P2858Cardiac implantable device malfunctions during radiotherapy courses up to 10 Gy: a double-center, prospective, randomized, in-vitro evaluation

Abstract

Abstract Background Exposure to radiotherapy in patients with cardiac implantable electronic devices (CIEDs), both pacemakers (PMs) or implantable cardioverter defibrillators (ICDs), seems to be still troubleshooting. Unlike magnetic resonance imaging, high dose photon radiation at even less than 6MV power, notoriously a non-neutron-producing setting, may transiently or permanently affect normal device function. Malfunctions may be harmfull and life-threatening in high risk patients, such as PM-dependent or ICD ones. Purpose To evaluate CIED malfunctions by direct exposure to doses more than 2Gy in oncologic radiotherapy, 162 CIEDs (116 PMs and 46 ICDs) from two different centers, with at least 4 months to Elective Replacement Indicator (E.R.I.) were evaluated. Methods All CIEDs had a baseline telemetry interrogation. Single chamber devices were programmed in the VVI/40 mode and dual or triple chamber devices were programmed in the DDD/40 mode. Rate adaptive function was disabled. In ICDs, antitachycardia therapies were disabled with the ventricular tachycardia/fibrillation monitor still enabled. To build the corresponding treatment plan a centering Computed Tomography was performed and CIEDs were blinded randomized (4:4:4) to either 2, 5 or 10 Gy direct exposure by a low photon-energy LINAC (6MV) in a water phantom. An in-vivo dosimetry assessed the effective dose received by the CIEDs. All CIEDs had a telemetry-interrogation, using manufacturer specific equipment, immediately after exposure and monthly for a four-month follow-up. Results Immediately after exposure, 1 reset to emergency mode was observed in a PM (0.6% overall; 0.9% among PMs)), while 7 PMs reached the E.R.I immediately after exposure (4.3% overall; 6% among PMs). 10 ICDs (6.2% overall; 21.8% among ICDs) reporded multiple ventricular fibrillation detection stored in the device memory. During follow-up, 3 PMs (1.9% overall; 2.6% among PMs) and 1 ICD (0.6% overall; 2.2% among ICDs) reached the E.R.I. and 1 PM (0.6% overall; 0.9% among PMs) switched to emergency mode. All reported events occurred regardless of either 2, 5, or 10 Gy direct exposure. Malfunctions were observed in only older CIEDs. Conclusions Our data suggest recent CIEDs withstanding direct oncologic radiotherapy exposure up to 10 Gy, commonly considered not recommended or even unsafe by manufacturer statements and clinical guidelines. Malfunctions occurred in only older devices. Acknowledgement/Funding None