Pericardial effusion pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Varun Kumar, M.B.B.S.
Overview
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.
Pathophysiology
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
- Decreased drainage of pericardial fluid
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
2.Increased Microvascular Pressure
Hypervolemic states like cardiac failure and renal failurecause pericardial effusion due to increased microvascular pressure.
3.Decreased Plasma Oncotic Pressure
Pericardial effusion seen in cirrhosis and nephrotic syndrome is due to decreased plasma oncotic pressure secondary to hypoalbuminemia.
Decreased Drainage of Pericardial Fluid
Pericardial effusion may occur in malignancies and hypothyroidism due to decreased drainage of the pericardial fluid by the lymphatics.