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. ACS = STEMI, NSTEMI, UA
  2. Angina is considered unstable with 1 or more:
    1. Occurs for 1st time
    2. Occurs at rest
    3. Accelerating frequency or severity
  3. ECG is normal in 8% of all confirmed MI's
  4. Intensity of Rx should be based on likelihood that sx are due to acute coronary thombosis

TIMI RISK STRATIFICATION SCORE

  1. 1 point for each
    1. Age ≥65 years
    2. Presence of at least three risk factors for CHD
    3. Prior coronary stenosis of ≥50 percent
    4. Presence of ST segment deviation on admission ECG
    5. At least two anginal episodes in prior 24 hours
    6. Elevated serum cardiac biomarkers
    7. Use of aspirin in prior seven days
  2. Likelihood of mortality, new or recurrent MI, or require revascularization at 14 days
    1. Score of 0/1 - 4.7 percent
    2. Score of 2 - 8.3 percent
    3. Score of 3 - 13.2 percent
    4. Score of 4 - 19.9 percent
    5. Score of 5 - 26.2 percent
    6. Score of 6/7 - 40.9 percent

Treatment

  1. Anti-ischemia
    1. Oxygen
      1. ACC recs O2 for sats <90% (evidence indeterminant)
    2. Nitrates
      1. No mortality benefit
      2. Dilates coronary arts, decr preload, slight decr afterload
      3. Use of viagra within 24hr can lead to profound and prolonged vasodilation (and death)
      4. B-block to avoid reflex tachycardia
    3. B-Blockers
      1. Goal HR is 50-60
      2. Contraindicated if HR<50 or SBP<90, acute CHF or PR>240ms
      3. (Decreases progression from UA to MI by 13%
      4. Decr inotropic and chronotropic response to catechols
      5. use dilt or verap if can't use b-block (nifedipine clearly harmful)
      6. No IV BB in ED, PO within 24 H
    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. may use if pain after 3 doses of NTG
      2. Reduces pain and theoretically can decr HR and SBP and O2 demand
      3. Use associated with higher mortality in MI pts (and cause of higher mortality in CHF exacerbation pts)
  2. 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 (plavix 300mg po then 75qd)
      1. In addition to ASA
      2. Used over ticlopidine b/c faster onset & less s/e
      3. Mortality benifit with NSTEMI
      4. Main risk and contraind is bleeding
      5. CURE trial showed decr in CV death, MI or stroke by 9.3-11.5%
    3. GPIIb/IIIa(-) = Eptifibatide (Integrillin)
      1. High-risk pts benefit most
        1. PURSUIT trial found 30 day death or MI decr from 15.7% to 14.2%
      2. Incr ICH not seen w/ use
      3. Benefit if early PCI is planned; ? to no benefit if PCI not planned
      4. Reserved (if no pci) for positive trop or isch/ecg changes despite ASA, lovenox, b-block etc
  3. Antithombotics
    1. Class1A evidence to anticoagulate w/ heparin or lovenox along w/ asa
    2. Unfractionated Heparin
      1. Bolus 60-70u/kg (max 5000) followed by infusion of 12-15u/kg/hr (max 1000/hr), goal ptt 45-75s
    3. LMWH: Enoxaparin (lovenox)
      1. 1mg/kg sc BID
      2. Safer (ESSENCE showed 20% decr in death, MI or urgent revasc w/ LMWH vs UFH)
      3. AHA recomends 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
    4. Hirudin is approved only for pts w/ HIT
  4. Thrombolytics
    1. Only useful for STEMI
  5. Angiography indicated if:
    1. Hemodynamic instability or cardiogenic shock
    2. Severe left ventricular dysfunction or heart failure
    3. Recurrent or persistent rest angina despite intensive medical therapy
    4. New or worsening mitral regurgitation or new ventricular septal defect
    5. Sustained ventricular arrhythmias
  6. Early (within 24hr) referral for angiography if:
    1. TIMI risk score greater than 2
    2. New or presumably new ST segment depression
    3. Elevated cardiac enzymes
    4. Prior PCI within six months or prior CABG
    5. Recurrent angina or ischemia at rest or with low level activity despite intensive antiischemic therapy
    6. LVEF <40 percent

See Also

Cards: Cocaine CP

Source

EM Practice

UpToDate

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