P682Radiotherapy-induced malfunction in cancer patients with cardiac implantable electronic devices

Abstract Background The number of patients with cardiac implantable electronic devices (CIED) requiring a radiation therapy (RT) for cancer treatment is increasing over time. Nevertheless, the rate and predictors of CIED malfunctions are still controversial. Purpose The aim of our study is to estimate the prevalence and possible predictors of RT-related CIED malfunctions and to describe malfunction characteristics. Methods We retrospectively reviewed medical records of all pacemaker (PM)/implantable cardioverter defibrillator (ICD) patients who underwent RT at our centre between January 2004 and July 2018. We included data from the CIED interrogation performed before the RT course to the first interrogation after the end of the RT course. As a safety measure, during RT a magnet was applied to every ICD and, in all PM-dependent patients, the device was temporarily reprogrammed in V00. Device relocation from the RT field was performed in 2/150 (1.3%) RT courses. Results One hundred twenty-seven patients were included, who underwent 150 separate RT courses. Eighty one percent of patients had a PM, while 19% had an ICD. Of note 17.4% of patients were PM-dependent. Neutron producing RT was used in 37/139 (26.6%) patients, whereas marginal neutron producing and non-neutron producing RT was used in 9/139 (6.4%) and 93/139 (67%) patients respectively. The cumulative dose (Dmax) delivered to the CIED exceeded 5Gy only in 2/132 (1.5%) cases. Three device-related malfunctions were found (2%). None of them were life-threatening or lead to a clinical event. All dysfunctions were resolved by reprogramming the device and did not require CIED substitution or leads extraction. Details of dysfunctions included: 1) a partial reset of an ICD, leading to self-reprogramming in safety mode, 2) full reset of a PM, which required the re-initialisation of the device and 3) programming change of the magnetic PM frequency to 30bpm (instead of 90 bpm). In all cases the Dmax delivered to the CIED was