Pericarditis is an inflammation of the pericardium, the thin, fluid-filled sac surrounding the heart. Most patients who have pericarditis also suffer from fluid buildup in the pericardial sac, a condition known as pericardial effusion. If severe, pericardial effusion may be a medical emergency because the fluid in the pericardial sac  puts dangerous pressure on the heart and on a portion of the heart’s major blood vessels. If fluid buildup is fast and heavy enough, it could result in a rare but dangerous condition known as cardiac tamponade, in which the pressure on the heart is so great that it cannot pump enough oxygen-rich blood to the rest of the body.

Pericarditis may be acute (sharp and temporary) or chronic (persistent and recurring). Chronic inflammation can cause the pericardial sac to lose some elasticity, scar and perhaps even adhere to the heart. Consequently, the chambers cannot fully fill with blood. This complication is known as constrictive pericarditis. Constrictive pericarditis can potentially lead to right-sided heart failure.

Though pericarditis often has no known cause (idiopathic pericarditis), there are a number of factors that can influence its development, including:

Other conditions associated with pericarditis include:

• Myocarditis.
  
  
• Kidney failure, leading to uremia (uremic pericarditis).
  
  
• Lupus erythematosus.
  
  
• Cancer (neoplastic pericarditis).
  
  
• Rheumatoid arthritis.
  
  
• Systemic lupus erythematosus.
  
  
• Scleroderma.
  
  
• Chest trauma (due to injury, surgery or radiation therapy).
  
  
• Certain medications.
  
  
• Rheumatic fever. This potentially serious complication of streptococcal (“strep”) infections can result in the inflammation of the myocardium (the heart muscle), the endocardium (the inner lining of the heart’s pumping chambers) or the pericardial sac.
  
  
• Bacterial infection. Bacterial pericarditis (sometimes called purulent pericarditis)  is caused by bacteria such as pneumococcus, strep or staphylococcus. Since the advent of antibiotics, bacterial pericarditis has become relatively rare.
  
  
• Hereditary factors (familial pericarditis).
  
  
• Smallpox vaccine. In rare cases, this vaccine can cause pericarditis.

Younger adults diagnosed with pericarditis are more likely to have pericarditis due to viral infection or unknown causes, whereas older adults generally suffer from trauma-based or cancer-linked causes. Men between the ages of 20 and 50 are most likely to develop pericarditis. Overall, about one in 1,000 patients admitted to the hospital are diagnosed with this condition, although it is believed that many more individuals have a mild form that is never positively diagnosed.