The pericardium serves to protect the heart from physiologic changes in intracardiac pressure related to respiration and postural change, and it may also augment the mechanical function of the cardiac chambers. The pericardium is composed of a visceral layer that directly adheres to the epicardium and a parietal layer separated by 10 to 35 mL of serous fluid.
Epidemiology and etiologic agents
Both infectious and noninfectious processes have been identified as causes of pericarditis (inflammation of the pericardium). Most cases are due to viral pathogens, are self-limited, and the specific pathogen remains unidentified. Purulent pericarditis due to bacterial or fungal pathogens is less common and the incidence is much lower than during the pre-antibiotic era. In one recent series, pericarditis was diagnosed in 5% of adults presenting for emergency care due to chest pain that was not associated with myocardial infarction. Most episodes of pericarditis occur in the spring and summer coincident with the peak prevalence of enteroviruses. During the winter months, influenza virus is a frequent cause of pericarditis, whereas pericarditis due to bacterial or atypical pathogens occurs throughout the year. There are no clinical features which allow the differentiation between viral and idiopathic causes of acute pericarditis.