In vitro assessment of contemporary leadless and transvenous pacemakers during photon-based radiotherapy

Radiation therapy (RT) is widely used contemporarily, yet concerns persist regarding its potential impact on cardiac implantable electronic devices. Current recommendations are largely based on legacy transvenous pacemakers (tvPMs), and data on leadless pacemakers (LPMs) remain limited.

This study aimed to evaluate the RT tolerance of LPMs and contemporary tvPMs under stereotactic body RT (SBRT) and during supraclinical dose escalation.

Sixteen devices (11 LPMs and 5 tvPMs) were tested in vitro with a thoracic anthropomorphic phantom. Clinically simulated SBRT was delivered using 6-MV photon beams (tumor dose of 54 Gy) at cumulative device doses of 1.15-1.29 Gy for LPMs and 1.81 Gy for tvPMs. A subset of LPMs additionally underwent robotic stereotactic radiosurgery. Subsequently, open-field irradiation with dose escalation was performed up to 200-330 Gy, with 1 LPM exposed to 1055 Gy. Devices were interrogated before and after each irradiation and at late follow-up.

No device resets, pacing mode changes, loss of programmability, or integrity alerts were observed during and after SBRT, robotic stereotactic radiosurgery, or open-field irradiation up to 200-1055 Gy. Battery voltage remained stable in all systems except for 1 LPM exposed to 1055 Gy, in which a late reduction in estimated battery capacity occurred. All telemetry and device interrogations were undisturbed.

In an anthropomorphic phantom model, modern LPMs and tvPMs demonstrated resistance to RT during clinically simulated SBRT and at doses far exceeding those encountered clinically. These findings suggest that radiation sensitivity of contemporary pacemakers may be lower than that observed in legacy devices.