It depends on its severity and cause. Small ones that don’t have symptoms and are due to known causes require no special treatment.
For pericardial effusions due to inflammation of the sac, treating the inflammation also treats the effusion.
In that case, you may be given:
Nonsteroidal anti-inflammatory drugs (NSAIDs), like Aleve, Indocin, and Motrin
Corticosteroids, like prednisone and Solu-Medrol
If a severe infection or heart impairment (cardiac tamponade) exists, the extra fluid must be drained immediately:
Pericardiectomy or pericardial window
Pericardial effusions that are 3 months old or older are called chronic. Often, no cause is known. They’re monitored without treatment. If there are symptoms or your heart is being harmed, drainage is usually done.