With pericarditis, “peri” means “around,” card means “the heart”, and itis means “inflamed”. So pericarditis means the pericardial layer of tissue that covers the heart has inflammation. Acute pericarditis generally lasts just a few weeks, whereas chronic pericarditis lasts longer, usually more than 6 months. People who develop pericarditis are also at risk of also developing a pericardial effusion - that’s when the inflammation causes fluid to accumulate around the heart.
The pericardium is a pouch or cavity that the heart sits inside of. The outer layer of this pouch is the fibrous pericardium and it helps keep the heart in place within the chest cavity. The inner layer of the pouch is the serous pericardium that includes the pericardial cavity, and is filled with a small amount of fluid that lets the heart slip around as it beats. The cells of the serous pericardium secrete and reabsorb the fluid, so usually there’s no more than 50 milliliters of fluid in the pericardial cavity at one time - that’s about as much as a shot glass.
Now, the cause of acute pericarditis is usually idiopathic, meaning that we don’t know what causes it. When the cause is identified, it’s usually a viral infection, like Coxsackie B virus. Another cause is Dressler syndrome which occurs several weeks after a myocardial infarction, or heart attack. Basically, when heart cells die in a myocardial infarction, it leads to massive inflammation that also involves the serous pericardium. Another cause of pericarditis, called uremic pericarditis, is when blood levels of urea, a nitrogen waste product, get really high usually due to kidney problems. The high levels of urea irritate the serous pericardium, making it secrete a thick pericardial fluid that’s full of fibrin strands and white blood cells. This gives the wall of the serous pericardium a “buttered bread” appearance.