[Adequate performance of a pectoral implanted defibrillator after high-dose radiation therapy for thyroid cancer].

The interference of implanted defibrillators (ICD) from electronic appliances is small. There is scant knowledge about the effects of radiation therapy on defibrillator function. Existing data commonly derive from in vitro tests of the devices. We report on a 60-year old male patient with a left pectoral implanted ICD, who received radiation therapy for treatment of thyroid cancer.    The patient suffered from coronary heart disease with severely impaired left ventricular function, and had to be resuscitated from ventricular fibrillation in December 1997. A defibrillator (Medtronic Jewel 7219 C) was implanted in a left pectoral pocket. In January 2000, a carcinoma of the thyroid gland was diagnosed and treated surgically. The operation was followed by a radiation therapy with curative intention. The patient received a local dosage of 64 Gray (32 sessions in 51 days). The ICD was covered by individually sized metal blocks, and was affected by 10 Gray at maximum. The ICD was inactivated during the radiation applications to avoid inadequate therapy due to electromagnetic interference. The pace-sense parameters during 8 months of follow-up were regular. Three episodes of ventricular fibrillation were terminated adequately by the ICD. Therefore, we assumed a correct ICD funtion after radiation therapy.    Radiation-induced damage of the ICD was possible. A surgical transfer of the generator out of the radiation area was rejected on ethical grounds. In the short follow-up period, the ICD function was correct. For our opinion it seems to be justified primarily to control the spontaneous outcome and ICD function at short intervals, especially in view of the poor prognosis of cancer patients.