Those without ST-elevation have either UA or NSTEMI (thick red arrows), a distinction based on cardiac biomarkers. Most patients presenting with NSTEMI develop NQMI; a few may develop QwMI. The spectrum of clinical presentations including UA, NSTEMI, and STEMI is referred to as ACS. This NSTE-ACS CPG includes sections on initial management before NSTE-ACS, at the onset of NSTE-ACS, and during the hospital phase. Secondary prevention and plans for long-term management begin early during the hospital phase. Patients with noncardiac etiologies make up the largest group presenting to the ED with chest pain (dashed arrow). *Elevated cardiac biomarker (eg, troponin), Section 3.4. ACS indicates acute coronary syndrome; CPG, clinical practice guideline; Dx, diagnosis; ECG, electrocardiogram; ED, emergency department; Ml, myocardial infarction; NQMI, non-Q-wave myocardial infarction; NSTE-ACS, non-ST-elevation acute coronary syndromes; NSTEMI, non-ST-elevation myocardial infarction; QwMI, Q-wave myocardial infarction; STEMI, ST-elevation myocardial infarction; and UA, unstable angina. Modified with permission from Libby et al.38 outcome(s) to decide on the need for hospitalization and assist in the selection of treatment options.42 44 (Level of Evidence: B) Patients with suspected ACS must be evaluated rapidly to identify those with a life-threatening emergency versus those with a more benign condition. The goal of the initial evalua- tion focuses on answering 2 questions: 1. What is the likelihood that the symptoms and signs rep- resent ACS? 2. What is the likelihood of adverse clinical outcome(s)? Risk assessment scores and clinical prediction algorithms using clinical history, physical examination, ECG, and car- diac troponins have been developed to help identify patients with ACS at increased risk of adverse outcome(s). 