Pericarditis is a swelling and irritation of the pericardium, which is the sac that surrounds your heart.

Most of the time the cause is either not known or is thought to be a viral infection.

Less common causes of pericarditis are a heart attack, a bacterial infection, an injury to the chest, or radiation treatments for cancer. Kidney failure, HIV infection, tuberculosis, hypothyroidism, autoimmune diseases such as lupus, or certain drugs may also cause pericarditis.