Sex-Based Differences in Clinical Presentation, Management, and Outcomes of Acute Coronary Syndrome in Brazilian Emergency Medical Services

Background: Sex-related disparities in acute coronary syndrome (ACS) recognition and management remain a global health concern. We examined sex-based differences in clinical presentation, management, and outcomes among patients with chest pain attended by emergency medical services (EMS) across Brazil. Methods: We conducted a retrospective study using a registry from 14 Brazilian states between January 2020 and June 2024 within a private hospital network. Patients with chest pain were classified by cardiologists as unstable angina (UA), ST-elevation myocardial infarction (STEMI), or non-ST-elevation myocardial infarction (NSTEMI). Multivariable regression evaluated sex differences in diagnosis, treatment, and outcomes. Sensitivity analyses included state-clustered standard errors and E-values for unmeasured confounding. Results: Among 7,171 patients with confirmed ACS (68.2% male), median age was 63.0 years [IQR 20.0]; women were older than men (67.0 [20.0] vs 61.0 [19.0] years). Diagnoses were UA in 46.7%, STEMI in 18.8%, and NSTEMI in 34.6%. Overall, 91.7% received aspirin and 89.6% at least one additional antiplatelet agent. After adjustment, women had higher odds of chest pain classified as probably or possibly ischemic versus definitely ischemic (adjusted OR 1.51 [95% CI 1.33-1.72] and 1.60 [1.37-1.86], respectively) and lower odds of STEMI and NSTEMI relative to UA (adjusted OR 0.59 [0.51-0.68] and 0.74 [0.66-0.83], respectively). Door-to-ECG time was longer in women unadjusted ({beta}=1.53 minutes [0.24-2.82]) but not after adjustment ({beta}=1.04 [-0.27 to 2.36]). In-hospital mortality did not differ between sexes, with no evidence of excess short-term mortality in women. Conclusions: Within a private hospital network in Brazil, women with confirmed ACS were more often classified with less definitely ischemic chest pain and less frequently with STEMI or NSTEMI than men. Door-to-ECG differences did not persist after adjustment, and mortality did not differ by sex. These findings support sex-sensitive triage and diagnostic protocols to reduce inequities in ACS recognition and treatment.