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ACUTE CORONARY SYNDROME (ACS) - Complete EMD Exam Guide

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1. DEFINITION & CLASSIFICATION

• Frameworks for Internal Medicine, p. 33-34

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2. PATHOPHYSIOLOGY

• Stent thrombosis - in patients who recently underwent PCI
• Coronary artery embolism - traveling clot
• Coronary artery vasospasm - including Prinzmetal (variant) angina
  • Provoked by: cocaine, amphetamines, marijuana, 5-fluorouracil, sumatriptan
  • Active smokers constitute the majority of spontaneous vasospasm cases
• Type 2 MI - supply/demand mismatch (anemia, tachycardia, hypotension)

• Large lipid core
• Thin fibrous cap
• High macrophage/foam cell content
• Low smooth muscle content
• Frameworks for Internal Medicine, p. 34

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3. CLINICAL PRESENTATION

Typical Symptoms

• Substernal chest pain/pressure/heaviness
• Radiation to upper extremity, jaw, or epigastrium
• Duration typically >20 minutes
• Associated: diaphoresis, nausea, syncope

Atypical Presentations (MEMORIZE - exam favorite)

• Dyspnea (especially in women and elderly)
• Fatigue, weakness
• Abdominal pain (especially in women >65)
• Delirium/altered mental status (elderly)
• Back or shoulder pain

• Women - most likely to present with atypical symptoms
• Diabetics - autonomic neuropathy blunts pain
• Elderly - classic chest pain occurs in only ~50% of patients ≥85 years
• Post-operative patients

• Rosen's Emergency Medicine, p. 4015-4017

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4. ECG INTERPRETATION

ECG Evolution of STEMI

STEMI Diagnostic Criteria (J-point elevation in ≥2 contiguous leads)

UA/NSTEMI ECG Findings

• New horizontal or downsloping ST depression ≥0.05 mV in ≥2 contiguous leads
• T-wave inversion ≥0.1 mV in ≥2 contiguous leads with prominent R wave or R/S >1
• ECG may also be entirely normal (does NOT exclude ACS)

Contiguous Lead Groups

• Anterior: V1-V6
• Inferior: II, III, aVF
• Lateral/Apical: I, aVL
• Right ventricular: V3R, V4R
• Posterior (inferolateral): V7-V9

Territory - Artery Correlations

False-Positive ST Elevation (STEMI Mimics - EXAM CRITICAL)

• Early repolarization (benign)
• Left ventricular hypertrophy (LVH)
• Left bundle branch block (LBBB) - use Sgarbossa criteria
• Ventricular paced rhythm
• Brugada syndrome
• Acute pericarditis
• Myocarditis
• Subarachnoid hemorrhage
• Hyperkalemia
• Stress cardiomyopathy (Takotsubo)
• Cholecystitis (RCA territory)

False-Negative (Can Miss ACS)

• Prior MI with Q waves + persistent ST elevation
• LBBB
• Ventricular paced rhythm
• The initial ECG is nondiagnostic in ~50% of ED patients ultimately diagnosed with STEMI
• ~20% of patients ultimately diagnosed with AMI have nondiagnostic initial ECGs

• Rosen's Emergency Medicine, p. 411-413; Frameworks for Internal Medicine, p. 33

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5. BIOMARKERS

Troponin (I or T) - Gold Standard

• Cardiac-specific (cTnI, cTnT)
• Rise begins: 3-6 hours after onset
• Peak: ~24 hours
• Duration of elevation: 7-10 days (TnI), up to 14 days (TnT)
• High-sensitivity troponin (hsTn): Can detect elevation within 1-3 hours; enables 0h/1h or 0h/2h protocols
• UA = no rise in troponin; NSTEMI = troponin rises

Other Biomarkers

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6. RISK STRATIFICATION SCORES

HEART Score (Designed specifically for ED use)

