Non ST-Elevation Myocardial Infarction (NSTEMI)

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Background

  • 33% with confirmed MI have no chest pain on presentation (especially older, female, DM, CHF)
  • 5% of NSTEMI will develop Cardiogenic Shock (60% mortality)
  • Age >65 with 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

Risk of ACS

Clinical factors that increase likelihood of ACS/AMI:[1][2]

Clinical factors that decrease likelihood of ACS/AMI:[3]

  • Pleuritic chest pain
  • Positional chest pain
  • Sharp, stabbing chest pain
  • Chest pain reproducible with palpation

Male and female patients typical present with similar symptoms[4]

Differential Diagnosis

Chest pain

Critical

Emergent

Nonemergent

Evaluation

  • Non-STEMI ECG + positive troponin
  • CK-MB and myoglobin are not helpful[5]

Management

  • 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
    • Administer sublingual NTG every 5 min # 3 for continuing ischemic pain and then assess need for IV NTG (AHA ACA Level I)
    • No shown decrease in MACE
    • Use cautiously in inferior MI or if on sildenafil
      • Decreases preload
    • B-block to avoid reflex tachycardia
  3. Analgesia
    • Morphine (AHA ACA Level IIb)
    • Do not use NSAIDs other than ASA (AHA ACA Level III: Harm)
  4. B-Blockers
    • No IV BB in ED (AHA ACA Level III: Harm), PO within 24 H
    • Goal HR is 50-60
    • Contraindicated if HR<50 or SBP<90, acute CHF, low flow state, or PR>240ms
    • Decreases progression from UA to MI by 13%
    • Decrease inotropic and chronotropic response to catechols
    • Use diltiazem if cannot use beta-blocker (nifedipine clearly harmful)
  5. ACE inhibitor
    • start short-acting (captopril) within 24hr of admission
    • Reduces RR of 30 day mortality by 7%
    • Those with recent MI (especially anterior) and LV dysfunction benefit most
  6. Transfusion
    • Transfuse to keep hemoglobin>10
  7. Magnesium
    • Reduces pain and theoretically can decrease HR, SBP and O2 demand
    • Correct hypomagnesiemia

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 (eg Anaphylaxis)
  2. Clopidogrel (see drug link for specific age, indication related dosages)
    • Give in addition to ASA
    • Mortality benefit with NSTEMI
    • Main risk and contraindication is bleeding
    • CURE trial: Decrease in cardiovascular death, MI or stroke by 9.3-11.5%
  3. GPIIb/IIIa Inhibitors
    • Eptifibatide, abciximab, tirofiban
    • Benefit only for patients undergoing PCI
      • Administer at time of PCI, not in the ED

Antithombotics

  1. Give heparin or enoxaparin along with ASA (Class 1A evidence)
  2. Enoxaparin
    • AHA recommends for moderate & high risk Unstable angina/NSTEMI unless CABG within 24hr
    • 1mg/kg subq BID
    • Safer than UFH
      • ESSENCE showed 20% decrease in death, MI or urgent revasc with LMWH
    • Adjust for CrCl<30ml and extremes of weight
    • No need to monitor labs
  3. Unfractionated Heparin
    • Consider if patient 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 with or with out symptoms 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 within previous 6 mo
  9. Prior CABG

Prognosis

NSTEMI TIMI Score[7]

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

See Also

External Links

References

  1. ↑ Body R, Carley S, Wibberley C, et al. The value of symptoms and signs in the emergent diagnosis of acute coronary syndromes. Resuscitation. 2010;81(3):281–286. PMID: 20036454
  2. ↑ Panju AA, Hemmelgarn BR, Guyatt GH, et al. The rational clinical examination. Is this patient having a myocardial infarction? JAMA. 1998;280(14):1256–1263. PMID: 9786377
  3. ↑ Swap CJ, Nagurney JT. Value and limitations of chest pain history in the evaluation of patients with suspected acute coronary syndromes. JAMA. 2005;294(20):2623–2629. PMID: 16304077
  4. ↑ Gimenez MR, et al. Sex-specific chest pain characteristics in the early diagnosis of acute myocardial infarction. JAMA Intern Med. 2014; 174(2):241-249.
  5. ↑ AHA ACA - NSTEMI ACS Guidelines 2014View Online
  6. ↑ CAPRIE Steering Committee.. A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee. Lancet. 1996 Nov 16;348(9038):1329-39.
  7. ↑ 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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