Pericardial injury from mediastinal irradiation.

The absence of radiation induced cardiac damage during the orthovoltage era, during which period much lower doses of radiation were delivered for mediastinal malignancies due to severe skin reactions, was misinterpreted as cardiac radioresistance. However, with the advent of supervoltage x-rays with skin sparing effect, much higher doses of irradiation have been given for mediastinal malignancies. This has resulted in higher doses of radiation to the heart resulting in various types of radiation induced cardiac damage. The most common site of damage is to the pericardium, resulting in pericardial effusion. The radiographic evidence of radiation induced pericardial effusion starts one to six months prior to signs and symptoms due to it. Most of the asymptomatic radiation induced pericardial effusions resolve spontaneously. The factors which appear to play a role in the development of radiation induced pericardial effusion are discussed.