ACS Notes

Acute Coronary Syndromes (ACS) – Study Notes

Core Goals in ACS

• Rapid ECG: Obtain within 10 minutes.
• Identify candidates for reperfusion therapy (PCI or thrombolytics).
• Medical therapy: Initiate anti-ischemic and antithrombotic treatment early.
• Risk assessment tools: e.g., HEART score for risk stratification.

ACS Spectrum (Traditional Definition)

1. STEMI:

   • ST elevation in contiguous leads + troponin elevation.
   • Suggests full-thickness infarct.
   • Requires emergent reperfusion.

2. NSTEMI:

   • Symptoms of ischemia + troponin elevation.
   • No ST elevation; may show ST depression or T-wave inversions.
   • Often partial-thickness involvement.

3. Unstable Angina:

   • Ischemic symptoms but no troponin elevation.
   • New, worsening, or rest angina.

OMI Concept (Occlusion MI)

• Traditional STEMI/NSTEMI classification misses ~40% who need reperfusion.
• OMI approach emphasizes identifying occlusion requiring reperfusion even if criteria for STEMI are not met.
• Consider:
  • STEMI equivalents.
  • Clinical picture + ischemic ECG changes + biomarkers.
  • Avoid rigid reliance on definitions.

2021 Chest Pain Guideline Updates

• Use “chest discomfort” instead of “chest pain.”
• Avoid the term “atypical chest pain.”
  • Use cardiac / possible cardiac / non-cardiac or simply low-risk chest pain.
• Symptom variability in women: more likely to present with SOB, nausea, fatigue.
• Relief with GI cocktail does not rule out ACS.
• Bias awareness: elderly, women, and minorities often underdiagnosed.

ECG Localization of MI

• Inferior (II, III, aVF): RCA.
• Anterior/Septal (V1–V4): LAD (“Widowmaker”).
• Lateral (I, aVL, V5–V6): LCx.
• Posterior MI: Tall R in V1–V2 + ST depression (looks like “NSTEMI”). Confirm with posterior leads (V7–V9).

STEMI criteria:

• New ST elevation at J point, in ≥2 contiguous leads.
• ≥1 mm elevation, except in V2–V3:
  • Men ≥40: ≥2 mm.
  • Men <40: ≥2.5 mm.
  • Women: ≥1.5 mm.

STEMI Equivalents

• Posterior MI (ST depression V1–V4 + tall R).
• De Winter T waves (tall, symmetric T with upsloping ST depression).
• LBBB / RV-paced rhythm with modified Sgarbossa criteria.
• Diffuse ST depression with STE in aVR (suggests LAD occlusion).

Medical Management

• Aspirin: Mortality benefit (NNT ~42).
• Dual antiplatelet therapy: Aspirin + P2Y12 inhibitor (clopidogrel, ticagrelor).
• Heparin: Bolus + infusion; procedural benefit for PCI.
• Nitroglycerin: Useful (esp. with pulmonary edema/HTN) unless hypotension, RV infarct, or PDE-5 inhibitors.
• Avoid routine oxygen unless hypoxic (can worsen outcomes).
• Avoid routine morphine: Delays antiplatelet absorption; possible harm.
• Beta-blockers: Avoid in acute/unstable phase (risk cardiogenic shock). Start later when stable.
• Statins: Start within 24 hrs (not emergent ED intervention).

Troponins

• Rise 3–6 hrs, peak 12–24 hrs, normalize in ~7 days.
• Causes beyond MI: sepsis, CHF, renal failure, PE, myocarditis.
• Type 1 NSTEMI: Primary plaque rupture/ischemia.
• Type 2 NSTEMI: Demand ischemia (e.g., sepsis, anemia).
• High-sensitivity troponin preferred (guidelines).

Reperfusion Targets

• Door-to-balloon (PCI): ≤90 min.
• Transfer to PCI center: ≤120 min.
• Door-to-needle (thrombolytics): ≤30 min.
• Thrombolytics: Use if PCI not available within timeframe, large myocardium at risk, and no contraindications.

Risk Stratification

• HEART score ≤3: Low risk → no urgent follow-up needed (safe up to 30 days).
• Intermediate risk: Consider CCTA or stress testing; shared decision-making.
• High risk / Ongoing ischemia / Instability: Admit and evaluate for PCI.

 The Takeaway:
The shift is from rigid STEMI/NSTEMI labels to OMI recognition, focusing on who needs reperfusion rather than just EKG definitions.