Test Details: The pericardium is a two-layered, sac-like membrane that surrounds the heart. Pericardial membrane produces pericardial fluid which acts as a lubricant for the movement of the heart, reducing friction as the heart pumps blood. A variety of conditions and diseases can cause inflammation of the pericardium (pericarditis) and/or excessive accumulation of pericardial fluid (pericardial effusion). This test is used to help diagnose the various causes of pericarditis and/or pericardial effusion.