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

Diagnosis

  1. Angina is considered unstable with 1 or more:
    1. Occurs for 1st time
    2. Occurs at rest
    3. Accelerating frequency or severity

Treatment

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. Rec dose is 160-325mg 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 (sup in preventing post-proc MI)
    2. Used over ticlopidine b/c faster onset & less s/e
    3. Mortality benefit with NSTEMI
    4. Main risk and contraindication is bleeding
    5. CURE - Decr in CV death, MI or stroke by 9.3-11.5%
  3. GPIIb/IIIa(-) = Eptifibatide, abciximab
    1. Pts undergoing PCI benefit most
      1. If no PCI need high risk features (+trop, ischemia despite ASA, lovenox)
    2. Incr ICH not seen w/ use

Antithombotics

  1. Class1A evidence to anticoagulate w/ heparin or lovenox along w/ ASA
  2. LMWH: Enoxaparin
    1. 1mg/kg sc BID
    2. Safer than UFH
      1. ESSENCE showed 20% decr in death, MI or urgent revasc w/ LMWH
    3. AHA recommends for mod & high risk UA/NSTEMI unless CABG w/in 24hr
    4. Adjust for CrCl<30ml and extremes of weight
    5. No need to monitor labs
  3. Hirudin is approved only for pts w/ HIT
  4. Unfractionated Heparin
    1. Bolus 60-70u/kg (max 5000) followed by infusion of 12-15u/kg/hr (max 1000/hr), goal ptt 45-75s

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

Source

Tintinalli

EM Practice

UpToDate

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