Acute Coronary Syndrome: Comprehensive Teaching Presentation for NEET SS
Slide 1: 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, 2
- NSTE-ACS (70% of ACS): No persistent ST-elevation; includes NSTEMI (elevated troponin) and unstable angina (normal troponin) 1, 2
- ECG patterns in NSTE-ACS: ST-depression ≥0.5 mm (31%), T-wave inversion >1 mm (12%), both combined (16%), or normal ECG (41%) 1, 2
Slide 2: Pathophysiology - The Core Mechanism
Type 1 MI results from atherosclerotic plaque rupture or erosion exposing thrombogenic material, triggering platelet activation and thrombus formation that obstructs coronary flow. 1
- Plaque progression: Normal artery → lipid accumulation → fibrofatty plaque → thin-cap fibroatheroma with procoagulant expression → fibrous cap disruption → thrombogenesis 1
- Vulnerable plaque characteristics: Thin fibrous cap, large lipid core, active inflammation, small luminal area despite angiographically mild appearance 1
- Thrombosis patterns: Complete occlusion (STEMI) vs. partial/intermittent occlusion (NSTE-ACS) with possible distal microembolization 1
- Alternative mechanisms (less common): Coronary spasm, embolism, dissection, supply-demand mismatch without plaque rupture 1
Slide 3: Epidemiology and Risk Factors
Over 7 million people worldwide and >780,000 Americans experience ACS annually, with NSTE-ACS comprising 70% of cases. 1, 2
- Traditional risk factors: Age ≥65 years, current smoking, hypertension, diabetes mellitus, hyperlipidemia, BMI >25 kg/m², family history of premature CAD 3
- Diabetes: Stronger risk factor in women than men 4
- NSTE-ACS patients: Typically older with more comorbidities (cardiac and non-cardiac) than STEMI patients 1
- 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 1
Slide 4: Clinical Presentation - Typical Features
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, 2
- Chest discomfort descriptors: Pressure, oppression, heaviness, crushing, cramping, burning, aching—NOT sharp or stabbing 1, 5
- Radiation patterns: Left arm (most common), right arm, both arms, neck, jaw, shoulders, back 4, 5, 6
- Associated symptoms: Diaphoresis (95% specificity when combined with typical pain, LR 5.18), dyspnea, nausea/vomiting 4, 6
- Prolonged pain (>20 minutes) in 80%; de novo or accelerated angina in 20% 1
Slide 5: Clinical Presentation - Atypical Features (High-Yield for NEET SS)
Approximately 40% of men and 48% of women present with atypical symptoms, creating diagnostic challenges that lead to delayed treatment and worse outcomes. 4, 2
- Women-specific presentations: Epigastric pain, unexplained indigestion, persistent dyspnea, back pain, jaw pain (10% vs. 4% in men), fatigue, nausea without chest pain 4
- Elderly patients (>75 years): Generalized weakness, syncope, stroke, altered mental status, isolated dyspnea 4, 5
- Diabetic patients: Atypical presentations due to autonomic dysfunction, may lack typical pain 4, 5
- Critical pitfall: Atypical presentations lead to underrecognition, delayed ECG, and undertreatment—never dismiss epigastric or jaw pain without cardiac workup in high-risk populations 4
Slide 6: Initial Assessment - The 10-Minute Rule
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, 5
- Two fundamental questions: (1) What is the likelihood of ACS? (2) What is the likelihood of adverse outcomes? 1
- Immediate actions: Place patient in monitored environment with defibrillation capability, obtain IV access, administer oxygen if SpO₂ <90% or respiratory distress 1, 5
- Aspirin 162-325 mg immediately unless contraindicated or already taken 5
- Sublingual nitroglycerin (up to 3 doses, 5 minutes apart) if SBP >90 mmHg 5
- Critical error: Never evaluate suspected ACS by telephone—requires facility-based assessment with ECG and biomarkers 6
Slide 7: ECG Interpretation - STEMI Criteria
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
- Contiguous lead groups: Anterior (V1-V4), lateral (I, aVL, V5-V6), inferior (II, III, aVF), right ventricular (V3R-V4R) 1
- Obtain V3R-V4R leads in inferior STEMI to detect RV infarction (affects hemodynamic management) 1
Slide 8: ECG Interpretation - NSTE-ACS Patterns
Horizontal or downsloping ST-depression ≥0.5 mm in ≥2 contiguous leads and/or T-wave inversion >1 mm with prominent R wave (R/S >1) indicates high-risk NSTE-ACS. 1