• 0-3: Low risk - safe for discharge + outpatient workup
• 4-6: Moderate risk - observation + additional testing
• 7-10: High risk - early invasive strategy

TIMI Risk Score (for UA/NSTEMI - 7 variables, 1 point each)

1. Age ≥65
2. ≥3 CAD risk factors
3. Prior coronary stenosis ≥50%
4. ST deviation on presenting ECG
5. ≥2 anginal events in prior 24h
6. Prior aspirin use in past 7 days
7. Elevated serum cardiac markers

GRACE Score

• Based on: age, HR, SBP, creatinine, Killip class, cardiac arrest at admission, elevated markers, ST deviation
• Predicts in-hospital and 6-month mortality
• Originally derived for inpatients; the HEART score is preferred in the ED

EDACS (Emergency Department Assessment of Chest Pain Score)

• Another validated ED-specific tool
• Incorporates: age, sex, known CAD, diaphoresis, radiation, exertional pain
• Rosen's Emergency Medicine, p. 570-577

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7. WORKUP IN THE ED

• Echocardiography - wall motion abnormalities (regional hypokinesis/akinesis) in ischemia
• Coronary CT Angiography (CCTA) - useful in low-to-intermediate risk patients; radiation 2-5 mSv; requires heart rate control; high NPV for CAD

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8. MANAGEMENT

Initial Universal Management (ALL ACS)

Antiplatelet Therapy (Dual Antiplatelet - DAPT)

Anticoagulation

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9. STEMI-SPECIFIC MANAGEMENT

Time Targets (Exam Critical)

• Door-to-ECG: ≤10 minutes
• Door-to-balloon (primary PCI): ≤90 minutes
• Door-to-needle (fibrinolysis): ≤30 minutes
• If PCI-capable center, primary PCI is preferred over fibrinolysis

Reperfusion Strategy Decision

STEMI confirmed
    ↓
PCI-capable center available within 120 min of first medical contact?
    YES → Primary PCI
    NO  → Fibrinolysis (if no contraindications) within 30 min

Fibrinolytic Therapy

• Any prior intracranial hemorrhage (ever)
• Ischemic stroke within 3 months
• Known structural cerebrovascular lesion (AVM)
• Known intracranial malignancy
• Active bleeding (not menses)
• Significant closed-head trauma within 3 months
• Suspected aortic dissection

• SBP >180 or DBP >110 at presentation
• History of chronic severe hypertension
• Ischemic stroke >3 months ago
• Current anticoagulation use
• Traumatic/prolonged (>10 min) CPR
• Major surgery within 3 weeks
• Recent internal bleeding (2-4 weeks)
• Pregnancy
• Active peptic ulcer disease
• Non-compressible vascular punctures

RV Infarction (inferior STEMI with RV involvement)

• ECG: ST elevation in V3R-V4R
• Management:
  • IV fluids (preload-dependent RV)
  • AVOID nitrates (will drop preload and cause profound hypotension)
  • AVOID diuretics
  • AVOID morphine (preload reduction)
  • Consider atropine or pacing for bradycardia
  • Early reperfusion is critical

Killip Classification (LV failure severity post-MI)

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10. NSTEMI/UA MANAGEMENT

Initial Management

• DAPT (aspirin + P2Y12 inhibitor)
• Anticoagulation (enoxaparin or UFH preferred; fondaparinux if high bleeding risk)
• Beta-blocker (oral, unless contraindicated)
• Statin (high-intensity: atorvastatin 80 mg or rosuvastatin 40 mg)
• Consider IV nitroglycerin for ongoing ischemia

Invasive vs. Conservative Strategy

• TIMI ≥3 or GRACE >140
• Refractory angina despite medical therapy
• Hemodynamic instability
• Elevated troponin
• New ST changes
• Signs of heart failure
• High HEART score (7-10)

• Low TIMI score, low HEART score
• No high-risk features
• Patient preference

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11. COMPLICATIONS OF ACS

Dysrhythmias (most common complication, 72-100% of AMI)

