Severe pericardial effusion. When pericardial effusion develops, the heart is compressed, diastolic heart filling is impeded, and the patient’s cardiac output, as well as the volume of returned blood, decreases particularly dramatically. Although pericardial effusion is a limited disease in which the heart is the main organ involved, if the disease continues to progress, other organs may also be involved, such as the liver, kidneys, brain, gastrointestinal tract, and blood vessels of the lower extremities. If pericardial effusion is not treated promptly and effectively, it is likely to cause particularly serious complications, such as compression of the esophagus or trachea, cardiogenic shock, and sudden death, which are extremely life-threatening. The presence of pericardial effusion is usually associated with a variety of pathologies, such as blood disorders, autoimmune diseases, tumors, kidney failure, heart failure, and chest infections. Since the causes are complex and varied, it is important to have a proper examination to clarify the cause before proceeding with the relevant treatment.