Pericardial effusion – Fluid collection around the heart
Pericardium is the thin covering of the heart. It has two layers with a thin layer of fluid in between in a normal individual. In certain diseases, fluid collects in between the two layers of the heart and then it is known as pericardial effusion. If the fluid collects gradually, the pericardium stretches to accommodate it so that the function of the heart is not compromised till a large volume of fluid has collected in the pericardial cavity. But if the fluid collection is rapid as in bleeding into the pericardial cavity, the pericardium gets little time to stretch and accommodate the fluid so that the pressures within the pericardial space goes up, compromising the function of the heart. Pericardial fluid at high pressures compresses the right sided chambers of the heart which have lower pressures inside physiologically. First chamber to collapse when the pericardial pressure rises due to fluid collection is the thin walled right upper chamber of the heart known as right atrium. If the pericardial pressure go still higher, right ventricle, the lower muscular chamber of the heart can also get compressed. When the right atrium collapses, filling of the heart by blood returning from the various parts of the body is hampered. This in turn prevents heart from pumping an adequate quantity of blood into the various organs of the body. This situation is known as cardiac tamponade. It is a medical emergency and unless the fluid is removed quickly and the heart is relieved of the compression, it can be catastrophic. The blood pressure drops and the person can become breathless and collapse.
Some amount of pericardial fluid collection can occur in any situation where there is generalised fluid retention in the body as in heart and kidney failure. Pericardial fluid in such situations are thin and watery known as serous fluid with low protein content. When it is due to infections like tuberculosis, the fluid is straw colored with high protein content (Straw colored pericardial fluid). When it is due to a cancerous process or due to injury causing bleeding into the pericardial cavity, pericardial fluid can be blood stained or even frank blood.