Diseases of the Pericardium

As explained in chapter 1, the pericardium consists of two layers of a thin membrane, one lining the outside of the heart (visceral pericardium), the other enveloping the heart and the first portions of the great vessels (parietal pericardium). Between the two layers is space for a small amount of fluid acting as a lubricant to reduce friction between them during cardiac motion. An increase in the amount of pericardial fluid (pericardial effusion) occurs in many conditions affecting the heart and other organs. The parietal pericarduim has enough elasticity to accommodate a fair amount of pericardial fluid, so that pericardial effusion ordinarily does not interfere with the function of the heart.

Diseases of the pericardium may have a significant effect on the function of the heart if they restrict its motion. Restriction can

develop if the amount of pericardial fluid exceeds the elastic capacity of the parietal pericardium or if the pericardium thickens and loses its elasticity.

Pericardial tamponade occurs if pericardial fluid accumulates too rapidly to permit adaptive stretching of the pericardium. The pressure in the pericardial sac rises, and when it exceeds that in the atria, the filling of the heart in diastole is interfered with. Tamponade is a serious condition that may become a life-threatening emergency. Though tamponade may develop in the course of acute pericarditis, its most dangerous cause is the escape of blood from the heart into the pericardial sac, a condition known as hemopericardium. The principal cause of naturally occurring hemopericardium is rupture of the heart during acute myocardial infarction. This complication is usually fatal, although occasionally there is enough time to perform immediate corrective surgery. The commonest cause of pericardial tamponade due to hemopericardium is trauma resulting from one of the many diagnostic or therapeutic intracardiac interventions and, rarely, from cardiac surgery. Tamponade may also develop because of external trauma—stab wounds or gunshot wounds.

The immediate consequence of tamponade is a fall in arterial blood pressure and an increase in venous pressure. When arterial pressure reaches shock level, tamponade becomes a life-threatening emergency and must be recognized immediately. Instant relief follows removal of blood or fluid from the pericardium by means of a needle inserted through the skin and the chest wall into the pericardial sac. It is sometimes necessary to supplement this treatment with surgical drainage of the pericardium.

Acute pericarditis is most often caused by viral infection either as a part of general infection with a virus or as a disease limited to the pericardium. It is usually a self-limiting febrile illness lasting one to two weeks and almost never has immediate aftereffects. The principal feature of acute pericarditis is chest pain, which may resemble the ischemic pain of coronary-artery disease. In rare cases fluid accumulation may be rapid enough to produce tamponade. The diagnosis of pericarditis is commonly made on the basis of characteristic abnormalities in the electrocardiogram. However, the most sensitive and reliable means of demonstrating pericardial fluid is echocardiography.

Acute pericarditis is treated with antiinflammatory drugs to control the pain. Although acute pericarditis is often referred to as benign, in a small number of cases there are late consequences. One or more attacks of recurrent pericarditis may develop at intervals of a few weeks. Late appearance of constrictive pericarditis (see below) may take place particularly in patients who have had more than one attack.

Acute pericarditis similar to the viral variety often develops from one of the systemic diseases characterized by an allergic-type reaction. These diseases include rheumatic fever, systemic lupus erythematosus, and rheumatoid arthritis. Pericarditis can also occur after acute myocardial infarction (Dressler syndrome) and occasionally after cardiac surgery (postcardiotomy syndrome). These attacks are particularly prone to recur periodically.

Chronic pericardial effusion may develop with or without disease of the pericardium. Increased fluid in the pericardial sac is common in cases of general fluid retention due to cardiac or renal disease. As such it produces no symptoms and may be discovered by chest X ray (marked enlargement of the cardiac shadow) or echocardiography. When pericardial disease is present, persistence of fluid is often a precursor of constrictive pericarditis. Tuberculous pericarditis is characterized by pericardial effusion persisting for years and gradually leading to thickening of the pericardium and pericardial constriction, with eventual disappearance of the fluid. Uremic pericarditis is a common complication of chromic kidney failure; tamponade and, rarely, constrictive pericarditis may result. Neoplastic pericarditis may be caused by primary tumors (neoplasms) of the pericarduim or by invasion of tumors from elsewhere, particularly the lungs. Postradiation pericarditis may develop in patients after radiotherapy for cancer in the chest, including breast cancer.

Echocardiography is the principal diagnostic tool in pericardial effusion. Frequently a pericardial needle tap (to remove fluid) is needed to determine the nature of the effusion, particularly if tuberculosis or neoplasm is suspected. Surgical drainage or removal of parts of the pericardium may be indicated even in the absence of fully developed constrictive pericarditis.

Chronic constrictive pericarditis is present when a diseased pericardium becomes so thick and stiff that the filling of the heart is

interfered with. The two layers of the pericardium often adhere to each other, forming a firm, inelastic structure in which the heart is encased. In late stages of constrictive pericarditis calcium deposits may envelop the heart in a bonelike armor. Constrictive pericarditis often resembles congestive heart failure. But because of its chronicity massive edema and enlargement of the liver, which may result in secondary cirrhosis of the liver, are much more common than in congestive heart failure.

At one time, most cases of constrictive pericarditis were caused by tuberculosis, which today is rare. Now constriction may be the end result of acute pericarditis and may sometimes be found in cases of uremic pericarditis and neoplastic pericarditis. It is also a complication of radiation therapy for cancer of the breast or other structures in the chest. The diagnosis of constrictive pericarditis can often be made on the basis of physical examination and X rays. Echocardiography is helpful but may not be as decisive as in pericardial effusion. As mentioned, it is occasionally difficult to distinguish constrictive pericarditis from restrictive cardiomyopathy. Treatment is primarily surgical, although in early stages diuretics can provide considerable relief of symptoms. Surgical removal of the thick pericardium does not require that the heart be opened; nevertheless, the risk in surgery is moderately high.

Purulent pericarditis involves the accumulation of pus in the pericardial space. It frequently is a complication of a purulent process in the chest. This type of pericarditis usually requires prolonged surgical drainage.