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

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

• Acute Coronary Syndrome (Main)
• Cocaine Chest Pain

Source

Tintinalli

EM Practice

UpToDate