The heart is a muscle surrounded by a fibrous sac containing sheath called the pericardium. There is normally 2 to 3 ccs of fluid between the heart and the pericardial lining. If excessive fluid builds up in the space between the pericardium and the heart, this is called a pericardial effusion. A very high build up of fluid can cause cardiac tamponade, in which the heart is compressed by the surrounding fluid and is unable to pump properly.
According to MayoClinic.com, infections with bacteria, viruses or fungi can cause pericardial effusions, or fluid around the heart. Any person is susceptible to an infection leading to this condition, but cancer patients are at an increased risk because they often have a weakened immune system. Chemotherapy, radiation and the effects of the cancer itself, such as infiltration of bone marrow can destroy the cells of the immune system responsible for fighting off infections. As a result, an infectious organism is more likely to breach the body's defenses, infect the pericardium, cause inflammation and the build up of fluid.
Primary cancers are those that are found at their site of origin. Primary cancers that cause pericardial effusions are cancers of the heart and its lining. According to the Merck Manuals, these are very rare, and most tumors in the heart are benign. A tumor causing a pericarial effusion is even more rare, as it would be located near or in the space between the heart and its lining. A heart tumor may arise from connective tissue, muscle, blood vessels or fat.
Metastasis occurs when cancer that originated in one location of the body migrates to another location, usually via the blood stream or lymphatic channels. Metastatic cancers more likely to cause pericardial effusions including breast cancer, lung cancer, leukemia, Hodgkin's lymphoma and non-Hodgkin's lymphoma.
Cancer Treatment and Other Drugs
Radiation is used to treat certain cancers, particularly when they are in a location where it is difficult to operate or when radiation is expected to shrink the tumor to make surgical treatment easier. Radiation to the chest can cause changes in tissues and inflammation. If this happens around the heart, it can lead to fluid build up. Chemotherapy is used to treat primary or metastatic cancers anywhere in the body. These medications are known to cause pericardial effusions, particularly cyclophosphamide and doxorubicin. Other medications, according to MayoClinic.com, include a drug for high blood pressure called hydralazine, a drug for seizures called phenytoin and a drug for tuberculosis called isoniazid.