The pericardium is a thin fibrous membrane sac that surrounds the heart. The pericardium consists of an inner layer (visceral pericardium) that envelopes the entire heart, and an outer layer (parietal pericardium) comprising the outer fibrous sac and a middle fluid layer to prevent friction between the parietal pericardium and visceral pericardium.
When too much fluid builds up between the layers of the heart this is called a pericardial effusion. It can occur after open heart surgery, secondary to heart failure, tumors, lupus, bacterial or viral infection, or radiation treatment. You may require a thoracentisis (a needle inserted) or a more permanent procedure called a pericardial window to relieve the pressure of the fluid on the heart muscle. The procedure is performed through a small incision under the breastbone under a general anesthetic. A two to three day hospital stay generally follows.
In some cases inflammation of the pericardial sac results in fibrosis and thickening of the pericardium with adhesions (i.e., sticky scars) between the pericardium and the heart. The pericardium creates a rigid "case" around the heart and can severely limit the ability of the heart to fill with blood during diastole (i.e., the relaxation phase before the next heartbeat). Patients with constrictive pericarditis may develop heart failure which responds poorly to treatment. In these cases a pericardiectomy, or surgical removal of the pericardium is indicated.