- Dynamic changes: Transient ST-elevation, ST-depression that resolves, T-wave changes that evolve 1
- High-risk features: ST-depression ≥2 mm, widespread ST-depression, ST-depression in V1-V4 (suggests posterior or multivessel disease) 1
- Normal ECG does NOT exclude ACS: 41% of NSTE-ACS patients have non-diagnostic initial ECG 2
- Serial ECGs: Repeat every 15-30 minutes if initial ECG non-diagnostic but symptoms persist 1
Slide 9: Cardiac Biomarkers - High-Sensitivity Troponin
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. 1, 6
- 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 1
- Timing protocol: Draw at presentation (0 hours) and repeat at 1-2 hours using rapid rule-in/rule-out algorithms 5, 6
- Do NOT wait for troponin results before initiating reperfusion therapy if STEMI present on ECG 5
- Troponin distinguishes NSTEMI from unstable angina: Elevated = NSTEMI, normal = unstable angina 1
Slide 10: Risk Stratification Tools
TIMI, GRACE, and HEART scores predict adverse outcomes and guide management intensity, though no tool replaces clinical judgment in high-risk presentations. 1, 7
- 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 1
- GRACE score: More complex but better long-term mortality prediction; includes age, heart rate, SBP, creatinine, Killip class, cardiac arrest, ST-deviation, elevated biomarkers 1
- HEART score: History (0-2), ECG (0-2), Age (0-2), Risk factors (0-2), Troponin (0-2); score ≥4 warrants admission 7
- Limitations: Risk scores may underestimate risk in women and misclassify them as having non-ischemic pain 4
Slide 11: Immediate Medical Management - STEMI
Primary PCI within 90-120 minutes of first medical contact is the preferred reperfusion strategy for STEMI, reducing mortality from 9% to 7%. 1, 2
- If PCI unavailable within 120 minutes: Fibrinolytic therapy with alteplase, reteplase, or tenecteplase (full dose if <75y, half dose if ≥75y), followed by transfer for PCI within 24 hours 2
- Antiplatelet therapy: Aspirin 162-325 mg loading dose + P2Y₁₂ inhibitor (prasugrel 60 mg, ticagrelor 180 mg, or clopidogrel 600 mg) 1, 8
- Anticoagulation: UFH, enoxaparin, or bivalirudin during PCI 1
- Adjunctive therapy: IV morphine 4-8 mg for pain (avoid IM), IV nitroglycerin if ongoing pain and SBP >90 mmHg, oxygen only if SpO₂ <90% 5
Slide 12: Immediate Medical Management - NSTE-ACS
High-risk NSTE-ACS patients require invasive coronary angiography within 24-48 hours, reducing mortality from 6.5% to 4.9%. 1, 2
- High-risk features mandating early invasive strategy: Elevated troponin, dynamic ST-changes, hemodynamic instability, recurrent/refractory ischemia, heart failure, life-threatening arrhythmias, recent PCI/CABG 1
- Dual antiplatelet therapy: Aspirin + P2Y₁₂ inhibitor (ticagrelor or prasugrel preferred over clopidogrel in invasive strategy) 1
- Anticoagulation: Fondaparinux, enoxaparin, or UFH; continue until revascularization 1
- Conservative strategy: For low-risk patients (TIMI 0-2, negative troponins, no high-risk features)—stress testing before discharge 1
Slide 13: Contraindications and Special Considerations
Active bleeding and prior TIA/stroke are absolute contraindications to fibrinolytic therapy; age >75 years and weight <60 kg require dose adjustments for antiplatelet agents. 8, 2
- Fibrinolytic contraindications: Active bleeding, history of intracranial hemorrhage, ischemic stroke within 3 months, suspected aortic dissection, significant closed head trauma within 3 months 2
- Prasugrel contraindications: Prior TIA/stroke (absolute), age ≥75y (relative—consider 5mg maintenance if used), weight <60kg (increased bleeding risk) 8
- CABG considerations: Discontinue P2Y₁₂ inhibitors 5-7 days before surgery (ticagrelor 5 days, clopidogrel 5 days, prasugrel 7 days) to reduce bleeding 1
- Women-specific: Higher bleeding risk with standard dosing—consider weight-based and renal function-based adjustments 4
Slide 14: Complications - Recognition and Management
Mechanical complications (papillary muscle rupture, ventricular septal defect, free wall rupture) and cardiogenic shock represent life-threatening emergencies requiring immediate recognition. 1
