Patients with suspected ACS and high-risk features such as continuing chest pain, severe dyspnea, syn- cope/presyncope, or palpitations should be referred immediately to the ED and transported by emer- gency medical services when available. (Level of Evidence: C) Class IIb 1. Patients with less severe symptoms may be considered for referral to the ED, a chest pain unit, or a facility capable of performing adequate evaluation depend- ing on clinical circumstances. (Level of Evidence: C) Patients with suspected ACS and high-risk features should be transported to the ED by emergency medical services when available. Hospitals and outpatient facilities should provide clearly visible signage directing patients transported by pri- vate vehicle to the appropriate triage area. Outpatient facili- ties should have the capacity for ECG and cardiac troponin measurements with immediate ED referral for those consid- ered to have ACS. 3.2. Diagnosis of NSTE-ACS Differential diagnosis of NSTE-ACS includes41 : Nonischemic cardiovascular causes of chest pain (eg, aortic dissection, expanding aortic aneurysm, pericardi- tis, pulmonary embolism) Noncardiovascular causes of chest, back, or upper abdominal discomfort include: Pulmonary causes (eg, pneumonia, pleuritis, pneumothorax) Gastrointestinal causes (eg, gastroesophageal reflux, esophageal spasm, peptic ulcer, pancreatitis, biliary disease) Musculoskeletal causes (eg, costochondritis, cervical radiculopathy) Psychiatric disorders Other etiologies (eg, sickle cell crisis, herpes zoster) In addition, the clinician should differentiate NSTE-ACS from acute coronary insufficiency due to a nonatherosclerotic cause and noncoronary causes of myocardial oxygen supply- (Section 2.2.2). NSTE-ACS most commonly presents as a pressure-type chest pain that typically occurs at rest or with minimal exertion The pain most frequently starts in the retrosternal area and can radiate to either or both arms, the neck, or the jaw. Pain may also occur in these areas indepen- dent of chest pain. 