Malfunction of cardiac devices after radiotherapy without direct exposure to ionizing radiation: mechanisms and experimental data.
OBJECTIVE
Malfunctions of cardiac implantable electronical devices (CIED) have been described after high-energy radiation therapy even in the absence of direct exposure to ionizing radiation, due to diffusion of neutrons (n) causing soft errors in inner circuits. The purpose of the study was to analyse the effect of scattered radiation on different types and models of CIED and the possible sources of malfunctions.


RESULTS
Fifty-nine explanted CIED were placed on an anthropomorphous phantom of tissue-equivalent material, and a high-energy photon (15 MV) radiotherapy course (total dose = 70 Gy) for prostate treatment was performed. All devices were interrogated before and after radiation. Radiation dose, the electromagnetic field, and neutron fluence at the CIED site were measured. Thirty-four pacemakers (PM) and 25 implantable cardioverter-defibrillators (ICD) were analysed. No malfunctions were detected before radiation. After radiation a software malfunction was evident in 13 (52%) ICD and 6 (18%) PM; no significant electromagnetic field or photon radiations were detected in the thoracic region. Neutron capture was demonstrated by the presence of the (198)Au((197)Au + n) or (192)Ir((191)Ir + n) isotope activation; it was significantly greater in ICD than in PM and non-significantly greater in damaged devices. A greater effect in St Jude PM (2/2 damaged), Boston (9/11), and St Jude ICD (3/6) and in older ICD models was observed; the year of production was not relevant in PM.


CONCLUSIONS
High-energy radiation can cause different malfunctions on CIED, particularly ICD, even without direct exposure to ionizing radiation due to scattered radiation of neutrons produced by the linear accelerator.
Cardiovascular Department, University and Hospital, Trieste, Italy massimo.zecchin@alice.it massimo.zecchin@aots.sanita.fvg.it.
Massimo
M
Zecchin
Cardiovascular Department, University and Hospital, Trieste, Italy.
Gaetano
G
Morea
Department of Medical Physics, University and Hospital, Trieste, Italy.
Mara
M
Severgnini
Department of Physics, University, Trieste, Italy.
Elisabetta
E
Sergi
Department of Physics, University, Trieste, Italy.
Anna
A
Baratto Roldan
Cardiovascular Department, University and Hospital, Trieste, Italy.
Elisabetta
E
Bianco
Cardiovascular Department, University and Hospital, Trieste, Italy.
Silvia
S
Magnani
Cardiovascular Department, University and Hospital, Trieste, Italy.
Antonio
A
De Luca
Cardiovascular Department, University and Hospital, Trieste, Italy.
Anna
A
Zorzin Fantasia
Cardiovascular Department, University and Hospital, Trieste, Italy.
Luca
L
Salvatore
Radiotherapy Department, University and Hospital, Trieste, Italy.
Vittorino
V
Milan
Department of Physics, University, Trieste, Italy.
Gianrossano
G
Giannini
Cardiovascular Department, University and Hospital, Trieste, Italy.
Gianfranco
G
Sinagra
D017147:Defibrillators, Implantable; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D009502:Neutrons; D010138:Pacemaker, Artificial; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D012542:Scattering, Radiation; D012985:Software Design
CIED malfunction; Implantable cardioverter-defibrillator; Pacemaker; Radiotherapy; Scattered radiation; Soft errors