Pericarditis is inflammation of the pericardium, the fibroserous sac surrounding the heart, and is a common cause of acute chest pain that nurses must distinguish from myocardial infarction. Acute pericarditis develops when inflammatory cells infiltrate the pericardial layers, producing friction between the visceral and parietal pericardium, pain, and often a measurable pericardial effusion. It is clinically significant because it mimics ischemic chest pain yet is treated very differently, and because unrecognized progression can lead to pericardial effusion and life-threatening cardiac tamponade. Common causes: - Idiopathic or viral (most common in developed countries; often preceded by an upper respiratory or GI illness) - Post-myocardial infarction (early peri-infarction pericarditis or delayed Dressler syndrome, weeks after MI) - Post-cardiac surgery or cardiac procedure (post-pericardiotomy syndrome) - Uremia (renal failure; treated with dialysis rather than typical anti-inflammatory therapy) - Autoimmune/connective tissue disease (lupus, rheumatoid arthritis) - Malignancy (metastatic disease, radiation-induced) - Bacterial or tuberculous infection (less common, higher risk of effusion and constriction)