The pericardium consists of two layers: the inner visceral layer, which is attached to the epicardium, and an outer parietal layer. The pericardium stabilizes the heart in anatomic position and reduces contact between the heart and surrounding structures. It is composed of fibrous tissue, and although it will permit moderate changes in cardiac size, it cannot stretch rapidly enough to accommodate rapid dilation of the heart or accumulation of fluid without increasing intrapericardial (and, therefore, intracardiac) pressure.

The pericardium is often involved by processes that affect the heart, but it may also be affected by diseases of adjacent tissues and may itself be a primary site of disease.

Inflammatory Pericarditis

Introduction
Acute inflammation of the pericardium may be infectious in origin or may be due to systemic diseases (autoimmune syndromes, uremia), neoplasm, radiation, drug toxicity, hemopericardium, or contiguous inflammatory processes in the myocardium or lung. In many of these conditions, the pathologic process involves both the pericardium and the myocardium.

The presentation and course of inflammatory pericarditis depend on its cause, but all syndromes are often (not always) associated with chest pain, which is usually pleuritic and postural (relieved by sitting). The pain is substernal but may radiate to the neck, shoulders, back, or epigastrium. Dyspnea may also be present. A pericardial friction rub is characteristic, with or without evidence of fluid accumulation or constriction (see below). Fever and leukocytosis are often present. The ECG usually shows generalized ST and T wave changes and may manifest a characteristic progression beginning with diffuse ST elevation, followed by a return to baseline and then to T wave inversion. The chest x-ray may show cardiac enlargement if fluid has collected, as well as signs of related pulmonary disease. The echocardiogram may disclose pericardial effusions and indicate their hemodynamic significance, but it is often normal in inflammatory pericarditis.

Several of the specific pericarditis syndromes are discussed below.

Viral Pericarditis
Viral infections (especially infections with coxsackieviruses and echoviruses but also influenza, Epstein-Barr, varicella, hepatitis, mumps, and HIV viruses) are the commonest cause of acute pericarditis and probably are responsible for many cases classified as idiopathic. Males - usually under age 50 years - are most commonly affected. Pericardial involvement often follows upper respiratory infection. The diagnosis is usually clinical, but rising viral titers in paired sera may be obtained for confirmation. Cardiac enzymes may be slightly elevated, reflecting a myocarditic component. The differential diagnosis is primarily with myocardial infarction.

Treatment is generally symptomatic. Aspirin (650 mg every 3-4 hours) or other nonsteroidal agents (eg, indomethacin, 100-150 mg daily in divided doses) are usually effective. Corticosteroids may be beneficial in unresponsive cases. In general, symptoms subside in several days to weeks. The major early complication is tamponade, which occurs in fewer than 5% of patients. There may be recurrences in the first few weeks or months. Rare patients will continue to experience recurrences chronically, sometimes leading to constrictive pericarditis, when pericardial resection may be required.

Tuberculous Pericarditis
Tuberculous pericarditis has become rare in developed countries but remains common in other areas. It results from direct lymphatic or hematogenous spread; clinical pulmonary involvement may be absent or minor, although associated pleural effusions are common. The presentation tends to be subacute, but nonspecific symptoms (fever, night sweats, fatigue) may be present for days to months. Pericardial effusions are usually small or moderate but may be large. The diagnosis can be inferred if acid-fast bacilli are found elsewhere. The yield of organisms by pericardiocentesis is low; pericardial biopsy has a higher yield but may also be negative, and pericardiectomy may be required. Standard antituberculous drug therapy is usually successful, but constrictive pericarditis can occur.

Other Infectious Pericarditides
Bacterial pericarditis has become rare and usually results from direct extension from pulmonary infections. Symptoms and signs are similar to those of other types of inflammatory pericarditides, but patients appear toxic and are often critically ill. Borrelia burgdorferi, the organism responsible for Lyme disease, can also cause myopericarditis.

Uremic Pericarditis
This syndrome is a common complication of renal failure. The pathogenesis is uncertain; it occurs both with untreated uremia and in otherwise stable dialysis patients. The pericardium is characteristically “shaggy,” and the effusion is hemorrhagic and exudative. Uremic pericarditis can present with or without symptoms; fever is absent. The pericarditis usually resolves with the institution of - or with more aggressive - dialysis. Tamponade is fairly common, and partial pericardiectomy (pericardial window) may be necessary. Whereas anti-inflammatory agents may relieve the pain and fever associated with uremic pericarditis, indomethacin and systemic glucocorticoids do not affect the natural history of uremic pericarditis.

Neoplastic Pericarditis
Spread of adjacent lung cancer as well as invasion by breast cancer, renal cell carcinoma, Hodgkin’s disease, and lymphomas are the commonest neoplastic processes involving the pericardium and have become the most frequent causes of pericardial tamponade in many countries. Often the process is painless, and the presenting symptoms relate to hemodynamic compromise or the primary disease. The diagnosis can usually be made by cytologic examination of the effusion or by biopsy, but it may be difficult to establish clinically if the patient has received mediastinal radiation within the previous year. MRI and CT scan can visualize neighboring tumor when present. The prognosis with neoplastic effusion is dismal, with only a small minority surviving 1 year. If it is compromising the patient, the effusion is initially drained. Instillation of chemotherapeutic agents or tetracycline may also prevent recurrence. Pericardial windows are rarely effective, but partial pericardiectomy from a subxiphoid incision may be successful; patients may be too ill to tolerate this.

Postmyocardial Infarction or Postcardiotomy Pericarditis (Dressler’s Syndrome)
Pericarditis may occur 2-5 days after infarction due to an inflammatory reaction to transmural myocardial necrosis. It usually presents as a recurrence of pain with pleural-pericardial features. A rub is often audible, and repolarization changes may be confused with ischemia. Large effusions are uncommon, and spontaneous resolution usually occurs in a few days. Aspirin or nonsteroidal agents in the dosages given in the section on viral pericarditis provide symptomatic relief.

Dressler’s syndrome occurs weeks to several months after myocardial infarction or open heart surgery, may be recurrent, and probably represents an autoimmune syndrome. Patients present with typical pain, fever, malaise, and leukocytosis. The sedimentation rate is usually high. Large pericardial effusions and accompanying pleural effusions are frequent. Tamponade is rare with Dressler’s syndrome after infarction but not when it occurs postoperatively. Nonsteroidal agents may be given, but recurrences are common; corticosteroids are effective but may be difficult to withdraw without relapse.

Radiation Pericarditis
Radiation can initiate a fibrinous and fibrotic process in the pericardium, presenting as subacute pericarditis or constriction. The clinical onset is usually within the first year but may be delayed for many years. Radiation pericarditis usually follows treatments of more than 4000 cGy delivered to ports including more than 30% of the heart. Symptomatic therapy is the initial approach, but recurrent effusions and constriction often require surgery.

Other Causes of Pericarditis
These include connective tissue diseases, such as lupus erythematosus and rheumatoid arthritis, drug-induced pericarditis (minoxidil, penicillins), and myxedema.

Ross AM et al: Acute pericarditis. Evaluation and treatment of infectious and other causes. Postgrad Med 2004;115:67.

Talreja DR et al: Constrictive pericarditis in 26 patients with histologically normal pericardial thickness. Circulation 2003;108:1852.

Troughton RW et al: Pericarditis. Lancet 2004;363:717.