Non-ST-elevation myocardial infarction

Background

1. 33% w/ confirmed MI have no CP on presentation (esp older, female, DM, CHF)
2. 5% of NSTEMI will develop Cardiogenic Shock (60% mortality)
3. Age >65 w/ MI and anemia had 33% reduction in 30 day mort if transfused to keep HCT >30
4. Association between quantity of troponin and risk of death

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

Antiplatelet

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

Antithombotics

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

Thrombolytics

1. Only useful for STEMI

Angiography

1. 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

See Also

• Acute Coronary Syndrome (Main)
• Cocaine Chest Pain

Source

• Tintinalli
• EM Practice Guidelines
• UpToDate