Acute Coronary Syndrome: Characteristics, Diagnosis, and Treatment

Acute coronary syndrome (ACS) is a medical emergency that involves a sudden reduction in blood flow to the heart muscle due to a blockage of a coronary artery. It includes acute myocardial infarction (MI) and unstable angina (UA).

1. Acute Myocardial Infarction (MI)

1.1 Characteristics of a Typical Angina Attack:

• Typical Angina:
  • Sudden onset: Begins abruptly, often without a clear reason.
  • Location: Pain behind the breastbone or radiating to the left side.
  • Radiation: Can radiate to the neck, left shoulder, arm, and the fourth and fifth fingers.
  • Quality: Squeezing, crushing, heavy.
  • Duration: Lasts for several minutes to several hours.
  • Pain relief: Rest and nitroglycerin often provide little relief.
• Characteristics of Unstable Angina:
  • New onset angina that is severe within 48 hours.
  • Angina that occurs at rest.
  • Progressive angina: Chest pain becomes more severe, longer-lasting, and more frequent.

1.2 Other Clinical Manifestations:

• Systolic murmur:
  • Pansystolic murmur: Due to MI-induced rupture of the papillary muscle of the mitral valve, leading to mitral regurgitation.
  • Systolic + diastolic murmur: Due to ventricular septal rupture.
• Killip classification: Evaluates the severity of heart failure:
  • I: No signs of heart failure.
  • II: Mild to moderate signs of heart failure (S3 gallop, rales < 1/2 of the lungs, distended jugular veins).
  • III: Pulmonary edema.
  • IV: Cardiogenic shock.

1.3 Diagnosis of ST-segment Elevation MI on ECG:

• Diagnostic Criteria:
  • ST elevation ≥ 1 mm in at least two consecutive leads: D2, D3, aVF, V1-V6, D1, aVL.
  • Presence of left bundle branch block/ischemia.
  • Presence of Q waves in at least two consecutive leads with a width > 30 ms and a depth > 1 mm or QS morphology.
• Consider inferior wall MI: Perform additional V3R, V4R (ST elevation only needs to be ≥ 0.5 mm for women or men > 40 years old).
• Consider lateral wall MI: Perform additional V7-V9 (only needs to be ≥ 0.5 mm).
• Repeat ECG: After 90 minutes of thrombolytic therapy and immediately after percutaneous coronary intervention in patients with ST elevation.

1.4 Localization of Coronary Artery Disease:

• Anterior wall: ST elevation in V1-V4 (anterior septum) or from V1-V6 (extensive septum).
• Inferior wall: Elevation in DII, DIII, aVF.
• Lateral wall: DI, aVL, V5-V6.

1.5 Coronary artery blockage is considered successfully reperfused when:

• ST elevation decreases by at least 50% compared to before intervention or thrombolytic therapy.

1.6 Laboratory Tests:

• Troponin:
  • Changes within 1-4 hours after MI, peaks at 24-48 hours, and remains elevated for 7-14 days.
  • Difficult to detect re-infarction.
  • Significant concentration changes when:
    • Minimum change > 20% of the initial value if initially above the normal range.
    • Minimum increase > 50% of the threshold value if initially below the threshold.
• CK/CKMB: Increased 3-12 hours after infarction, peaks within 24 hours, and returns to normal after 48-72 hours.
• Echocardiography: Shows regional wall motion abnormalities: hypokinesis, akinesis, dyskinesis to ventricular aneurysm.

2. Unstable Angina (UA)

• Characteristics: Chest pain similar to MI, but no clear signs of myocardial damage on ECG.
• Diagnosis: Based on clinical factors, ECG, cardiac enzymes, and echocardiography.

3. Differentiation from other pathologies:

• Acute aortic syndrome: Severe chest pain radiating to the back, disproportionate between symptoms and ECG, cardiac enzymes, blood pressure difference between the two arms, mediastinal widening, aortic dissection on echocardiography.
• Pulmonary infarction: Chest pain, dyspnea, hemoptysis but no pulmonary edema, blood gas analysis showing decreased PaO2 and PaCO2, ECG: S1Q3, CT scan confirms.
• Pericarditis: Pain is sharp, worse with position change, increased when lying supine, ECG: ST elevation concordant in the anterior leads and no mirror image.
• Acute myocarditis: Difficult to differentiate, history of previous infection, echocardiography: diffuse hypokinesis.

