Swelling and irritation of the thin, saclike tissue that surrounds the heart, called the pericardium.

Pericarditis has various causes. These include an immune system response after a heart attack, viral infections, chest injuries and conditions such as lupus. Sometimes the cause isn't known.

The most common symptom is sharp, stabbing chest pain. It may travel to the left shoulder and neck. Other symptoms can include fatigue, cough, fever, shortness of breath, and a fast or pounding heartbeat.

For mild pericarditis, rest and pain medicines sold without a prescription may be the only treatment needed. If the condition is serious, treatment can include prescription medicines and, rarely, surgery.