Effects of High-dose Radiotherapy on Implantable Cardioverter Defibrillators: an in Vivo Porcine Study

Introduction: Although the effects of radiotherapy (RT) on implantable cardioverter defibrillators (ICDs) have been studied in vitro, and some information has been gathered from case reports and series, no in vivo experiments have previously been performed.

Methods: In vivo effects of photon RT applied directly to five modern ICD generators from different manufacturers implanted in pigs were studied. The devices were interrogated between and after increasing doses of ionizing radiation. Afterwards, the shock function was tested.

Results: All ICDs withstood fractionated irradiations with a cumulative dose of 18.5 gray (Gy) of 6 megavolt (MV) photons and 18.5 Gy of 18 MV photons and were still fully functional. Especially, no oversense was recorded. Induced ventricular fibrillation was detected and treated properly by shock therapy in all cases. However, one of the ICDs converted to back-up mode later the same night.

Conclusion: The animal model is feasible for investigating RT effects on implanted cardiac devices. During irradiations with 37 Gy, one recoverable malfunction was present in the tested devices. Additional animal studies could provide supplementary evidence for treating ICD patients, including recommendations for reprogramming of the ICD during RT and avoidance of relocating the device.