Acute Coronary Syndrome Management

Introduction

• Acute Coronary Syndrome (ACS) includes three distinct clinical conditions: unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI), typically caused by disruption of an unstable coronary artery atherosclerotic plaque with associated partial or complete coronary artery thrombosis and/or microemboli, resulting in diminished blood flow to the myocardium and subsequent myocardial ischemia, as defined by the American Heart Association and American College of Cardiology 1, 2, 3, 4

Diagnosis and Risk Assessment

• The distinction between unstable angina (UA) and non-ST-elevation myocardial infarction (NSTEMI) is primarily based on whether ischemia is severe enough to cause myocardial damage with detectable quantities of cardiac injury biomarkers, most commonly troponin, according to the American Heart Association 1
• High-risk features for NSTEMI include recurrent angina, hemodynamic instability, heart failure, life-threatening arrhythmias, and dynamic ST-segment changes, as identified by the American College of Cardiology 1
• Risk assessment tools such as TIMI, PURSUIT, GRACE, and NCDR-ACTION scores help predict outcomes in patients with NSTEMI, as recommended by the American Heart Association 1
• The initial diagnosis and classification of ACS should be based on clinical history and symptoms, ECG findings, and cardiac biomarkers, as recommended by the American Heart Association and American College of Cardiology 5, 6, 7, 8
• ECG findings for NSTE-ACS include new or presumed new horizontal or down-sloping ST-segment depression ≥0.5 mm in ≥2 contiguous leads and/or T-wave inversion >1 mm in ≥2 contiguous leads, while STEMI is characterized by new or presumed new ST-elevation of ≥1 mm in ≥2 anatomically contiguous leads, as stated by the American College of Cardiology 5
• Cardiac troponin (cTn) is the preferred biomarker for diagnosing ACS, and serial measurements may be necessary, according to the American Heart Association and American College of Cardiology 9, 6, 7, 8

Classification of Acute Coronary Syndrome

• Unstable angina is characterized by rest angina, new-onset severe angina, and increasing pattern of previously stable angina, often with transient ST-segment depression or T-wave changes on ECG, and normal cardiac biomarkers, as defined by the American Heart Association and American College of Cardiology 1, 4, 10, 5, 7, 11, 8
• NSTEMI is characterized by myocardial ischemia with evidence of myocardial necrosis, with clinical features including prolonged chest pain/discomfort, ECG shows ST-segment depression, T-wave inversion, or may be normal, and elevated cardiac biomarkers (troponin), as stated by the American College of Cardiology 1, 4, 10, 5
• STEMI is characterized by myocardial ischemia with evidence of myocardial necrosis, with clinical features including prolonged chest pain/discomfort, ECG shows persistent ST-segment elevation or new left bundle branch block, and elevated cardiac biomarkers (troponin), as defined by the American Heart Association and American College of Cardiology 1, 4, 10, 5
• The classification of ACS into UA, NSTEMI, and STEMI allows for appropriate risk stratification and guides evidence-based management strategies aimed at reducing morbidity and mortality, with the American College of Cardiology recommending immediate reperfusion therapy for STEMI and selection of antiplatelet and anticoagulant regimens based on the type of ACS 4

Comparison of Acute Coronary Syndrome Types

Comparison with Stable Angina

Treatment and Management

• The American Heart Association recommends anti-ischemic therapy, including oxygen if saturation <90%, nitrates for ongoing chest pain, beta-blockers (in absence of contraindications), and morphine for pain relief if needed, for patients with NSTEMI 1
• The European Society of Cardiology recommends an early invasive strategy (within 24-72 hours) for patients with hemodynamic instability, recurrent or ongoing chest pain despite medical therapy, dynamic ST-T wave changes, high-risk features on risk scores, or elevated cardiac biomarkers 1
• The American College of Cardiology recommends risk factor modification, including smoking cessation, blood pressure control, diabetes management, regular physical activity, and dietary modifications, for patients with NSTEMI 1, 12