Pericarditis is a condition in which the fibrous sac-like covering around the heart becomes inflamed.  Pericarditis typically causes chest pain that worsens when taking a deep breath in, sometimes worsening when lying down and often relieved by sitting up and leaning forward.  The chest pain is caused by the inflamed pericardium rubbing against the heart.  The pain is usually sharp and may radiate to the shoulder, neck, or back. Pericarditis can be caused by an infection, most commonly viral, although bacterial or fungal infections can also be the cause. It can occur due to general inflammation after larger heart attacks or after open-heart or chest surgery. In up to half of cases there is no discernable cause, but pericarditis can be related to auto-immune inflammatory conditions like systemic lupus erythematosus and rheumatoid arthritis, or be caused by certain medications.  Trauma, tumors, cancer, and radiation to the chest are other rare causes.  Pericarditis can cause shortness of breath and be accompanied by fever and fatigue.  Infrequently, arrhythmias like atrial fibrillation can occur. While antibiotics are sometimes required for non-viral infectious causes, most cases are treated with NSAID’s and sometimes cochicine to help decrease the pain and inflammation.  In more severe cases, steroids sometimes are added.  Most patients recover in two to four weeks. The pericardium normally has two layers, an inner pericardium lining the heart and an outer pericardium. There is a very small amount of fluid between the pericardial layers to help prevent friction between the two surfaces and help cushion the heart. When the pericardium is inflamed, it can leak inflammatory fluid which can build up between the layers.  Most cases of pericarditis cause minimal fluid build-up and will gradually resolve. However, pericardial effusions can grow large and if this occurs, the pressure from the fluid build-up can cause the heart to not be able to fill or beat properly.  This can lead to a very serious condition known as pericardial tamponade.  Pericardial tamponade and moderate to large pericardial effusions may require the pericardial effusion to be drained.  This is done with a pericardiocentesis where a needle is inserted through the lower chest and through the pericardium so that fluid can be drained to relieve pressure around the heart.  Sometimes analysis of the fluid removed can help determine the cause. Usually, pericarditis occurs suddenly but it can be more indolent and persistent.   If the pericarditis is not adequately treated, the inflamed pericardium does not heal properly and becomes stiff and can stick to the heart.  This prevents the heart muscle from fully expanding in between heart beats and constricts the function of the.  This is known as constrictive pericarditis but is more appropriately referred to as pericardial constriction.  This can lead to persistent fatigue and shortness of breath, swelling of the feet, legs, and abdomen often with weight gain. Surgical removal of the thickened and stiff pericardium can allow the heart to function properly. Pericarditis is diagnosed based on the patient’s history and cardiologist exam where a “rub” can be heard using a stethoscope from the inflamed pericardial layers rubbing against each other and the heart.  Tests used to help confirm the diagnosis include an EKG; chest x-ray and echocardiogram.  In more severe or chronic cases, cardiac catheterization, cardiac CT scans, or cardiac MRI can be used.