Initial assessment and triage

Initial Assessment - The First 10 Minutes

• ABCs & Vitals: Immediate stabilization, focused history, and physical exam.
• Initial Setup: IV access (2 large-bore), cardiac monitor, pulse oximetry.
• Oxygen: Only if O₂ saturation < 90% or in respiratory distress.
• Medications (Concurrent):
  • Aspirin: 325 mg (chewed) immediately.
  • Nitroglycerin (sublingual): For active pain. ⚠️ Caution with hypotension, bradycardia, or recent PDE-5 inhibitor use.
  • Morphine: For pain refractory to nitroglycerin.

⭐ A 12-lead ECG must be obtained and interpreted within 10 minutes of arrival. If initial ECG is non-diagnostic but suspicion is high, consider posterior leads (V7-V9).

ECG Interpretation - Reading the Lines

• Primary Goal: Identify ST-elevation MI (STEMI) for emergent reperfusion.
• STEMI Criteria: New ST elevation at the J-point in ≥2 contiguous leads.
  • ≥1 mm in most leads.
  • In leads V2-V3: ≥2 mm in men ≥40y, ≥2.5 mm in men <40y, or ≥1.5 mm in women.
• NSTEMI/Ischemia: New horizontal or downsloping ST depression ≥0.5 mm or T-wave inversion ≥1 mm.
• Pathologic Q-waves: Indicate prior MI; >0.04s wide & >25% of R-wave height.

⭐ A new or presumed new Left Bundle Branch Block (LBBB) in a patient with ischemic chest pain is considered a STEMI equivalent.

Cardiac Biomarkers - Chemical Footprints

• Troponins (cTnI, cTnT): The gold standard for MI diagnosis due to high sensitivity and specificity.
  • Rise: 2-4 hrs
  • Peak: 24-48 hrs
  • Duration: 7-10 days
  • 📌 Troponin lasts up to Ten days.
• Creatine Kinase-MB (CK-MB):
  • Rise: 4-6 hrs
  • Peak: 12-24 hrs
  • Baseline: 48-72 hrs
  • Useful for detecting reinfarction.

⭐ High-sensitivity troponin (hs-cTn) can rule out MI faster (e.g., in a 0/1-hour algorithm).

Immediate Triage - The MONA-BASH Protocol

📌 MONA-BASH is a classic mnemonic, though treatment order varies. Aspirin first!

• Aspirin: 162-325 mg chewed immediately to inhibit platelet aggregation. Reduces mortality.
• Oxygen: Supplemental O₂ only if saturation is <90% or in respiratory distress.
• Nitroglycerin: Sublingual/IV. Vasodilator; reduces preload and pain.
  • Contraindicated in hypotension (SBP <90 mmHg), recent PDE-5 inhibitor use, or right ventricular infarction.
• Morphine: IV for refractory chest pain despite nitrates. Also reduces preload.
• Beta-Blockers: e.g., Metoprolol. Reduces O₂ demand and arrhythmias. Start within 24h if no signs of heart failure/shock.
• ACE Inhibitors: Start within 24h, especially in patients with anterior MI, heart failure, or EF <40%.
• Statin: High-intensity (e.g., Atorvastatin 80 mg) initiated ASAP, regardless of baseline cholesterol.
• Heparin (UFH or LMWH): Anticoagulation to prevent further thrombus formation.

⭐ Beta-blockers are one of the few initial therapies (along with Aspirin and reperfusion) that have a proven mortality benefit in acute MI.

• Initial management includes ABCs, IV access, cardiac monitoring, and a 12-lead ECG within 10 minutes.
• Administer chewable aspirin (162-325 mg) immediately to all patients without contraindications.
• Supplemental O₂ is only for hypoxemia (SaO₂ <90%) or respiratory distress.
• Nitroglycerin for chest pain is contraindicated in right ventricular infarction, severe aortic stenosis, or recent PDE-5 inhibitor use.
• Morphine is a second-line analgesic for pain refractory to nitrates.