Fluid buildup in the heart, known as pericardial effusion, is generally not life-saving when treated aggressively; the cause needs to be sought and treated to relieve the pressure of the effusion on the heart. In general, pericardial effusion has no effect on life expectancy, but the primary disease causing the effusion may affect a person’s survival. Common causes can be categorized into infectious and non-infectious factors. Infectious factors include tuberculous pericarditis, viral myocarditis, etc.; non-infectious factors include heart rupture, acute infarction, and neoplastic diseases. The above diseases may be life-threatening if they produce a large amount of pericardial effusion in a short period of time leading to pericardial tamponade, but they do not affect survival when they are produced slowly and in small amounts. In the case of pericardial effusion, it is necessary to actively search for the primary disease and treat it. If the amount of effusion is large enough to cause discomfort, it can be reduced by pericardiocentesis.