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Background: There is an increasing number of patients with cardiac implantable electronic devices (CIED), either pacemakers or defibrillators, who are receiving a course of radiotherapy. Several guidelines have been published by national societies, but no Spanish national guidelines for management of these patients have been published. More importantly, national clinical practice regarding these patients is not standardised., Materials and Methods: Members of the Spanish Breast Cancer Radiation Oncology Group (GEORM in Spanish) were surveyed through an online questionnaire on behalf of the Spanish radiation oncology departments., Results: Only 39.3% of the Spanish radiation oncology departments have policies aimed at CIED carrier patients. Regardless of that, 96.4% of those who responded to the survey refer these patients to their Cardiology department before the start of the course of radiotherapy, and 17.8% of respondents said to manipulate the CIED without any cardiology department direction. A wide range of responses was obtained related to concepts such as "distance from the irradiation field to the CIED" or "safe accumulated doses"., Conclusions: Our results demonstrate the need for national guidelines for CIED patients and the need to promote educational activities addressed to standardise clinical management of these patients in the radiation oncology departments.

Objective: A safety threshold for baseline rhythm R-wave amplitudes during follow-up of implantable cardioverter defibrillators (ICD) has not been established. We aimed to analyse the amplitude distribution and undersensing rate during spontaneous episodes of ventricular fibrillation (VF), and define a safety amplitude threshold for baseline R-waves., Methods: Data were obtained from an observational multicentre registry conducted at 48 centres in Spain. Baseline R-wave amplitudes and VF events were prospectively registered by remote monitoring. Signal processing algorithms were used to compare amplitudes of baseline R-waves with VF R-waves. All undersensed R-waves after the blanking period (120 ms) were manually marked., Results: We studied 2507 patients from August 2011 to September 2014, which yielded 229 VF episodes (cycle length 189.6±29.1 ms) from 83 patients that were suitable for R-wave comparisons (follow-up 2.7±2.6 years). The majority (77.6%) of VF R-waves (n=13953) showed lower amplitudes than the reference baseline R-wave. The decrease in VF amplitude was progressively attenuated among subgroups of baseline R-wave amplitude (≥17; ≥12 to <17; ≥7 to <12; ≥2.2 to <7 mV) from the highest to the lowest: median deviations -51.2% to +22.4%, respectively (p=0.027). There were no significant differences in undersensing rates of VF R-waves among subgroups. Both the normalised histogram distribution and the undersensing risk function obtained from the ≥2.2 to <7 mV subgroup enabled the prediction that baseline R-wave amplitudes ≤2.5 mV (interquartile range: 2.3-2.8 mV) may lead to ≥25% of undersensed VF R-waves., Conclusions: Baseline R-wave amplitudes ≤2.5 mV during follow-up of patients with ICDs may lead to high risk of delayed detection of VF., Trial Registration Number: NCT01561144; results., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)