Mechanical Complications (usually Day 3-7)

Cardiogenic Shock

• Most serious complication; mortality ~50-80%
• Defined: SBP <90 mmHg + signs of hypoperfusion
• Management: early PCI/revascularization, intra-aortic balloon pump (IABP), vasopressors (norepinephrine preferred), consider LVAD/Impella

Pericarditis (Dressler Syndrome)

• Post-MI pericarditis (2-10 weeks post-MI)
• Symptoms: fever, pleuritic chest pain, pericardial rub
• Treatment: ASA + colchicine; avoid NSAIDs/steroids in early post-MI period

Left Ventricular Aneurysm

• Persistent ST elevation weeks after STEMI
• Associated with VT, mural thrombus (anticoagulate), HF

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12. SPECIAL POPULATIONS & SCENARIOS

Elderly Patients

• Higher morbidity/mortality; independent risk factor for death
• Higher rate of atypical presentation
• ~50% of STEMI patients ≥85 years present with heart failure on admission vs 1.7% in those <65
• No absolute age cutoff for revascularization per AHA guidelines
• Early invasive strategy still preferred, but consider quality of life and goals of care

Cocaine/Amphetamine-Induced ACS

• Mechanism: vasospasm + accelerated atherosclerosis + in-situ thrombosis
• Cocaine inhibits reuptake of catecholamines → vasoconstriction
• Management:
  • Benzodiazepines (first-line for cocaine chest pain)
  • AVOID beta-blockers (unopposed alpha stimulation → paradoxical vasoconstriction)
  • NTG and calcium channel blockers (verapamil, diltiazem)
  • Aspirin
  • PCI if STEMI criteria met

LBBB and ACS (Sgarbossa Criteria)

• Concordant ST elevation ≥1 mm in a lead with a positive QRS (+5 points)
• Concordant ST depression ≥1 mm in V1-V3 (+3 points)
• Discordant ST elevation ≥5 mm (+2 points)

Type 2 MI

• Not from plaque rupture; from supply/demand mismatch
• Causes: tachyarrhythmias, anemia, hypotension, sepsis, respiratory failure
• Treat underlying cause; anticoagulation/PCI may not be indicated

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13. NITRATE CONTRAINDICATIONS (Exam Must-Know)

1. SBP <90 mmHg (hypotension)
2. Inferior STEMI with suspected/confirmed right ventricular infarction
3. Use of PDE-5 inhibitors within:
   • 24 hours (sildenafil, vardenafil)
   • 48 hours (tadalafil)
   • Results in severe refractory hypotension

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14. BETA-BLOCKER USE IN ACS

• Signs of acute decompensated heart failure or cardiogenic shock
• High degree AV block (without pacemaker)
• Active bronchospasm/severe COPD
• Bradycardia (HR <60)
• SBP <100 mmHg

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15. QUICK SUMMARY TABLE

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16. HIGH-YIELD PEARLS FOR EMD EXAM

1. ECG within 10 min - every suspected ACS patient, no exceptions
2. Single normal ECG does NOT exclude ACS - repeat serially
3. Aspirin 162-325 mg chewed - non-enteric coated, give ASAP
4. NTG is contraindicated in RV infarction - this is a classic exam vignette
5. Avoid beta-blockers in cocaine-induced chest pain
6. HEART score is the validated ED-specific risk tool (not TIMI/GRACE)
7. Morphine caution - may increase adverse events in some ACS patients; not withheld universally but use judiciously
8. Fibrinolysis absolute contraindication: any prior intracranial hemorrhage - no exceptions
9. AIVR post-STEMI = reperfusion arrhythmia - do NOT treat
10. Mechanical complications (VSD, papillary rupture, free wall rupture) peak at Day 3-7
11. Door-to-balloon ≤90 min / Door-to-needle ≤30 min
12. RV infarction triad: hypotension + elevated JVP + clear lungs → give fluids, not diuretics

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