[Radiation toxicity to the heart: physiopathology and clinical data]

Irradiation of the heart begets different complications in which pericardial disease is the most common manifestation. Thoracic irradiation of lymphoma, Hodgkin's disease, lung and breast cancer could be complicated by adverse effects to every structure of the heart. Potential injury of mediastinal irradiation can include acute and late pericarditis, cardiomyopathy, valvular disease and conduction abnormalities. The pathophysiology of these various syndromes is probably similar, starting by prior microvascular injury that leads to subsequent myocardium ischemia, all of which cause late fibrous scars. Acute pericarditis is often asymptomatic and clear spontaneously. Late pericarditis affects approximately 5% of the patients when the irradiation dose exceeds 40 Gy. At this dose, the mortality rate is below than 1%. Cardiomyopathy is rare and often asymptomatic. A long time unrecognized, coronary artery disease, diagnosed in 5 to 10% of the patients, begets multifarious sequelae like myocardial infarction, valvular abnormalities and cardiac rhythm changes. This coronary artery disease is more likely to occur if the patient was young at the time of the irradiation (< or = 21 years) and/or if other cardiovascular risk factors are associated. Incidence and mortality rates of valvular defects are about 20 and 0.5%, respectively. Conduction dysfunctions can also be seen in 5% of the patients. Radiation-induced heart complications seem to be related to total dose (> 30 Gy), irradiated tissue volume and fraction size. Since cardiac complications appear months to years following incidental irradiation of the heart, appropriate screening and long-term cardiac follow-up of these patients is essential.