Pericarditis
Pericarditis is swelling of the pericardium, which is the fluid-filled sac that surrounds your heart.
The most common symptom of acute pericarditis is chest pain which is worse when lying down.
It's not always clear what causes pericarditis, although a viral infection is usually suspected.
The first stage in the diagnosis of pericarditis is to ask about your symptoms and recent medical history.
Pericarditis is usually treated with medication, although surgery is used in rare cases.
In rare cases, pericarditis can develop into further problems, some of which can be life-threatening.