Variation in prehospital ACS care within a single city: a bicentric observational study (MONAH-1 subgroup analysis)

Abstract Background Acute coronary syndrome (ACS) is a time-critical medical emergency in which early guideline-based prehospital diagnosis and treatment are crucial for the subsequent care pathway. The aim of this study was to compare documented adherence to selected prehospital ACS process indicators between two provider structures operating within the same municipal EMS system. Methods As part of the retrospective, bicentric observational study MONAH-1, all prehospital physician missions with typical ACS diagnoses in Magdeburg between 2014 and 2018 were analysed. This prespecified intra-urban subgroup analysis compared one EMS physician base staffed by MD1 with two EMS physician bases staffed by MD2. Because case retrieval was diagnosis-targeted from archived protocols rather than based on a prospectively maintained screening registry, a full flow diagram of all EMS missions could not be reconstructed reliably; endpoint-specific denominators are therefore reported in the text and tables. Multivariable analyses were adjusted for age and gender only and should be interpreted as partially adjusted exploratory models. Results A total of 1,438 emergency physician interventions were evaluated (MD1: n = 661; MD2: n = 777). MD1 showed documented higher rates of 12-lead ECGs (76.9% vs. 43.5%; aOR 4.24 95% CI 3.36–5.35), ASA administration (91.4% vs. 70.9%; aOR 4.38 3.19–6.00) and heparin administration (92.6% vs. 68.0%; aOR 5.86 4.21–8.16). In the descriptive indication-positive subgroup with documented VAS ≥ 4, morphine was documented more often at MD1 (70.6% vs. 54.5%); the exploratory adjusted morphine model was based on missions with documented pain assessment (aOR 2.67 2.04–3.50). No significant differences were found for indication-based nitro-glycerine and oxygen administration. Prehospital dwell time was longer at MD1 (median 34 vs. 29 min; p < 0.001). Conclusion Documented adherence to selected prehospital ACS process indicators differed between the two providers. MD1 showed higher documented rates for several process measures, but the retrospective design, heterogeneous documentation formats, limited case-mix adjustment, and the possibility of reverse causation for dwell time preclude causal inference or conclusions about patient benefit. The findings are hypothesis-generating and primarily relevant for local quality assurance and prospective validation. Trial registration The study was registered retrospectively in the German Clinical Trials Register (DRKS00036944) on 27 August 2025.