Acute coronary syndromes remain a public health concern that has a negative impact on the quality of life of thousands of patients worldwide and represents an important economic burden for health-care systems. To reduce ACS morbidity and mortality in the emergency room (ER), an expedite and accurate diagnosis of acute ischemic heart disease is mandatory. Rapid identification of coronary syndromes leads to prompt and optimal treatment, therefore reducing the burden of chronic disease if patients achieve revascularization within an optimal time frame. Early recognition of ECG changes and use of chest pain scores can reduce delays to treatment and improve clinical outcomes for acute myocardial infarction patients and other medical emergencies. This chapter summarizes ACS pathology, classification, clinical presentation, risk stratification, biomarker use, imaging modalities, as well as the most universally accepted diagnostic and therapeutic strategies.