Constrictive pericarditis is stiffening and thickening of the membrane sac around the heart (pericardium). Repeated or prolonged episodes of inflammation of the pericardium (pericarditis) can lead to constrictive pericarditis, which restricts the heart's ability to pump effectively.

Constrictive pericarditis can be caused by medical conditions or treatments that involve inflammation. These include radiation therapy and complications after surgery. But the cause is often unknown.

If the pericardium becomes thick and stiff and interferes with the heart's ability to pump blood, it can be removed in a procedure called pericardiectomy. Although the pericardium surrounds and cushions the heart, the heart can function without it, if necessary.