ST-segment elevation myocardial infarction: Difference between revisions

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*[[Acute Coronary Syndrome (Main)]]
*[[Acute Coronary Syndrome (Main)]]
*[[ST Segment Elevation (DDX)]]
*[[ST Segment Elevation (DDX)]]
*[[EBQ:Sgarbossa Criteria Study]]
*[[Sgarbossa's criteria]]
*http://emcrit.org/podcasts/left-bundle-branch-block/
*http://emcrit.org/podcasts/left-bundle-branch-block/


Revision as of 03:41, 28 November 2014

Background

  • RV infarction accompanies ~25% of inferior STEMIs
    • Hemodynamically significant only 10% of the time
  • Posterior infarction is rarely isolated (~3-8% of all AMIs)
    • Usually will see changes in V6 OR II, III, aVF

Anatomical Correlation

ACS Anatomical Correlation Chart

Ischemic Changes Location Coronary Artery
STE V1-V3, TWI

Q waves in V1-V3 over time

Septal Septal branch
STE V2-V4 Anterior LAD
STE I, aVL, V5, V6

STD inf leads

Lateral Circumflex
STE I, aVL, V2-6 Anterolateral LAD + circumflex = Left main or 2 critical lesions
STE II, III, aVF

STD in aVL (most common lead to see reciprocal change)

Inferior RCA

STE V1 (only lead looking at RV)
STE III > II (III more R facing)
STE V1 > V2, STE V1 + STD V2

Right ventricle RCA

STD in V1, V2, V3;
R>S in V1
Tall R waves in V1-V3 (Q waves on back of heart) w/ upright TWs

Posterior aka Inferolateral RCA (90%), LCA (10%)
STE avR>V1

Doesn't apply in SVT

Anterolateral Left Main

Prehospital

Patients with a STEMI on the prehospital ECG but resolution of ST elevations on arrival require activation of the cath team or transfer for primary catheterization even though there has been resolution of the ST-elevations. There is a high likelihood of a significant coronary occlusion.[1]

Diagnosis

Use the J-point for measurement in 2 contiguous leads:[2]

  1. Men ≥ 40yo:
    1. 2mm in V2-V3 and 1mm in all other leads
  2. Men ≤ 40yo:
    1. 2.5mm in V2-V3 and 1mm in all other leads
  3. Women:
    1. 1.5mm in V2-V3 and 1mm in all other leads

New LBBB

  • New Left Bundle Branch Block is no longer a STEMI criteria for activation of the cath lab as of 2013[3]
  • Sick patients with a new LBBB should be discussed with a cardiologist for possible PCI

Sgarbossa's Criteria in LBBB

Original Criteria

Sgarbossa's Original Criteria

≥3 points = 98% probability of STEMI[4]

  • ST elevation ≥1 mm in a lead with upward QRS complex (concordant) - 5 points
  • ST depression ≥1 mm in lead V1, V2, or V3 - 3 points
  • ST elevation ≥5 mm in a lead with downward QRS complex (discordant) - 2 points

Smith's modification[5]

Smith's Modified Sgarbossa 3rd Rule
  • Changes the 3rd rule of original Sgarbossa's Criteria to be ST depression OR elevation discordant with the QRS complex and with a magnitude of at least 25% of the QRS
    • Increases Sn from 52% → 91% at the expense of reducing Sp from 98% → 90%

DDx

  1. Myocardial ischemia or infarction
  2. Noninfarction, transmural ischemia (Prinzmetal's angina pattern or acute takotsubo cardiomyopathy)
  3. Post-MI (ventricular aneurysm pattern)
  4. Previous MI with recurrent ischemia in same area
  5. Pericarditis
  6. Early repolarization
  7. LVH or LBBB (only V1-V2 or V3)
  8. Myocarditis (may look like myocardial infarction or pericarditis)
  9. Brugada Syndrome
  10. Myocardial tumor
  11. Myocardial trauma
  12. Hyperkalemia (only leads V1 and V2)
  13. Hypothermia (J wave/Osborn wave)

Treatment

Adjunctive

  1. O2
    1. esp for SpO2 <90%
  2. ASA 162-325mg chewable or 600mg PR
  3. NTG
  4. Morphine
  5. Beta-Blocker:
    1. PO within 24 hours
    2. IV beta-blocker is reasonable for patients who are hypertensive in the absence of:
      1. Heart failure
      2. Low cardiac output state
      3. Cardiogenic shock risk factors
        1. Age > 70yr, sys BP < 120, HR > 110 or <60,
      4. Conduction block (PR interval > 0.24s, 2nd or 3rd block
      5. Active asthma

Antiplatelets

Clopidogrel

  • Loading dose of 600mg if PCI anticipated (otherwise give 300mg)
  • No loading dose if >75yr receiving fibrinolytics

Ticagrelor

  • May significantly reduce mortality as compared to clopidogrel[6]
  • 180 mg loading dose, followed by 90 mg BID
  • Ticagrelor offers no added benefit in STEMI when given pre-hospital vs. in-hospital (ambulance vs. cath lab)[7]

GPIIB/IIIa Inhibitors

  • Abciximab, Eptifibatide
  • Defer to cardiologist
  • Given right before PCI depending on specific institutional protocols

