Ask the doctor: What is pericarditis?

Q. I had chest pains for a couple of days and thought I was having a heart attack. My doctor did an electrocardiogram and said I had pericarditis and that it was not serious. What exactly is pericarditis?

A. Pericarditis is inflammation of the pericardium, a protective, double-layered sac surrounding the heart. It has many different possible causes, including a virus or other infection, certain illnesses, an injury to the chest, radiation therapy for cancer, or a reaction to medications. Complications from bypass surgery or the insertion of a pacemaker are other possible triggers. But most of the time, the cause remains elusive.