Pericardial Fluid Analysis

Pericardial fluid analysis is used to help diagnose the cause of inflammation of the pericardium (pericarditis) and/or fluid accumulation around the heart (pericardial effusion). There are two main reasons for fluid accumulation: an imbalance of pressure within blood vessels or inflammation of the pericardium. An initial set of tests, including fluid protein or albumin level, cell count, and appearance, is used to differentiate between the two types of resulting fluids, called transudate and exudate.

• Transudate—an imbalance between the pressure within blood vessels (which drives fluid out of the blood vessel) and the amount of protein in blood (which keeps fluid in the blood vessel) can result in accumulation of fluid. Transudates are most often caused by congestive heart failure or cirrhosis. If the fluid is determined to be a transudate, then usually no more tests on the fluid are necessary.
• Exudate—injury or inflammation of the pericardium may cause abnormal collection of fluid (called an exudate). Exudates are associated with a variety of conditions and diseases. If the fluid is an exudate, then several additional tests may be ordered to help diagnose the specific condition, which may include:
  • Infectious diseases – caused by viruses, bacteria, or fungi. Infections may originate in the pericardium or spread there from other places in the body. For example, pericarditis may follow a respiratory infection or a chest cold.
  • Bleeding – bleeding disorders and/or trauma can lead to blood in the pericardial fluid.
  • Inflammatory conditions – pericarditis may follow a heart attack, radiation treatment, or be part of autoimmune disorders such as rheumatoid arthritis and lupus.
  • Cancer – such as mesothelioma that has arisen in the pericardium or metastatic cancer that has spread to it.

Additional testing on exudate fluid may include:

• Pericardial fluid glucose
• Microscopic examination—a laboratory professional may place a sample of the fluid on a slide and examine it under a microscope. Normal pericardial fluid has small numbers of white blood cells (WBCs) but no red blood cells (RBCs) or microorganisms. Laboratories may examine drops of the pericardial fluid and/or use a special centrifuge (cytocentrifuge) to concentrate the fluid’s cells at the bottom of a test tube. Samples are placed on a slide, treated with a special stain, and an evaluation of the different kinds of cells present is performed.
• Cytology—a laboratory professional may use a cytocentrifuge to concentrate the fluid’s cells on a slide. The slide is treated with a special stain and evaluated for abnormal cells, such as malignant cells (cancer cells).
• Gram stain—for direct observation of bacteria or fungi under a microscope. There should be no organisms present in pericardial fluid.
• Bacterial culture and susceptibility testing—ordered to detect any microorganisms, which will grow in the culture, and to guide antimicrobial therapy.
• Adenosine deaminase—rarely, this test may be used to help detect tuberculosis (TB).
• Less commonly ordered tests for infectious diseases, such as tests for viruses, mycobacteria (AFB smear and culture), and parasites.

Pericardial fluid analysis may be ordered when a healthcare practitioner suspects that a person has a condition or disease that is causing pericarditis and/or pericardial effusion. It may be ordered when someone has some combination of the following signs and symptoms:

• Chest pain, sharp or sometimes dull, that may be relieved by bending forward
• Coughing
• Difficulty breathing
• Fever
• Fatigue
• Changes in heart rhythm
• Enlarged heart size on chest X-ray
• Abnormal pericardial appearance on echocardiogram

Test results can help distinguish between types of pericardial fluid and help diagnose the cause of fluid accumulation. The initial set of tests performed on a sample of pericardial fluid helps determine whether the fluid is a transudate or exudate.

Transudate

Transudates are most often caused by either congestive heart failure or cirrhosis. Typical fluid analysis results include:

• Physical characteristics—fluid appears clear
• Protein or albumin level—low
• Cell count—few cells are present

Exudate

Exudates can be caused by a variety of conditions and diseases. Initial test results may show:

• Physical characteristics—fluid may appear cloudy
• Protein or albumin level—high
• Cell count—increased

Additional test results and their associated causes may include:

Physical characteristics – the normal appearance of a sample of pericardial fluid is straw-colored and clear. Abnormal results may give clues to the conditions or diseases present and may include:

• Milky appearance—may point to lymphatic system involvement.
• Reddish pericardial fluid may indicate the presence of blood.
• Cloudy, thick pericardial fluid may indicate the presence of microorganisms and/or white blood cells.

Chemical tests – in addition to protein or albumin, a glucose test may be performed. Glucose in pericardial fluid samples is typically about the same as blood glucose levels. It may be lower with infection.

Microscopic examination – normal pericardial fluid has small numbers of white blood cells (WBCs) but no red blood cells (RBCs) or microorganisms. Results of an evaluation of the different kinds of cells present may include:

• Total cell counts—quantity of WBCs and RBCs in the sample. Increased WBCs may be seen with infections and other causes of pericarditis.
• WBC differential—determination of percentages of different types of WBCs. An increased number of neutrophils may be seen with bacterial infections.
• Cytology—a cytocentrifuged sample is treated with a special stain and examined under a microscope for abnormal cells. This may be done when a mesothelioma or metastatic cancer is suspected. The presence of certain abnormal cells, such as tumor cells or immature blood cells, can indicate what type of cancer is involved.

Infectious disease tests – routine tests may be performed to look for microorganisms if infection is suspected:

• Gram stain—for direct observation of bacteria or fungi under a microscope. There should be no organisms present in pericardial fluid.
• Bacterial culture and susceptibility testing—if bacteria are present, susceptibility testing can be performed to guide antimicrobial therapy. If there are no microorganisms present, it does not rule out an infection. Bacteria may be present in small numbers or their growth may be inhibited because of prior antibiotic therapy.
• Adenosine deaminase—a markedly elevated level in percardial fluid in a person with symptoms that suggest tuberculosis means it is likely that person has a Mycobacterium tuberculosis infection in the pericardium. This is especially true when there is a high prevalence of tuberculosis in the geographic region where a person lives.

Other less common tests for infectious diseases may be performed. Those tests may identify pericardial fluid accumulation due to a viral infection, mycobacteria (such as the mycobacterium that causes tuberculosis), or a parasite.

Increased amounts of pericardial fluid can restrict the movement of the heart. Cardiac tamponade is a condition that reflects pericardial fluid buildup to the point that pressure on the heart prevents it from filling normally. Rapid fluid buildup can be a medical emergency, causing heart failure and death. When fluid accumulates slowly, the pericardial sac stretches and symptoms gradually worsen.

A blood glucose, protein, or albumin test may be ordered to compare concentrations with those in the pericardial fluid.

Pericardiocentesis is the removal of pericardial fluid from the pericardial sac with a needle and syringe. An intravenous (IV) line may be started and the person may be given medications prior to the sample collection. The individual being tested lies down and a healthcare practitioner applies local anesthetic to the chest. The practitioner then inserts a needle into the space between the ribs (fifth to sixth intercostal space) on the left side of the chest and into the pericardial sac and removes a fluid sample. An ultrasound may be used to help guide the needle.

Yes. Sometimes it will be performed to drain excess pericardial fluid – to relieve pressure on the heart and/or to aid in the treatment of an infection. Sometimes a catheter drain is left in place for a period of time to remove larger amounts of fluid and to drain recurrent fluid accumulations. Sometimes medications will be introduced into the space during the pericardiocentesis.