Pericardial effusion pathophysiology
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Pericardial effusion usually results from a disturbed equilibrium between the production and reabsorption of pericardial fluid. This can occur in infections and inflammations where there is increased production of pericardial fluid or in malignancy and hypothyroidism where there is inadequate drainage of the fluid.
Pericardium surrounds the heart and it consists of two layers, parietal and visceral layers. The space between the layers is known as the pericardial cavity. It usually contains small amount of fluid, approximately 15-50ml, which acts as a lubricating agent between the layers. This fluid enters the pericardial space from the capillaries into the visceral pericardium. This fluid is drained by lymphatics. When this fluid production-drainage mechanism is altered, excess fluid accumulates in the pericardial cavity and this is referred to as pericardial effusion.
Therefore, pericardial effusion occurs when there is:
Increased Production of Pericardial Fluid
1.Increased Capillary Membrane Permeability
Infection or inflammation may lead to exudative fluid or hemorrhagic effusion which have high protein levels. The pericardial effusion observed in the following conditions results from increased permeability of the capillary membrane.
- Viral/bacterial infections such as adenovirus infection and tuberculosis
- Autoimmune diseases such as sarcoidosis, SLE and rheumatoid arthritis
- Penetrating trauma which injure the blood vessels and cause hemorrhage into the pericardial space
- Malignancies such as pulmonary carcinoma may metastasize to the pericardium and can disrupt pericardial anatomy and vasculature