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Acute Coronary Syndrome (ACS)

mLpenguin

• 2 min read
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Acute Coronary Syndrome (ACS)
Photo by Sharan Pagadala / Unsplash

What is ACS?

Acute Coronary Syndrome is an umbrella term for conditions caused by acute myocardial ischemia due to coronary artery occlusion. The three main entities are:

  1. ST-Elevation Myocardial Infarction (STEMI) – complete coronary occlusion with transmural infarction.
  2. Non-ST-Elevation Myocardial Infarction (NSTEMI) – partial occlusion with myocardial injury (positive troponin).
  3. Unstable Angina (UA) – ischemia without detectable myocardial injury (negative troponin).

Pathophysiology

Most ACS cases are due to:

  • Atherosclerotic plaque rupture → exposure of lipid core → platelet aggregation → thrombus formation → reduced coronary blood flow.
  • Less common: coronary vasospasm (Prinzmetal angina), emboli, spontaneous coronary artery dissection.

The degree and duration of obstruction determine whether you get STEMI, NSTEMI, or UA.

Classic & Atypical Presentations

Classic

  • Central, crushing chest pain or pressure (“elephant on the chest”)
  • Radiates to jaw, neck, shoulder, or left arm
  • Associated diaphoresis, dyspnea, nausea/vomiting, anxiety

Atypical (common in elderly, women, diabetics)

  • Epigastric discomfort
  • Dyspnea without chest pain
  • Weakness, confusion, syncope
  • Palpitations
Always think ACS in: unexplained shortness of breath, syncope, or new confusion in high-risk patients.

Initial ED Priorities (First 10 Minutes)

Think MONA BASH + ECG

  1. Airway, breathing, circulation (ABCs) - stabilize first.
  2. Cardiac monitor and IV access x2.
  3. 12-lead ECG - should be obtained within 10 minutes of arrival.
  4. Focused history & physical - risk factors, onset, character of pain.
  5. Labs - cardiac troponin, CBC, BMP, coagulation panel, type & screen.

ECG Interpretation in ACS

Your goal: Identify STEMI immediately

  • STEMI criteria: New ST elevation in ≥2 contiguous leads
    • ≥1 mm (0.1 mV) in all leads except V2–V3
    • V2–V3: ≥1.5 mm in women, ≥2 mm in men ≥40, ≥2.5 mm in men <40
  • Look for reciprocal ST depression (often confirms STEMI).
  • NSTEMI/UA: May show ST depression, T-wave inversion, or be normal.
A normal ECG does not rule out ACS - especially early.

Risk Stratification Tools

In the ED, these help guide disposition and urgency:

  • TIMI Score (UA/NSTEMI risk of death/MI)
    • Risk at 14 days of: all-cause mortality, new or recurrent MI, or severe recurrent ischemia requiring urgent revascularization.
    • Age ≥65
    • ≥3 CAD risk factors
      • Hypertension, hypercholesterolemia, diabetes, family history of CAD, or current smoker
    • Known CAD (Setnosis ≥50%)
    • ASA use in the past 7 days
    • Severe angina (≥2 episodes in 24 hrs)
    • EKG ST changes ≥0.5mm
    • Positive cardiac marker
  • GRACE Score (mortality prediction)
    • Age
    • Heart rate/pulse
    • Systolic BP
    • Creatine
    • Cardiac arrest at admission
    • ST Segmenet deviation on EKG
    • Abnormal cardiac enzymes
    • Killip class
      • No CHF
      • Rales and/or JVD
      • Pulmonary edema
      • Cardiogenic shock
Unstable vitals, dynamic ECG changes, or rising troponin = high risk.

Management

General Measures (All suspected ACS)

MONA BASH

  • Morphine for pain refractory to nitrates
  • Oxygen if SpO₂ <90%
  • Nitroglycerin sublingual if not hypotensive and no RV infarct
  • Aspirin 325 mg chewed (unless contraindicated)

  • Beta-blockers (within 24 hrs if no contraindications)
  • Antiplatelet therapy: P2Y₁₂ inhibitor (clopidogrel, ticagrelor)
  • Statins
  • Heparin - Anticoagulation: unfractionated heparin or LMWH

Specific

STEMI:

    • PCI within 90 minutes door-to-balloon (preferred)
    • If PCI unavailable: fibrinolysis within 30 min door-to-needle (if no contraindications)

NSTEMI/UA:

    • Early invasive strategy if high risk
    • Medical stabilization and cardiology consult

Special Situations

  • Right ventricular infarct (often with inferior MI) → Avoid nitrates (can drop preload dangerously).
  • Posterior MI → Look for ST depression in V1–V3, confirm with posterior leads.
  • Elderly & Diabetic patients → Often present without chest pain.

Key Takeaways

Time is myocardium - recognize and act fast.

  • Get the ECG within 10 minutes.
  • Treat suspected ACS before the labs confirm it.
  • Risk stratify and involve cardiology early.
  • Always consider ACS in high-risk patients with vague symptoms.