The pericardium is a two-layered membrane that surrounds the heart. The inner layer, or visceral pericardium, adheres to the heart’s surface. The parietal pericardium is the tough outer layer. It anchors the heart in the central part of the thorax (the chest region) and attaches to the breastbone (sternum), the diaphragm, and an area near the lungs. A lubricating fluid separates the two layers, preventing them from rubbing together as the heart beats.

The pericardium secretes body chemicals called prostaglandins that affect the heart’s reflexes and muscle tone. It also may act as a barrier that protects the heart.

Inflamed membrane puts pressure on the heart

The pericardium may become inflamed due to an infection (usually viral, sometimes bacterial), a heart attack or other injury to the heart, or a disease—particularly autoimmune disorders such as rheumatoid arthritis or lupus. With this inflammation, known as pericarditis, abnormally large amounts of fluid are secreted. The fluid builds up and puts pressure on the heart. The heart is then less able to pump blood. The effect on the heart depends on how much, and how quickly, fluid accumulates.

Pericarditis usually causes sharp chest pains that can be severe. Pain is felt behind the breastbone, sometimes reaching the neck, the left shoulder, and the area between the shoulder blades. Inhaling and lying down may make the pain worse; sitting forward, however, may relieve it. Other symptoms include rapid heartbeat, shortness of breath, distended neck veins, a sick feeling, and fever. But pericarditis can also occur without any symptoms, particularly when it’s brought on by rheumatoid arthritis.

Treatment

If it’s caused by underlying disease, pericarditis usually improves when that ailment is treated. If the culprit is a viral infection, pericarditis typically responds to treatment with aspirin or another nonsteroidal anti-inflammatory drug (NSAID).