Pad size, orientation, and placement for defibrillation during basic life support: A systematic review

Aim: To evaluate the impact of defibrillation pad size, orientation, and position on clinical outcomes in adult and paediatric cardiac arrest with a shockable rhythm through a systematic review of available evidence. Methods: A systematic review was registered with PROSPERO (CRD42024512443). Searches were performed across PubMed, EMBASE, and the Cochrane Library up to March 31st, 2025. Studies involving adults or children with cardiac arrest and comparing pad sizes or positions were included. Risk of bias was assessed using the RoB 2.0 and ROBINS-I tools, and the certainty of evidence was evaluated using GRADE methodology. Results: Of 7855 screened studies, four met inclusion criteria, e.g. 1 randomized clinical trial (RCT) and 3 observational studies in adults, covering 1334 adult cardiac arrest patients. Evidence on pad size, deriving from an observational study enrolling 314 patients, was sparse and inconclusive, with no significant differences in defibrillation success between large and small pads (OR 0.82[0.42-1.60]). For pad orientation, no evidence was found. For pad placement, one RCT including 280 patients suggested a potential survival benefit from vector-change defibrillation using anterior-posterior (AP) pad placement in refractory ventricular fibrillation (VF), compared to the standard anterior-lateral (AL) placement (adj. RR 1.71[1.01-2.88]). Data from two observational studies including 739 patients were conflicting and limited by high risk of bias. Conclusion: Evidence remains inconclusive to support the superiority of any specific pad size, orientation or position for improving survival or neurological outcomes in cardiac arrest. However, vector-change to the AP position may offer benefit in cases of refractory VF. High-quality RCTs are needed to further inform clinical practice.