Cardiovascular Diseases: Myocardial Infarction Symptoms

Acute Coronary Syndrome (ACS)

• New-onset, crescendo, refractory, and post-MI/PCI types of ACS
• Associated symptoms:
  • Pallor, diaphoresis
  • N/V, dyspnea
  • Palpitations or light-headedness

Silent or Atypical MI

• ~20% of MIs are silent or atypical
• Atypical symptoms may include N/V, epigastric pain without chest pain
• More common in females, elderly, DM, and inferior ischemia

Physical Exam

• Signs of ischemia:
  • Diaphoresis
  • S4
  • Paradoxical S2
  • New MR murmur (papillary muscle dysfunction)
• Signs of HF:
  • HoTH
  • Cool extremities
  • Increased JVP
  • Lung crackles and S3
• Signs of other vascular disease:
  • Asymmetric BP
  • Carotid/femoral bruits
  • Decreased distal pulses

Approach to Triage

• ECG:
  • Within 10 minutes of presentation
  • After 15-30 minutes
  • Repeat 6-12 hours later if clinical changes occur
• Cardiac biomarkers:
  • cTn (preferred over CK-MB) at presentation and after 3-6 hours
  • Repeat 6-12 hours later if clinical or ECG changes occur
• If ECG and cTn remain normal and low likelihood of ACS, search for alternative causes
• If intermediate likelihood of ACS, rule out UA with stress test or CTA

Acute Anti-Ischemic/Analgesic/Anti-Thrombotic Measures

• NTG (SL or IV)
• β-blockers
• ± Oxygen
• ± Morphine
• Aspirin/Heparin

Likelihood of Acute Coronary Syndromes

• High likelihood:
  • Any of the following:
    • Chest/L arm pain
    • Reproducing pain
    • Documented angina
    • History of CAD (including MI)
• Intermediate likelihood:
  • NO high features BUT any of the following:
    • Chest/L arm pain
    • Male
    • >70 years old
    • DM
• Low likelihood:
  • NO high/intermediate features BUT may have:
    • Probable ischemic symptoms in absence of any intermediate features
    • Recent cocaine use

Definition of Acute Coronary Syndrome

• Spectrum of clinical presentations, including UA, NSTEMI, and STEMI
• UA/NSTEMI differentiated from STEMI by absence of STE
• Presentation of UA/NSTEMI similar, but in patients with NSTEMI, evidence of myocardial necrosis (cardiac biomarkers) is present

Extent of Ischemia

• Transmural ischemia:
  • Occurs with complete 100% flow obstruction (STEMI)
• Subendocardial ischemia:
  • Occurs with flow obstruction but some distal blood flow
  • Stable angina, unstable angina, and NSTEMI

Biomarkers

• Cardiac biomarkers:
  • Biomarkers spill into blood with cardiac injury
  • Most common marker used: troponin I/T
  • Increase 2-4 hours after MI
  • Stay elevated for weeks
  • CK-MB also used
  • Increase 4-6 hours after MI
  • Normalize within 2-3 days