4. Treatment of Acute Coronary Syndrome:

4.1 Coronary Artery Reperfusion:

• Indications:
  • All patients with new-onset ST elevation or left bundle branch block, within 12 hours of onset.
  • ACS presenting after 12 hours but still with ongoing myocardial necrosis/ischemia, percutaneous coronary intervention is preferred.
  • Consider reperfusion for stabilized patients presenting 12-24 hours after onset.
  • Patients presenting > 24 hours after onset who are stabilized are not routinely intervened.

4.2 Pain Management:

• Morphine sulfate IV is the mainstay at 2-5 mg, repeated after 5-10 minutes.
• Sublingual nitroglycerin 0,4 mg, beware of hypotension.

4.3 Thrombolytic Therapy:

• Fibrin-specific agents are preferred (tenecteplase is preferred due to reduced risk and ease of use as it only requires a single injection).

4.4 Anticoagulation and Antiplatelet Therapy:

• Used immediately and after thrombolytic therapy.
• Anticoagulation:
  • Heparin if coronary intervention is planned: maintain aPTT at 50-70 seconds or 1.5-2 times control.
  • Enoxaparin is preferred if intervention is not planned.
• Antiplatelet therapy: Aspirin loading dose 162-325 mg + clopidogrel loading dose 300 mg < 75 years old or 75 mg > 75 years old.

4.5 Duration of Dual Antiplatelet Therapy:

Minimum of 1 year if no bleeding complications.

4.6 If patients are at high risk of stent thrombosis, poor flow after intervention:

Add enoxaparin for 1-5 days (maximum 8 days).

4.7 In patients with atrial fibrillation or left atrial thrombus:

Oral anticoagulation (vitamin K antagonist or NOAC).

4.8 If patients have heart failure or left ventricular dysfunction after MI:

• Use beta-blockers long-term if no contraindications.
• Use ACEIs within the first 24 hours after reperfusion if the patient also has diabetes or anterior wall MI, use long-term.
• Use angiotensin II receptor blockers (ARBs) instead of ACEIs if the patient is intolerant.
• Use aldosterone antagonists if heart failure EF < 40% or diabetes if no renal impairment or hyperkalemia.

4.9 Differences in treatment of STEMI vs NSTEMI:

• Thrombolytic therapy is not used in NSTEMI.

4.10 Management of ABCDE for patients with acute coronary syndrome:

• A5: Antiplatelet, anticoagulation, ACE, angiotensinogen blocker, aldosterone receptor blocker.
• B2: Blood pressure, beta-blocker.
• C2: Cigarette cessation, cholesterol.
• D2: Diabetes, diet.
• E2: Exercise, EF.

4.11 Absolute contraindications to thrombolytic therapy:

• History of stroke.
• Cerebral infarction within 6 months.
• Presence of central nervous system lesions, cerebral vascular malformations.
• Severe head injury within 3 weeks.
• Gastrointestinal bleeding within 1 month.
• Coagulation disorders.
• Aortic dissection.

5. Silent MI:

• Presentation with fatigue, reduced exercise tolerance, without clear angina.
• Occurs in elderly patients, post-surgery, elderly, dementia, stroke sequelae, diabetes.

6. Precautions during Emergency Coronary Intervention:

• Mandatory use of one anticoagulant: bivalirudin, heparin, enoxaparin.
• Do not use fondaparinux for early intervention.

7. TIMI (STEMI) Score:

• Evaluates the risk of mortality in patients with STEMI.

8. CADILLAC Score:

• Evaluates the risk of mortality during emergency percutaneous coronary intervention.
• Less effective before intervention because it requires using left ventricular function parameters.

Note: This article is for general informational purposes only and does not substitute for professional medical advice. If you have any symptoms suggestive of acute coronary syndrome, seek immediate medical attention for diagnosis and treatment.