What are the clinical features and management of acute coronary syndrome (ACS)?

Clinical Features and Management of Acute Coronary Syndrome

Acute coronary syndrome (ACS) is characterized by a sudden reduction in coronary blood flow resulting from plaque rupture or erosion with varying degrees of thrombosis and distal embolization, requiring immediate risk stratification and management to reduce mortality and morbidity. 1

Clinical Presentation

Symptoms

• Typical presentation (80% of cases): Prolonged (>20 min) anginal chest pain/discomfort at rest described as pressure, tightness, or burning 1
• Atypical presentations (20% of cases) are more common in:
  • Elderly (>75 years)
  • Women
  • Diabetic patients
  • Young adults (25-40 years) 1

Atypical presentations include:

• Dyspnea (most common equivalent)
• Epigastric pain
• Pain radiating to left arm, jaw, neck, back, or shoulder
• Recent onset indigestion
• Increasing dyspnea 1

Features less characteristic of ACS:

• Pleuritic pain (sharp pain provoked by respiration)
• Pain localized by fingertip
• Pain reproduced with movement/palpation
• Brief episodes lasting seconds
• Pain maximal at onset 1

Physical Examination

Physical examination is often normal but serves to:

• Exclude non-cardiac causes of chest pain
• Exclude non-ischemic cardiac disorders (pericarditis, valvular disease)
• Identify potential precipitating factors
• Detect signs of hemodynamic instability or left ventricular dysfunction 1

Diagnostic Evaluation

Immediate Assessment (within 10 minutes)

1. 12-lead ECG: Crucial for classifying ACS into two categories 1, 2:

   • ST-elevation ACS (STE-ACS): Persistent ST-segment elevation >20 min
   • Non-ST-elevation ACS (NSTE-ACS): Transient ST-segment elevation, ST-segment depression, T-wave inversion, flat T waves, pseudo-normalization of T waves, or normal ECG

2. High-sensitivity cardiac troponin: Obtain at 0h and 1h (or 0h and 3h if high-sensitivity assay not available) 2

   • Elevated troponin with clinical context confirms myocardial infarction
   • Serial measurements help distinguish between NSTEMI and unstable angina

Additional Testing

• Complete blood count
• Renal function tests
• Echocardiography to evaluate left ventricular function and rule out other causes 2

Risk Stratification

TIMI Risk Score for NSTE-ACS 1

Score	Risk of adverse outcomes
0-1	4.7%
2	8.3%
3	13.2%
4	19.9%
5	26.2%
6-7	40.9%

GRACE Score 2

• Score >140: High risk
• Score 109-140: Intermediate risk

Management

Initial Management

1. Oxygen therapy: Only if oxygen saturation <90% or respiratory distress 2
2. Pain relief: Morphine IV/SC for persistent severe chest pain 2

Antiplatelet Therapy

1. Aspirin: 150-300mg loading dose, then 75-100mg daily maintenance indefinitely 2
2. P2Y12 inhibitor for 12 months:
   • Ticagrelor (180mg loading, 90mg twice daily): First choice for moderate to high-risk patients 2
   • Prasugrel (60mg loading, 10mg daily): For patients proceeding to PCI
     • Contraindicated in patients with history of stroke/TIA
     • Generally not recommended for patients ≥75 years or <60kg 2, 3
   • Clopidogrel (300-600mg loading, 75mg daily): For patients who cannot receive ticagrelor or prasugrel 2

Anticoagulation

Choose one of the following:

• Unfractionated heparin
• Enoxaparin
• Fondaparinux
• Bivalirudin 2

Invasive Management

1. Immediate invasive strategy (<2 hours):

   • Hemodynamic instability
   • Cardiogenic shock
   • Life-threatening arrhythmias
   • Ongoing ischemia 2

2. Early invasive strategy (<24 hours):

   • GRACE score >140
   • Dynamic ECG changes
   • Elevated troponin 2

3. Revascularization strategy:

   • Single-vessel disease: PCI of culprit lesion
   • Left main or triple-vessel disease: CABG generally recommended
   • Double-vessel disease: Either PCI or CABG based on clinical factors 2

Additional Therapies

1. High-intensity statin therapy: Start as early as possible 2
2. Beta-blockers: Within 24 hours if no contraindications 2
3. ACE inhibitors: For patients with LV dysfunction, heart failure, hypertension, or diabetes 2
4. Aldosterone antagonists: For post-MI patients with LVEF ≤40% and either diabetes or heart failure 2

Common Pitfalls and Caveats

1. Diagnostic challenges:

   • Atypical presentations are common in women, elderly, and diabetic patients
   • Normal ECG does not exclude ACS (up to 41% of NSTE-ACS have no ECG changes) 4

2. Treatment considerations:

   • Avoid prasugrel in patients with history of stroke/TIA (contraindicated) 3
   • Discontinue prasugrel at least 7 days before surgery when possible 3
   • Be cautious with antiplatelet therapy in patients <60kg due to increased bleeding risk 3

3. Follow-up:

   • Schedule follow-up 1-2 weeks for high-risk patients
   • Continue dual antiplatelet therapy for 12 months after PCI 2
   • Emphasize risk factor modification and cardiac rehabilitation 2

By promptly recognizing ACS symptoms, performing appropriate diagnostic tests, and implementing evidence-based therapies, clinicians can significantly improve outcomes for patients with this potentially life-threatening condition.