BackgroundThe PRAETORIAN score is developed as an alternative for defibrillation testing(DFT) post subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation, and assess three aspects of implant position on a bidirectional chest X-ray. The score is validated on a standard standing chest X-ray with arms elevated in the lateral view. ObjectiveWe aim to evaluate the effect of different anatomical positions on the PRAETORIAN score. MethodsThirty S-ICD patients underwent standard posterior-anterior (PA) and lateral chest X-rays, including additional lateral views in two positions: standing with arms down and supine with arms alongside the body. PRAETORIAN score and weighted kappa coefficient were calculated for each position. ResultsIn 8 out of 30 patients the PRAETORIAN score was ≥90 in standard position. The agreement in PRAETORIAN score was substantial (κ=0.677) for the position with the arms down and fair (κ =0.399) for the supine position. In 10 patients (33%) with the arms down the PRAETORIAN score decreased, of whom 4 changed to a lower risk category. In 16 patients (53%) the PRAETORIAN score decreased in supine position, of whom 7 changed to a lower risk category of which one patient changed from high to low risk. ConclusionA supine or arms-down position during chest X-rays can result in lower PRAETORIAN scores and underestimation of associated risk on DFT failure. This emphasizes the importance of correct anatomical positioning (‘arms up’) during chest X-rays when using the PRAETORIAN score.