NSTEMI diagnosis and management

NSTEMI Pathophysiology - The Unstable Plaque

• Core Mechanism: Rupture of an atherosclerotic plaque triggers platelet aggregation and thrombus formation.

  • The key distinction is a partially occlusive thrombus, which limits but doesn't eliminate blood flow.
  • This leads to subendocardial ischemia and necrosis, hence the elevated cardiac biomarkers (Troponins).

• Spectrum of ACS:

  • Unstable Angina: Ischemia without necrosis (negative biomarkers).
  • STEMI: A fully occlusive thrombus causing transmural ischemia.

⭐ Plaque rupture most commonly occurs at the shoulder region of the fibrous cap, an area weakened by inflammatory cells.

NSTEMI Diagnosis - The Clinical Picture

• Clinical Presentation: Substernal chest pain >20 min, often with dyspnea, diaphoresis, or nausea. Atypical symptoms (fatigue, epigastric pain) common in women, diabetics, and the elderly.
• ECG Findings: Key ischemic changes include ST-segment depression (≥0.5 mm) or dynamic T-wave inversions (≥1 mm). A normal ECG does not rule out NSTEMI.
• Cardiac Biomarkers: High-sensitivity cardiac troponin (hs-cTn) is the gold standard.
  • Serial measurements (e.g., at 0 and 1-3 hours) are crucial.
  • Look for a characteristic rise and/or fall pattern.

⭐ A normal initial ECG occurs in up to 20% of NSTEMI cases; repeat ECGs are essential if clinical suspicion remains high.

Risk Stratification - Scoring the Danger

Guides timing of intervention (invasive vs. conservative).

• TIMI Score: Predicts 30-day risk of death, MI, or revascularization.

  • Age ≥65
  • Markers (positive cardiac)
  • EKG (ST deviation ≥0.5 mm)
  • Risk factors for CAD (≥3: HTN, HLD, DM, smoking, family hx)
  • Ischemia (≥2 anginal events in 24h)
  • CAD (known, stenosis ≥50%)
  • Aspirin use in past 7 days
  • 📌 Mnemonic: AMERICA

• GRACE Score: More complex, but more accurate for in-hospital & long-term mortality.

⭐ The GRACE score is superior to the TIMI score in predicting mortality, especially in higher-risk patients.

NSTEMI Management - The Action Plan

• Initial Medical Therapy:
  • DAPT: Aspirin + P2Y12 inhibitor (e.g., Ticagrelor).
  • Anticoagulation: Unfractionated or LMW Heparin.
  • Beta-blockers: Metoprolol (cardioselective).
  • Statin: High-intensity (e.g., Atorvastatin 80 mg).
  • Nitrates for angina relief.

⭐ In patients with NSTEMI and cardiogenic shock or refractory angina, emergent (<2h) coronary angiography is recommended.

High-Yield Points - ⚡ Biggest Takeaways

• NSTEMI is an ACS with positive cardiac biomarkers (troponin) but no ST-segment elevation on EKG.
• It is differentiated from Unstable Angina by the presence of elevated troponins, indicating myocardial necrosis.
• Initial management includes dual antiplatelet therapy (DAPT)-Aspirin plus a P2Y12 inhibitor-and anticoagulation.
• Risk stratification with TIMI or GRACE scores is crucial to guide therapy toward an early invasive strategy.
• Beta-blockers reduce myocardial oxygen demand; nitrates provide symptom relief.