Atypical presentation of ACS can range from non-chest pain to an epileptic seizure. Risk factors for atypical presentation include female gender, old age, comorbidities and severe mental illness. Troponin testing plays a central role when confronted with ACS but has only limited added-value with non-chest pain ACS. In cohort studies 1-2.2% of diagnosis of ACS is missed by emergency physicians. Possible explanations include atypical symptoms, non-diagnostic ECG and failure to interpret subtle ECG changes. ACS without chest pain frequently gets underdiagnosed and undertreated, which leads to more complications and a higher in-hospital mortality rate.