Acute Coronary Syndrome (ACS) encompasses a spectrum of conditions caused by reduced blood flow in the coronary arteries, including unstable angina and myocardial infarction (MI). It is typically diagnosed through a patient's symptoms, electrocardiogram (ECG) findings, and cardiac biomarker levels. For ACS patients presenting within 12 hours of symptoms, guidelines recommend obtaining an ECG within 10 minutes and starting reperfusion therapies like thrombolysis within 30 minutes to minimize heart muscle damage. Diagnosis is based on criteria including typical chest pain, ECG changes, and elevated troponin levels. Outcomes are generally worse in elderly patients and those with atypical presentations and longer treatment delays.