Purpose:
Ionizing radiation may interfere with cardiac implantable electronic devices (CIEDs), yet clinically relevant malfunctions have become increasingly rare with modern intensity-modulated radiotherapy (IMRT) and low-energy photon beams. This study reevaluates the necessity of intensive daily CIED monitoring by incorporating repeated device assessments and extended follow-up data beyond four weeks after treatment.
Methods:
Between 2014 and 2022, data from 106 patients (146 treatment courses) undergoing radiotherapy were analyzed, comprising 1,830 individual CIED interrogations. Skin dose above the CIED was measured using semiconductor or ion chamber dosimetry and complemented by calculated dose estimates. Device parameters were systematically recorded at multiple timepoints: before treatment, after the first session, mid-course, at treatment completion, and during follow-up visits ≥4 weeks after radiotherapy.
Results:
No significant changes were observed in lead-related pacing threshold, sensing and impedance at any measurement point, regarding right ventricular, right atrial as well as coronary sinus leads, based on a median of 15 obtained interrogation (each p = n.s.). Battery voltage also remained stable, showing no significant variation and no difference regarding VVI, DDD or CRT systems (each p = n.s.). Follow-up data were available for 84 of 106 patients at a median of 69 days after last radiotherapy session. Again, no alterations were detected - all parameters remained stable at the extended follow-up beyond four weeks compared to pre-radiotherapy values (all p = n.s.). Prescribed planning target volume (PTV) doses ranged from 3 to 78 Gy. The median cumulative measured dose above the CIED was 0.76 Gy, and the median calculated dose was 1.00 Gy. No device malfunctions occurred with beam energies >10 MeV. Four minor, clinically irrelevant deviations were noted in IMRT treatments with 6 MV beams, none involving devices within the PTV.
Conclusion:
Longitudinal multi-timepoint and follow-up interrogation data confirm that CIED malfunctions during radiotherapy are exceedingly rare. Extended monitoring after treatment provides no additional safety benefit. These findings support current EHRA recommendations and suggest that routine daily CIED interrogation can safely be omitted in selected low-risk patients without compromising long-term device function.
