Pericardium, a conical membranous sac containing the heart and the commencement of the great vessels, to the extent of about 2 inches from their origin. It is placed with its apex upwards behind the sternum in the interval between the pleurae—the serous sacs in which the lungs are enclosed; while its base is attached to the diaphragm. It is a fibro-serous membrane, consisting of an external fibrous and an internal serous layer. The outer layer is a strong, dense, fibrous membrane; the serous layer invests the heart, and is then reflected on the inner surface of the fibrous layer. Like all serous membranes, it is a closed sac; its inner surface is smooth and glistening, and secretes a thin fluid which serves to facilitate the natural movements of the heart. It is inflammation of this serous sac which constitutes the disease known as pericarditis.
DISEASES OF THE PERICARDIUM.—Pericarditis is a disease of frequent occurrence; the result of a very large number of post-mortem examinations being to show that about one in twenty-three of all who die at an adult age exhibits traces of recent or old attacks of this disorder. The first change which takes place in an inflamed pericardium is a dulling of its glistening surface, with some congestion, which is speedily followed by effusion into the sac. The effusion is sometimes almost entirely fibrinous, in which case it coagulates, and gives rise to adhesions between the heart and the pericardium; or it may consist almost entirely of serum, which remains liquid; or it may be, and most frequently is, a mixture of the two. In a few cases it rapidly becomes purulent. In the cases that prove fatal when fibrinous fluid has been effused, but has not coagulated to such an extent as to cause complete adhesion of the heart to the pericardium, the partially coagulated fibrin or lymph is seen to be of a yellowish-white colour, and to occur in a rugged, shaggy, or cellular form. Laennec compared the surface on which the lymph is deposited to that which would be produced by suddenly separating two flat pieces of wood between which a thin layer of butter had been compressed. When the patient dies at a more advanced stage of the disease—viz. soon after the whole of the membrane has become adherent—incipient blood-vessels, in the form of red points and branching lines, are seen, indicating that organisation is commencing in the deposit, which if death had not ensued would have been finally converted into cellular or areolar tissue, and might have occasioned the complete obliteration of the pericardial cavity.
The recognition of the disease depends almost entirely upon the signs revealed by auscultation and percussion. The earliest is generally the friction-sound, or to and fro murmur, caused by rubbing together of the roughened surfaces, and heard to accompany the heart's action; but if fluid is effused it may speedily disappear. In this case percussion of the chest shows that the dull area occupied by the heart is larger than normal, while the impulse of the organ on the chest-wall cannot be felt. The symptoms, besides those common to all inflammations, are extremely variable: in some cases where pericarditis comes on in the course of other serious disease the patient makes no complaint, and the complication is only discovered during the routine examination of the chest. But there may be intense pain and tenderness on pressure in the region of the heart, great irregularity or feebleness of the heart's action, distressing breathlessness, delirium, &c.
Pericarditis is a disease which occasionally runs a very rapid course, and terminates fatally in forty-eight hours or less. In ordinary cases, however, which terminate in apparent recovery, the disease generally begins to yield in a week or ten days, and, excepting that adhesion may remain, the cure appears to be complete in three weeks or less. If the adhesions which have formed are dense and fibrous, they may impede the heart's action and lead to serious symptoms at some subsequent period.
Pericarditis rarely occurs as an independent disease. It may result from extension of an inflammation in a neighbouring organ, pleura, ribs, &c. It is no uncommon result of a contaminated state of the blood, such as occurs in the exanthematous diseases, especially scarlatina, and in Bright's disease of the kidney; but, beyond all comparison, it is of most frequent occurrence in association with acute Rheumatism (q.v.), of which it forms one of the most serious complications. It is often associated with inflammation of the muscular substance of the heart, and, especially in rheumatism, of the lining membrane as well.
The treatment of pericarditis at present in favour is much less active than when bleeding, mercurialisation, &c. were considered necessary. Complete rest in bed, light diet, with opium or other sedatives as required; general medication suited to the disease with which the pericarditis is associated; local application of poultices or cotton-wool, sometimes of leeches or blisters, are the chief measures employed. In cases where there is extensive fluid effusion it may be necessary to aspirate, or, if the fluid be purulent, even to make a free incision.
The pericardium may also be distended with fluid without inflammation (hydropericardium) in the course of general dropsy; and occasionally is the seat of tumours, syphilitic or tubercular processes, &c.