, but it is generally allowed that the character of the pulse, the irregularity of the heart's action, and the presence of a venous pulse in the jugular vein may be taken as indications that the heart sac is implicated in the inflammatory condition.
In pericarditis resulting from injury it is certainly the case that the disease may advance to a considerable extent before any symptoms of illness are apparent; in some cases there may be no particular signs of derangement until the foreign body, needle or skewer, reaches the heart. It has been noticed at the termination of these cases, when the fact of the existence of the disease has been made patent by a post-mortem examination, that the animals for some time before death have been subject to frequent attacks of indigestion, associated with elimination of gas into the rumen in the case of cattle, and into the single stomach of the horse. As a result of the disease, a quantity of fluid, clear or turbid, is usually found in its cavity, with adhesion of a portion of the membrane perhaps to the heart, and sometimes considerable thickening of the structures.
Pericarditis which is independent of the passage of any foreign body or other injury is distinguished as idiopathic, a form which seldom occurs unless in combination with pleuro-pneumonia, and, as previously stated, it is scarcely likely that it would be distinguished at once as a distinct disease in the presence of inflammation of the lungs and pleural membrane. In the event, however, of any suspicion being excited which would lead to an examination of the heart by the application of the ear to the left side, over the cardiac region, it would be discovered that the normal sounds of the heart are less distinct, and if fibrinous exudation has taken place between the two layers of the pericardium, friction sounds might be detected in the early stages of the disease.
Treatment of the idiopathic form of pericarditis may be attempted with some hope of success. It would include the administration of a saline aperient, and in some instances, when the symptoms are very marked, and the heart is affected with palpitations, digitalis is recommended. Fomentations, or the hot pack, or counter irritation to the region of the heart, may also be employed. The body should be well clothed and the legs bandaged, while the strictest quietude should be insisted on.