- Cardiogenic shock: Hypotension (SBP <90 mmHg), signs of hypoperfusion, pulmonary congestion; requires immediate angiography and revascularization, consider mechanical circulatory support 1
- Papillary muscle rupture: New holosystolic murmur with acute pulmonary edema, typically 3-5 days post-MI; requires urgent surgical repair 1
- Ventricular septal rupture: New harsh holosystolic murmur with thrill, hemodynamic deterioration; urgent surgical closure 1
- RV infarction (inferior STEMI): Hypotension, elevated JVP, clear lungs; avoid nitrates/diuretics, give IV fluids, maintain preload 1
- Arrhythmias: VF/VT (immediate defibrillation), complete heart block in inferior MI (usually transient), Mobitz II/CHB in anterior MI (requires pacing) 1
Slide 15: Secondary Prevention - Discharge Medications
All ACS patients require lifelong aspirin, high-intensity statin, beta-blocker, and ACE inhibitor/ARB unless contraindicated; P2Y₁₂ inhibitor for minimum 12 months. 1, 3
- 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
- Statin therapy: High-intensity (atorvastatin 40-80 mg or rosuvastatin 20-40 mg) regardless of baseline LDL, target LDL <70 mg/dL 3
- Beta-blocker: Metoprolol, carvedilol, or bisoprolol; continue indefinitely if LV dysfunction, otherwise minimum 3 years 3
- ACE inhibitor/ARB: Especially if LV dysfunction (EF <40%), diabetes, hypertension, or anterior MI 3
- SGLT-2 inhibitor: Reduces mortality in patients with diabetes or heart failure post-MI 3
Slide 16: Additional Mortality-Reducing Interventions
Smoking cessation, annual influenza vaccination, and cardiac rehabilitation participation each independently reduce post-MI mortality and must be prescribed at discharge. 3
- Smoking cessation: Single most important modifiable risk factor; provide pharmacotherapy (varenicline, bupropion, or nicotine replacement) plus counseling 3
- Cardiac rehabilitation: 36 sessions over 12 weeks; reduces mortality by 20-30%, improves functional capacity, addresses psychosocial factors 3
- Influenza vaccination: Annual vaccination reduces cardiovascular events and mortality in CAD patients 3
- Lifestyle modifications: Mediterranean diet, regular aerobic exercise (150 min/week moderate intensity), weight loss if BMI >25 kg/m² 3
Slide 17: Sex-Specific Considerations (High-Yield)
Women with ACS are 8-10 years older than men, present with more atypical symptoms, have higher rates of non-obstructive CAD, yet receive less guideline-directed care and have worse outcomes. 4
- Pathophysiology differences: Women have higher proportion of plaque erosion (vs. rupture), coronary microvascular dysfunction, spontaneous coronary artery dissection, and Takotsubo cardiomyopathy 4
- Presentation differences: More likely to have nausea, back pain, jaw pain, fatigue; describe chest pain as "pressure/tightness" rather than "crushing" 4
- Pregnancy-related risk: History of preeclampsia or gestational hypertension increases lifetime CVD risk but is rarely assessed 4
- Treatment disparities: Women less likely to receive timely angiography, PCI, and guideline-directed medications despite similar or higher risk 4
- Outcomes: Younger women (<50y) have significantly higher long-term mortality than younger men despite similar in-hospital mortality 4
Slide 18: Common Pitfalls to Avoid
- Never dismiss atypical presentations (epigastric pain, jaw pain, dyspnea alone) in elderly, women, or diabetics without full ACS workup including ECG and troponin 4, 5
- Never delay ECG beyond 10 minutes of presentation—this is the most critical time-dependent diagnostic test 5, 6
- Never wait for troponin results before initiating reperfusion therapy in STEMI 5
- Never use nitroglycerin response as a diagnostic criterion—relief with NTG does not confirm or exclude ACS 4
- Never give nitrates or diuretics in RV infarction (inferior STEMI with ST-elevation in V3R-V4R)—causes catastrophic hypotension 1
- Never evaluate suspected ACS by telephone—requires in-person assessment with monitoring, ECG, and biomarkers 6
- Never assume normal initial ECG excludes ACS—41% of NSTE-ACS have non-diagnostic initial ECG; obtain serial ECGs 2
- Never discharge patients with ongoing symptoms even if initial workup negative—consider provocative testing or prolonged observation 7