Anticoagulation

  1. Heparin (UFH)
    1. Bolus 60U/kg (max: 4000U) followed by 12U/kg/h (max: 1000U/h)
    2. Titrate to PTT 1.5-2.5 x control
  2. LMWH
    1. <75yo with serum Cr < 2.5 mg/dL (men) or < 2.0 mg/dL (women):
      1. 30mg IV bolus followed by 1mg/kg SC q12h
    2. ≥ 75yo
      1. 0.75mg/kg SC q12h
    3. CrCl < 30 mL/min
      1. 1mg/kg SC qd
  3. Fondaparinux
    1. Cr < 3.0 mg/dL:
      1. 2.5mg IV bolus then 2.5mg SC qd started 24hr after bolus
    2. Monitor anti-Xa levels
  4. Bivalirudin
    1. 0.75mg/kg IV bolus followed by 1.75 mg/kg/h
    2. CrCl < 30 mL/min
      1. 0.75mg/kg IV bolus followed by 1.0 mg/kg/h

Definitive

  1. Fibrinolytics
    1. Goal: Give within 30min
    2. If receive fibrinolytics also give anticoagulants for minimum of 48hr
    3. Fibrinolytic tx w/in 3hr resulted in >30 lives saved per 1000 pts
    4. 0.5-1% of pts suffer ICH
  2. PCI
    1. Goal: Give within 90min (acceptable delay may be up to 120min)

Fibrinolysis

Indications

  1. <12hr from onset of CP AND:
    1. ST elevation of ≥1mm in 2 contiguous limb or precordial leads OR new LBBB

Contraindications

  1. Absolute contraindications
    1. Any prior ICH
    2. Known structural cerebral vascular lesion (AVM)
    3. Known intracranial neoplasm
    4. Ischemic stroke w/in 3 mo
    5. Active internal bleeding (excluding menses)
    6. Suspected aortic dissection or pericarditis
  2. Relative contraindications
    1. Severe uncontrolled BP (>180/100)
    2. History of chronic severe poorly controlled HTN
    3. History of prior ischemic stroke >3 mo
    4. Known intracranial pathology not covered in absolute contraindications
    5. Current use of anticoagulants with known INR >2–3
    6. Known bleeding diathesis
    7. Recent trauma (past 2 wk)
    8. Prolonged CPR (>10 min)
    9. Major surgery (<3 wk)
    10. Noncompressible vascular punctures (e.g. IJ, subclavian)
    11. Recent internal bleeding (within 2–4 wk)
    12. Pts treated previously with streptokinase should not receive streptokinase a 2nd time
    13. Pregnancy
    14. Active peptic ulcer disease
    15. Other medical conditions likely to increase risk of bleeding (diabetic retinopathy, etc)

Dosing (Alteplase)

  • >67kg pt:
    • Infuse 15mg IV over 1-2min; then 50mg over 30min; then 35mg over next 60min (i.e. 100mg over 1.5hr)
  • ≤67kg pt:
    • Infuse 15mg IV over 1-2min; then 0.75 mg/kg (max 50mg) over 30 min; then 0.5 mg/kg over 60min (max 35 mg)

Dosing (Tenecteplase-TNKase)

  • Reconstitute 50 mg vial in 10 mL sterile water (5 mg/mL)
  • < 60 kg = 30 mg IV push over 5 seconds
  • 60-69 kg = 35 mg IV push over 5 seconds
  • 70-79 kg = 40 mg IV push over 5 seconds
  • 80-89 kg = 45 mg IV push over 5 seconds
  • > 90 kg = 50 mg IV push over 5 seconds

Rescue PCI

  • Failed reperfusion: consider if repeat EKG 90 minutes after infusion fails to show reduction of elevated ST segments by 50%
  • Recurrent significant ST elevation following successful lysis
  • Persistent hemodynamically unstable arrythmias, persistent ischemic symptoms, or worsened cardiogenic shock

See Also

External Links

Source

  • Electrocardiography in Emergency Medicine. ACEP Textbook
  1. ↑ Ownbey M, Suffoletto B, Firsch A, et al. Prevalence and interventional outcomes of patients with resolution of ST-segment elevation between prehospital and in-hospital ECG. Prehosp Emerg Care. 2014. Apr-Jun;18(2):174-9
  2. ↑ Thygesen, K., Alpert, J. S., Jaffe, A. S., Simoons, M. L., Chaitman, B. R., White, H. D., et al. (2012). Third Universal Definition of Myocardial Infarction. JACC, 60(16), 1581–1598. doi:10.1016/j.jacc.2012.08.001
  3. ↑ Am Heart J 2013;166:409-13
  4. ↑ Sgarbossa E. et al.. "Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators". NEJM. 1996. 334(8):481-7
  5. ↑ Smith, S. et al. Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule. 60(6). 766-776
  6. ↑ Wallentin et Al. Ticagrelor versus Clopidogrel in Patients with Acute Coronary Syndromes. N Engl J Med 2009; 361:1045-1057.
  7. ↑ Montalescot G et al. Prehospital ticagrelor in ST-segment elevation myocardial infarction. N Engl J Med 2014 Sep 1.
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