Recurrent syncope 20 years after mediastinal radiation therapy in a patient with breast cancer.

Mediastinal radiation therapy can cause progressive fibrosis and might, as a result, induce various cardiac problems. We encountered a patient who presented with recurrent syncope 20 years after radiation therapy for breast cancer. She had multiple cardiac problems including bilateral coronary ostial stenoses, pre-valvular right ventricular outflow tract stenosis, and constrictive pericarditis. The cause of syncope was paroxysmal atrioventricular block (an 18-s long pause recorded by the implantable loop recorder). The patient was treated by the implantation of a pacemaker and did not experience syncope during 9 months of follow up.