pericarditis
Pericarditis is inflammation of the pericardium, the sac around the heart. When those normally slippery surfaces become irritated and inflamed, they rub instead of glide, producing a characteristic sharp chest pain. Imagine two sheets of waxed paper that have dried out and now scrape against each other every time they move.
The classic pain is sharp and worse when lying flat or breathing in, and it often eases when the person sits up and leans forward. Doctors look for a triad of clues: this positional chest pain, a scratchy pericardial friction rub heard with the stethoscope, and typical electrocardiogram changes such as widespread ST-segment elevation. A small pericardial effusion may also appear on echocardiography.
Many cases are viral or have no identified cause (idiopathic) and settle with anti-inflammatory medicines such as high-dose nonsteroidal drugs plus colchicine. Other causes include bacterial infection, tuberculosis, autoimmune disease, kidney failure, cancer, and the aftermath of heart surgery or a heart attack. Most acute viral or idiopathic episodes resolve well, though a minority recur.
A 30-year-old has a week of flu-like illness, then sharp chest pain that eases when he leans forward; a friction rub is heard and the ECG shows widespread ST elevation. He is diagnosed with acute viral pericarditis and improves on ibuprofen and colchicine.
A textbook presentation of acute pericarditis: positional pain, friction rub, and diffuse ST elevation.
Pericarditis chest pain can mimic a heart attack, but the two are distinguished by the pain's positional nature, the friction rub, and the diffuse rather than territorial ST changes on the electrocardiogram.