Acute Pericarditis

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.