OBJECTIVETo define the association between time taken to present to the emergency department (ED) with symptoms of possible acute coronary syndrome (ACS) and 1-year outcomes. We also determined whether particular patient characteristics are associated with delays in seeking care after symptom onset.METHODSWe collected data, which included a customised case report form to record symptom onset, on adult patients presenting with suspected ACS to two EDs in Australia and New Zealand. Such patients were followed up prospectively for 1 year. The composite primary endpoint included death, acute myocardial infarction, unstable angina pectoris treated with revascularisation or readmission with heart failure occurring after discharge but within 12 months after the index presentation.RESULTSACS was diagnosed at presentation in 420 (16.8%) of 2515 patients recruited. Cox regression was conducted to assess the relationship between presentation time and the rate of primary endpoints after controlling for age, ethnicity, prior angina, prior coronary artery bypass graft and index diagnosis. Middle (2-6 h) and late presenters (>6 h postsymptom onset) developed the primary endpoint at a rate 1.22 (95% CI 0.80 to 1.85) and 1.57 (1.07 to 2.31) times higher than early presenters. Patients with known risk factors and cardiovascular disease were more likely to present late to the ED.CONCLUSIONSThere is an independent association between time to presentation and 1-year cardiac outcomes following initial chest pain assessment for ED patients with possible cardiac chest pain in the Australian and New Zealand setting. This association occurred irrespective of the eventual diagnosis. Effective public health campaigns and other measures that facilitate early presentation with symptoms for patients with symptoms suggestive of ACS are justified and may improve prognosis.TRIAL REGISTRATION NUMBERACTRN12611001069943.