The heart is surrounded by a sac known as the pericardium, which is made up of two layers – the fibrous and serous pericardium. The inner lying serous pericardium is in turn composed of two linings – the parietal and visceral layers of the serous pericardium. The visceral layer of the serous pericardium is attached to the heart and makes up the outer layer of the heart wall known as the epicardium. The parietal layer of the serous epicardium is fused with the fibrous pericardium. A potential space therefore exists between the visceral and parietal layers of the pericardium in between known as the pericardial space. Within this space is a small amount of fluid known as the pericardial fluid that serves as a lubricant for the constantly beating heart. However, excess fluid can accumulate within this cavity and cause a host of signs and symptoms.
What is a pericardial effusion?
A pericardial effusion is the accumulation of fluid in the pericardial space between the parietal and visceral layers of the pericardium. It is commonly referred to as fluid around the heart since the visceral layer is continuous with the epicardium – the outermost layer of the heart wall. Although the pericardial space can accommodate small volumes of fluid, even beyond the 15 to 50 milliliters of pericardial fluid it normally contains, an excess will ultimately restrict the heart movement and compress the heart. A pericardial effusion is therefore an abnormal and excess amount of fluid around the heart within the pericardial space.
Types of Fluid Around The Heart
An effusion is often associated with pericarditis – inflammation of the pericardium. The nature of the disease that causes pericarditis contributes to the type of fluid that will accumulate in the pericardial space. This is discussed further along with possible causes under types of pericarditis.
A serous effusion is associated with irritation of the pericardium with an excess of fluid secreted by the visceral layer of the serous pericardium. The inflammatory infiltrate contains a few lymphocytes and does not differ significantly from normal pericardial fluid. A fibrinous effusion contains fibrin (fibrinous exudate) which can become organized and form adhesions. Hemorrhagic effusion is when blood is mixed with the exudate while a purulent effusion is the collection of pus around the heart and seen in infectious causes.
Causes of Fluid Around the Heart
This is a leading cause of acute cases and is usually due to an infection of the pericardium (infectious pericarditis). It can also arise with inflammation of the myocardium (myocarditis) – the muscular layer of the heart. It is more commonly seen with viral and bacterial infections but less frequently, it may be due to fungal, protozoal or parasitic infections. Systemic infections and dissemination from neighboring or distant sites may also contribute to an infection, as is seen with HIV/AIDS, tuberculosis (TB) and syphilis.
A significant number of cases are due to unknown causes of pericardial inflammation (idiopathic pericarditis). Underlying diseases, particularly autoimmune diseases, should be investigated.
This occurs when the body’s immune system attacks the pericardium and the resulting inflammation contributes to the development of an effusion. It may occur in the backdrop of known autoimmune conditions like rheumatoid arthritis, systemic lupus erythematosus (SLE) and scleroderma.
Malignancy of the heart or pericardium more frequently arises as a result of metastases – spread from a neighboring or distant site. This may occur with direct extension, lymphatic or hematogenous (via the bloodstream) spread. A pericardial effusion associated with malignancy is more commonly seen with cancer of the breast, lung, lymphoma (lymphatic), leukemia (blood) or melanoma (skin). Radiation therapy to treat thoracic tumors and chemotherapy in the treatment of cancer may also cause an accumulation of fluid around the heart.
- Hypothyroidism (myxedema)
- Aortic dissection (rupture of the aorta)
- Post-operative (Dressler’s syndrome)
- Various drugs include medication for hypertension, epilepsy, and tuberculosis
Signs and Symptoms of Pericardial Effusion
The pericardium has the ability to accommodate a significant amount of fluid and symptoms will only be noticed once it approaches this maximum capacity thereby compressing the heart (cardiac tamponade) significantly. The clinical presentation closely resembles the symptoms of pericarditis and includes :
- Shortness of breath (dyspnea) especially when lying down (orthopnea)
- Dry cough
- Retrosternal pressure and eventually pain (breastbone pain) which worsens with breathing and coughing
- Tachycardia (rapid heart rate) with low blood pressure (hypotension)
- Low-grade fever particularly with infectious causes
- Dizziness or fainting
- Diminished heart sounds
- Pericardial friction rub