Epicardium

What is the epicardium?

Your epicardium is the outermost layer of your heart and the inner layer of your pericardium. It surrounds and protects your heart. Together with your myocardium (the muscular middle layer) and endocardium (the inner layer), your epicardium forms your heart wall. Another name for the epicardium is the “visceral layer of the serous pericardium” or simply the “visceral pericardium.”

Epicardium is pronounced eh-puh-CAR-dee-um. Here’s what each part of the word means:

• “Epi” means upon, over or outer.
• “Cardium” means your heart.

What is the function of the epicardium?

Your epicardium is a vital layer of your pericardium. It protects your heart and helps it work normally. There’s a small amount of space between your epicardium and the next layer of your pericardium, called the parietal layer. This space holds a substance (pericardial fluid) that lubricates your heart as it beats within your chest. 

Between your epicardium and your heart muscle, there’s a special kind of fat called epicardial fat or epicardial adipose tissue. This fat sits on top of your coronary arteries and veins, as well as some nerves and lymphatic vessels.

It’s normal to have a small amount of epicardial fat, however, having too much of it may put you at risk for heart disease. Experts believe this is because the fat starts making substances that promote inflammation and plaque buildup. It basically starts doing the opposite of what it’s supposed to do. Future research may help us learn more about this fat and the role it plays in heart disease.

What is the epicardium composed of?

Your epicardium is made up of two layers:

• A single layer of mesothelial cells (special cells that line organs in your body)
• A thin layer beneath those cells that contains collagen and elastin (types of proteins)

Epicardial fat lies just below your epicardium, directly against your heart muscle.

What are the common conditions that affect the epicardium?

Anything that affects your pericardium can affect the epicardium, which is the innermost layer. Examples include:

• Pericarditis: This is inflammation of your pericardium, which usually develops suddenly.
• Pericardial effusion: This refers to excess fluid in the pericardial cavity, which your epicardium helps contain.
• Cardiac tamponade: This is fluid buildup that puts pressure on your heart and keeps it from beating properly.
• Heart attack: The scar tissue that forms after a heart attack often extends from the innermost layer of the heart (endocardium) to the outermost layer (epicardium).

When to seek medical care

Problems with your epicardium (and entire pericardium) can cause a range of symptoms. It’s not always easy to tell the cause. But you should always call your healthcare provider if you have:

• Extreme tiredness you can’t explain
• Heart palpitations
• Racing heart, dizziness and chest pain (symptoms of ventricular arrhythmias)
• Shortness of breath
• Swelling in your legs, feet or belly

Call 911 or your local emergency services number if you have:

• Sharp pain in your chest (it may spread to nearby areas or get worse when you breathe deeply, lie flat or cough)
• Trouble breathing
• Fast breathing
• Fast pulse
• Dizziness or fainting
• Skin that looks gray, blue or paler than usual
• Confusion or changes to your thinking