Does radiotherapy effect the voltage output of cardiac implantable electronic devices (CIEDs)?

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. PURPOSE: Current guidelines for the management of patients undergoing radiotherapy with cardiac implantable electronic devices (CIEDs) were published in 1994. They recommend that the total dose received by the device should be estimated before treatment, devices should not be placed in the direct radiation beam and the cumulative dose should not exceed 2Gy to any part of a pacemaker (0.5Gy for ICDs). This is because radiotherapy can cause malfunctions in cardiac implantable devices. At doses higher than this, relocation of the device is recommended. Device malfunctions are suggested to correlate with a beam energy of ≥10MV. One malfunction that poses a high risk to patients is a change in voltage output amplitude. This study assessed if low-energy flattening filter and high energy flattening filter-free photon beam radiation caused a change in the voltage output amplitude of cardiac implantable devices. METHOD: 40 cardiac implantable devices were divided into two treatment groups and irradiated in vitro with a cumulative 48Gy dose of 6MV radiation at 600MU/min in 8 fractions or a 48Gy dose of 10MV radiation at 2400MU/min. The voltage output amplitude of all devices was collected using an oscilloscope and an amplitude change of ≥25% was classed as a clinically significant malfunction. RESULTS: In the 6X treatment group, 0/19 devices showed a clinically significant change. No statistical significant difference was found between the median peak voltage output amplitude before fraction 1 and after fraction 8 (U = 149.5, p = 0.3733, n =19). In the 10MV treatment group, 2/21 devices showed a clinically significant change. These devices showed a voltage output amplitude increase of 28.07% and 36.97%. However, no statistical significant difference was found between the median peak voltage output amplitude before and after radiation (U = 149.5, P = 0.0746, n = 21). Although insignificant, there was clearly a larger change across all devices in the 10FFF group compared to the 6X group. Results were not statistically significant between manufacturers but defibrillators were statistically significantly more likely to malfunction than pacemakers. CONCLUSION: The recommended dose of radiotherapy for patients with a CIED should be carefully considered on an individual basis. Due to neutron production and its effect on rapid access memory (RAM) and complementary metal oxide semiconductor (CMOS) circuitry, high-energy ≥10MV radiation can affect the voltage output amplitude, despite its statistical insignificance. Based on this limited report it is unlikely that the voltage output amplitude of CIEDs will be affected by clinically relevant doses of radiotherapy, but it may have long term implications on battery life. These results could eliminate the risk of increased infection due to relocation of devices, provide patients with optimised treatment and enable a more effective service for improved patient management.