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. 2025 Jul 2:35:100804.
doi: 10.1016/j.phro.2025.100804. eCollection 2025 Jul.

In-vitro effects of modern radiotherapy regimes on cardiac implanted electrical devices

Steven Manley  1   2 , Amy Fenwick  3 , Megan Fraser  3 , Mark Lowrey  3 , Anna Walaszczyk  3 , Nick West  2   4
Affiliations

In-vitro effects of modern radiotherapy regimes on cardiac implanted electrical devices

Steven Manley et al. Phys Imaging Radiat Oncol. .

Abstract

Background and purpose: External Beam Radiotherapy (EBRT) of patients with Cardiac Implanted Electrical Devices (CIEDs) have guidelines developed over many decades, during which both technologies have advanced. Consequently, guidelines may not reflect modern device interactions. Asynchronous modes, with pace sensing and shocks turned off whilst regulating pacing output, is used routinely for MRI scanning and could reduce risks for pace sensing errors in radiotherapy. Evidence is limited on modern radiotherapy using high dose, high doserate beams, with CIEDs in asynchronous mode. We present the effects of irradiating modern CIEDs using contemporary radiotherapy regimes.

Materials and methods: One hundred and sixty explanted CIEDs were irradiated, to corroborate historical findings for modern devices in normal operational modes, and explore effects when in asynchronous mode. Regimes knowingly detrimental to CIEDs; 48 Gy single fraction, neutron producing, alongside clinically relevant regimes of 60 Gy in 5 fractions using 10 MV flattening filter free [FFF] beams at clinical, and maximal dose rates.

Results: No significant changes occurred to pacing voltages from 60 Gy in 5 fractions 10 MV FFF deliveries in asynchronous mode.No evidence supported restricting 6 MV flattened beams for CIED patients, including defibrillation capable devices.

Conclusions: This study demonstrates asynchronous mode can reduce the frequency of CIED malfunctions during EBRT. However, clinical context, risks and benefit must be evaluated per patient. While some current guidelines potentially compromise plan quality to reduce dose to the CIED, the use of asynchronous mode may provide planning options, which more closely align to non-CIED cases.

Keywords: CIED; FFF; High dose rate; Pacemaker; Radiotherapy; SABR.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Schematic of EBRT set-up for initial experiments. Top: experiments 1a and 1b leads in saline. Bottom: Experiments 2a, 2b, 3a and 3b output capture via Picoscope.
Fig. 2
Fig. 2
Box plots for the CIED’s exposed to 6 MV photons for 8 fractions (Fx 1, Fx 2, etc.,) of 6 Gy each, from experiment 2a. Median dose indicated by a solid line, mean by a cross. Given the overall stability of the cohort of devices used in this 6 MV experiment, no further fault analyses were performed.
Fig. 3
Fig. 3
Top: 12 Gy/minute (experiment 3a), bottom: 24 Gy/minute (experiment 3b). Median output pulse voltage box-plots for the 10 MV deliveries in experiments 3a and 3b, with standard quartiles at 25 % and 75 %, using an inclusive median calculation. Each device was programmed and then self-reported as being set to output −2.5 V. Median per fraction values denoted by a line, mean values with a cross and outliers indicated by circles beyond the quartiles. Outliers are all from three specific devices; 2 in the 12 Gy/min group and 1 in the 24 Gy/min group. Fraction 1’Pre’ being prior to EBRT.
See this image and copyright information in PMC

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