A review of implantable cardioverter defibrillator failures during radiation therapy in three Sydney hospitals

INTRODUCTION: In recent years, using radiation energies greater than 10 MV in patients with implantable cardioverter defibrillators (ICDs) has been contra-indicated due to the risk of a power on reset (POR) occurring. The ICD is often greater than 30 cm from the treatment field and subject to scatter radiation only. The aim of this study was to use recent patient cases to verify published failure rates and treatment recommendations. METHOD: Five patients with ICDs who experienced a device malfunction during radiation therapy treatments were identified in three Sydney hospitals between 2008 and 2012. The types of treatments delivered during these events were assessed. Further assessment of all ICD patients at one Sydney hospital during this time was carried out to assess the rate of ICD failure during high energy treatments using 18 MV. RESULTS: All ICDs that suffered malfunctions were exposed to scatter radiation only. All were exposed to partial or exclusive irradiation using 18 MV photons. Accumulated doses to the ICDs were estimated to be well below accepted dose limits found in literature. One centre reported a 22.2% rate of POR during exposure to 18 MV radiation therapy during this time frame. CONCLUSIONS: Where possible, radiation therapy using energies greater than 10 MV should be avoided for ICD patients. While the use of these energies carries a risk of failure, it must be weighed against potential benefit to the patient requiring treatment if no alternatives are available. Stringent monitoring of these patients, including regular cardiac device checks and ECG monitoring is recommended if treatment is to proceed with energies greater than 10 MV.