In contrast to textbook declaratory presentations, expla- nations were supplemented with evidence tables. The GWC also provided a brief summary of the relevant recommenda- tions and references related to secondary prevention rather than detailed reiteration. Throughout, the goal was to provide the clinician with concise, evidence-based contemporary rec- ommendations and the supporting documentation to encour- age their application. 2. Overview Of ACS 2.1. Definition of Terms ACS has evolved as a useful operational term that refers to a spectrum of conditions compatible with acute myocar- dial ischemia and/or infarction that are usually due to an abrupt reduction in coronary blood flow (Figure 1). A key branch point is ST-segment elevation (ST-elevation) or new left bundle-branch block on the electrocardiogram (ECG), which is an indication for immediate coronary angiography to determine if there is an indication for reperfusion ther- apy to open a likely completely occluded coronary artery. Separate CPGs have been developed for ST-elevation myo- cardial infarction (STEMI).17 TheabsenceofpersistentST-elevationissuggestiveofNSTE- ACS (except in patients with true posterior myocardial infarc- tion [MI], Sections 3.3.2.4, 4.3.2, and 7.2.2). NSTE-ACS can be further subdivided on the basis of cardiac biomarkers of necro- sis (eg, cardiac troponin, Sections 3.2.4 and 3.4). If cardiac bio- markers are elevated and the clinical context is appropriate, the patient is considered to have NSTEMI34 ; otherwise, the patient is deemed to have UA. ST depression, transient ST-elevation, and/or prominent T-wave inversions may be present but are not required for a diagnosis of NSTEMI. Abnormalities on the ECG and elevated troponins in isolation are insufficient to make the diagnosis of ACS but must be interpreted in the appropri- ate clinical context. Thus, UA and NSTEMI are closely related conditions whose pathogenesis and clinical presentations are similar but vary in severity. 