BackgroundSex‐based differences in clinical presentation, pathophysiology, and outcomes of patients with acute chest pain are increasingly being recognized, but are not implemented in guidelines and clinical prediction tools. We evaluated the performance of the HEART score in women versus men, because sex‐based differences may exist among the algorithm's components: history, electrocardiogram, age, risk factors, and admission troponin level.Methods and ResultsThe HEART score was retrospectively assessed in 831 women and 1084 men presenting to the emergency department with acute chest pain, assigning patients to the low‐, intermediate‐, or high‐risk category for the occurrence of major adverse cardiac events (MACE) within 6 weeks. MACE, consisting of myocardial infarction, coronary revascularization, and all‐cause death, also included events during index visit. Six‐week MACE rates were 2 times lower in women than men (10.0% versus 20.8%; P<0.01). Despite similar discriminatory accuracy of the HEART score among women and men (c‐statistic, 0.80 [0.75–0.84] versus 0.77 [0.74–0.81]; P=0.43), 6‐week MACE rates were significantly lower in women than men across all HEART risk categories: 2.1% versus 6.5% (P<0.01) in the low‐risk category, 12.7% versus 21.3% (P<0.01) in intermediate‐risk category, and 53.1% versus 77.0% (P=0.02) in the high‐risk category. The HEART score‐adjusted risk ratio for men was 1.6 (1.3–2.0; P<0.01).ConclusionsThe markedly higher 6‐week MACE risk in men across all HEART risk categories should be taken into account when using the HEART score to guide clinical decision making; early discharge with a low‐risk HEART score appears less safe for men than women with acute chest pain.