Non-ST-elevation myocardial infarction

Background

  • 33% w/ confirmed MI have no CP on presentation (esp older, female, DM, CHF)
  • 5% of NSTEMI will develop Cardiogenic Shock (60% mortality)
  • Age >65 w/ MI and anemia had 33% reduction in 30 day mort if transfused to keep HCT >30
  • Association between quantity of troponin and risk of death
  • NSTEMI includes Type 2 -Type 5 biomarker elevations

Types of Myocardial Infarction

Type 1: Ischemic myocardial necrosis due to plaque rupture ( ACS)
Type 2: Ischemic myocardial necrosis due to supply-demand mismatch, e.g. coronary spasm, embolism, low or high blood pressures, anemia, or arrhythmias.
Type 3: sudden cardiac death (no cTr values)
Type 4: procedure related, post PCI or stent thrombosis ( cTr > 5X Decision Level).
Type 5 post CABG (cTr > 10X Decision Level).

Clinical Features

Differential Diagnosis

Chest pain

Critical

Emergent

Nonemergent

Treatment

  • Dual antiplatelet therapy is key
    • ASA + other agent (other agent depends on conservative vs interventional strategy)
      • Medical management vs cath determined by level of risk for future cardiovascular events

Anti-ischemia

  1. Oxygen
    • ACC recs O2 for sats <90% (evidence indeterminate)
  2. Nitrates
    • No mortality benefit
    • Use cautiously in inferior MI
      • Decreases preload
    • B-block to avoid reflex tachycardia
  3. B-Blockers
    • No IV BB in ED, PO w/in 24 H
    • Goal HR is 50-60
    • Contraindicated if HR<50 or SBP<90, acute CHF or PR>240ms
    • Decreases progression from UA to MI by 13%
    • Decrease inotropic and chronotropic response to catechols
    • Use dilt if can't use beta-blocker (nifedipine clearly harmful)
  4. ACE inhibitor
    • start short-acting (captopril) w/in 24hr of admission
    • Reduces RR of 30 day mort by 7%
    • Those w/ recent MI (esp ant) and LV dysfunction benefit most
  5. Transfusion
    • Transfuse to keep Hb>10
  6. Magnesium
    • Reduces pain and theoretically can decr HR, SBP and O2 demand
    • Correct hypomag

Antiplatelet

  1. Aspirin
    • Recommended dose is 325mg chewed
    • Reduces death from MI by 12.5-6.4%
    • Should be used in all ACS unless contraindicated
  2. Clopidogrel
    • Give in addition to ASA
      • 300mg
      • 600mg if going to PCI (superior in preventing post-proc MI)
    • Mortality benefit with NSTEMI
    • Main risk and contraindication is bleeding
    • CURE trial: Decr in CV death, MI or stroke by 9.3-11.5%
  3. GPIIb/IIIa Inhibitors
    • Eptifibatide, abciximab, tirofiban
    • Benefit only for pts undergoing PCI
      • Administer at time of PCI, not in the ED

Antithombotics

  1. Give heparin or enoxaparin along w/ ASA (Class 1A evidence)
  2. Enoxaparin
    • AHA recommends for moderate & high risk Unstable angina/NSTEMI unless CABG w/in 24hr
    • 1mg/kg subq BID
    • Safer than UFH
      • ESSENCE showed 20% decrease in death, MI or urgent revasc w/ LMWH
    • Adjust for CrCl<30ml and extremes of weight
    • No need to monitor labs
  3. Unfractionated Heparin
    • Consider if pt likely to undergo PCI/CABG within 24hr of admission
    • Bolus 60-70u/kg (max 5000) followed by infusion of 12-15u/kg/hr (max 1000/hr), goal ptt 45-75s
  4. Hirudin
    • Approved only for patients with HIT

Thrombolytics

Angiography

Indicated for:

  1. Recurrent angina/ischemia w/ or w/o sx of CHF
  2. Elevated troponins
  3. New or presumably new ST-segment depression
  4. High-risk findings on noninvasive stress testing
  5. Depressed LV function
  6. Hemodynamic instability
  7. Sustained V-tach
  8. PCI w/in previous 6 mo
  9. Prior CABG

Prognosis

NSTEMI TIMI Score[1]

Used to estimate percent risk of all-cause mortality, new/recurrent MI, or need for revascularization at 14 days
  • Age >65 yrs (1 point)
  • Three or more risk factors for coronary artery disease: (1 point)
    • family history of coronary artery disease
    • hypertension
    • hypercholesterolaemia
    • diabetes
    • current smoker
  • Use of aspirin in the past 7 days (1 point)
  • Significant coronary stenosis (stenosis >50%) (1 point)
  • Severe angina (e.g., >2 angina events in past 24 h or persisting discomfort) (1 point)
  • ST-segment deviation of ≥0.05 mV on first ECG (1 point)
  • Increased troponin and/or creatine kinase-MB blood tests (1 point)
TIMI Risks
points % risk of mortality, MI, or need for revascularization
0 5%
1 5%
2 8%
3 13%
4 20%
5 26%
6 41%

See Also

External Links

References

  1. ↑ Antman, Elliot et al. The TIMI Risk Score for Unstable Angina/Non–ST Elevation MI A Method for Prognostication and Therapeutic Decision Making. JAMA. 2000;284(7):835-842. doi:10.1001/jama.284.7.835. PDF
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