The following are key points to remember from this review article, which compares and contrasts the American and European guidelines on non–ST-segment elevation acute coronary syndromes (NSTE-ACS):

1. NSTE-ACS are the leading cause of morbidity and mortality from cardiovascular disease worldwide.
2. The American Heart Association/American College of Cardiology (AHA/ACC) 2014 update and the European Society of Cardiology (ESC) 2015 NSTE-ACS recommendations both emphasize the importance of early evaluation by the emergency department, a clinical history, physical examination, and 12-lead electrocardiogram within 10 minutes of a patient’s arrival.
3. Both guidelines also stress the growing importance of biomarkers, namely high-sensitivity cardiac troponin (hs-cTN) assays, due to their high negative predictive value for ACS. In particular, the ESC guidelines recommend utilizing a shortened algorithm for diagnosis of NSTE-ACS, with the use of a 0 hour/3 hour or 0 hour/1 hour algorithm measurement of hs-cTN.
4. In patients with suspected NSTE-ACS without recurrence of chest pain and with normal levels of cardiac troponin, the ESC guidelines recommend a noninvasive stress test with imaging to look for inducible ischemia (Class of Recommendation [COR] I, Level of Evidence [LOE] A) before deciding on an invasive strategy. In contrast, the AHA/ACC guidelines provide a lower strength of recommendation (COR IIa) to proceeding with a treadmill electrocardiogram, stress myocardial perfusion imaging, or coronary computed tomography angiography for patients with symptoms concerning for ACS, but without objective signs.
5. For those who undergo coronary revascularization, the ESC guidelines specifically recommend the radial approach for vascular access (COR I, LOE A), whereas the AHA/ACC guidelines do not provide any specific recommendations on the preferred vascular access site.
6. Both the ESC and AHA/ACC guidelines recommend the “heart team” approach to revascularization decisions regarding percutaneous coronary intervention (PCI) versus coronary artery bypass grafting.
7. The AHA/ACC guidelines recommend either clopidogrel or ticagrelor loading for either the invasive or ischemia-guided options, with a COR IIa, LOE B recommendation for ticagrelor over clopidogrel. The guidelines recommend prasugrel when a PCI is planned in those not at high risk of bleeding. The ESC guidelines make several recommendations regarding the specific choice of P2Y12 inhibitors. These preferences include ticagrelor for patients at moderate to high ischemic risk (COR I, LOE B), prasugrel for planned PCI after delineation of coronary anatomy (COR I, LOE B), and clopidogrel as second-line therapy if other drugs are contraindicated or are not options (COR I, LOE B).
8. The ESC guidelines underscore the importance of treating both sexes presenting with NSTE-ACS in the same way (COR I, LOE B). The AHA/ACC guidelines state that women with low-risk features should not undergo early invasive treatment because of the potential for harm (COR III, LOE B) on the basis of the evidence that women had higher bleeding complications and contrast-induced nephropathy in analyses of recent trials.
9. The ESC guidelines recommend international normalized ratios (INRs) of 2.0-2.5 when using warfarin during treatment with dual antiplatelet therapy, and avoidance of prasugrel or ticagrelor as part of triple therapy. In contrast, the AHA/ACC guidelines state that there is insufficient evidence to target this lower INR range.
10. Clinical guidelines are systematic statements to help guide clinical practices and are updated periodically, typically every 2-5 years. New approaches are necessary to rapidly integrate new information more quickly and efficiently. Mini-updates, specific modifications, or clarifications of individual recommendations may need to be considered as ongoing results from clinical trials are reported.

Keywords: Acute Coronary Syndrome, Angiography, Biomarkers, Chest Pain, Coronary Artery Bypass, Electrocardiography, Emergency Service, Hospital, Exercise Test, International Normalized Ratio, Ischemia, Myocardial Perfusion Imaging, Myocardial Revascularization, Percutaneous Coronary Intervention, Platelet Aggregation Inhibitors, Practice Guideline, Tomography, Troponin, Warfarin

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