Acute Coronary Syndrome Diagnosis and Management

Definition and Classification

Acute Coronary Syndrome encompasses three clinical entities along a continuum: unstable angina, NSTEMI, and STEMI, all resulting from atherosclerotic plaque disruption with subsequent thrombosis causing myocardial oxygen supply-demand mismatch 1
STEMI (30% of ACS): Persistent ST-elevation ≥1 mm in ≥2 contiguous leads (≥2 mm in V2-V3 for men ≥40y, ≥2.5 mm for men <40y, ≥1.5 mm for women), reflecting complete coronary occlusion with transmural ischemia 1
NSTE-ACS (70% of ACS): No persistent ST-elevation; includes NSTEMI (elevated troponin) and unstable angina (normal troponin) 2

Type 1 MI results from atherosclerotic plaque rupture or erosion exposing thrombogenic material, triggering platelet activation and thrombus formation that obstructs coronary flow 3, 1
Plaque progression: Normal artery → lipid accumulation → fibrofatty plaque → thin-cap fibroatheroma with procoagulant expression → fibrous cap disruption → thrombogenesis 2, 4
Vulnerable plaque characteristics: Thin fibrous cap, large lipid core, active inflammation, small luminal area despite angiographically mild appearance 5

Over 7 million people worldwide and >780,000 Americans experience ACS annually, with NSTE-ACS comprising 70% of cases 2
Diabetes: Stronger risk factor in women than men 7
NSTE-ACS patients: Typically older with more comorbidities (cardiac and non-cardiac) than STEMI patients 2
Mortality patterns: Hospital mortality higher in STEMI (7%) vs. NSTE-ACS (3-5%), but 6-month mortality similar (12-13%); long-term mortality higher in NSTE-ACS due to older age and comorbidities 5

Retrosternal chest pressure, heaviness, or tightness lasting >20 minutes and radiating to left arm, neck, or jaw represents the classic ACS presentation in 79% of men and 74% of women 1
Chest discomfort descriptors: Pressure, oppression, heaviness, crushing, cramping, burning, aching—NOT sharp or stabbing 5, 8
Radiation patterns: Left arm (most common), right arm, both arms, neck, jaw, shoulders, back 7, 8, 9
Associated symptoms: Diaphoresis (95% specificity when combined with typical pain, LR 5.18), dyspnea, nausea/vomiting 7, 9

Obtain 12-lead ECG within 10 minutes of presentation in all patients with suspected ACS—this is the single most critical time-dependent intervention for diagnosis and triage 1, 4, 8
Two fundamental questions: (1) What is the likelihood of ACS? (2) What is the likelihood of adverse outcomes? 2, 4
Immediate actions: Place patient in monitored environment with defibrillation capability, obtain IV access, administer oxygen if SpO₂ <90% or respiratory distress 4, 8

New ST-elevation ≥1 mm in ≥2 anatomically contiguous leads (except V2-V3) or new LBBB with clinical context mandates immediate reperfusion therapy 1
V2-V3 criteria (age/sex-specific): ≥2 mm (men ≥40y), ≥2.5 mm (men <40y), ≥1.5 mm (women) 1
STEMI equivalents: New or presumed new LBBB, posterior MI (tall R waves V1-V2 with ST-depression), de Winter T-waves 1

High-sensitivity cardiac troponin (hs-cTn) T or I >99th percentile upper reference limit with rising/falling pattern confirms myocardial infarction when combined with clinical context 3, 9
Universal MI definition requires: Elevated troponin PLUS at least one of: (1) ischemic symptoms, (2) new ischemic ECG changes, (3) pathological Q waves, (4) imaging evidence of new myocardial loss, (5) intracoronary thrombus on angiography 3

TIMI, GRACE, and HEART scores predict adverse outcomes and guide management intensity, though no tool replaces clinical judgment in high-risk presentations 4
TIMI score (0-7 points): Age ≥65, ≥3 CAD risk factors, known CAD (stenosis ≥50%), aspirin use in past 7 days, ≥2 anginal episodes in 24h, ST-deviation ≥0.5mm, elevated cardiac markers 4
GRACE score: More complex but better long-term mortality prediction; includes age, heart rate, SBP, creatinine, Killip class, cardiac arrest, ST-deviation, elevated biomarkers 4

Primary PCI within 90-120 minutes of first medical contact is the preferred reperfusion strategy for STEMI, reducing mortality from 9% to 7% 1
Antiplatelet therapy: Aspirin 162-325 mg loading dose + P2Y₁₂ inhibitor (prasugrel 60 mg, ticagrelor 180 mg, or clopidogrel 600 mg) 1
Anticoagulation: UFH, enoxaparin, or bivalirudin during PCI 1

Mechanical complications (papillary muscle rupture, ventricular septal defect, free wall rupture) and cardiogenic shock represent life-threatening emergencies requiring immediate recognition 3, 10
Cardiogenic shock: Hypotension (SBP <90 mmHg), signs of hypoperfusion, pulmonary congestion; requires immediate angiography and revascularization, consider mechanical circulatory support 3
Papillary muscle rupture: New holosystolic murmur with acute pulmonary edema, typically 3-5 days post-MI; requires urgent surgical repair 10

All ACS patients require lifelong aspirin, high-intensity statin, beta-blocker, and ACE inhibitor/ARB unless contraindicated; P2Y₁₂ inhibitor for minimum 12 months 1
Dual antiplatelet therapy: Aspirin 81 mg daily + P2Y₁₂ inhibitor (ticagrelor 90 mg BID or prasugrel 10 mg daily preferred over clopidogrel 75 mg daily) for 12 months minimum 1