II. Advantages

  1. Ischemic EKG changes best acute MI evidence
    1. Applies if symptom onset within last 3 hours
  2. Normal/Nondiagnostic initial EKG predicts low risk

III. Disadvantages

  1. Poor sensitivity for Myocardial Infarction (40-50%)
    1. 3-10% of MI patients have initial normal EKG
    2. 25% of patients with missed MI had misread EKG

IV. Precautions

  1. The computer over-reads abnormal EKGs
  2. Compare with prior EKGs (Increases Test Specificity)!
  3. Obtain serial EKGs if initial EKG is non-diagnostic
    1. May repeat EKG every 15 min for 1-2 hours
  4. Consider Myocardial Ischemia if ST depression >0.5 mm

V. Images

  1. Acute ST Elevation Myocardial Infarction with delayed presentation (ST Elevation and Q Waves present)
    1. cv_STEMI_LatePresentation.jpg
  2. Acute ST Elevation Myocardial Infarction evolving from Hyperacute T Waves

VI. Findings: EKG Markers of underlying CAD

  1. Left Ventricular Hypertrophy
  2. ST Segment changes
  3. T Wave changes
  4. Diagnostic Q Waves in 2 contiguous leads
  5. Left Bundle Branch Block or other conduction changes

VII. Findings: General EKG Changes suggestive of Myocardial Ischemia

  1. Electrocardiogram may be completely normal
  2. ST Elevation or ST depression
    1. Over 1 mm ST changes that are transient with symptoms
    2. Summed ST deviation (sum of affected leads) >2.5 mm
      1. Holmvang (2003) J Am Coll Cardiol 41:905-15 [PubMed]
    3. ST Elevation criteria in leads V2-V3 varies by age and gender
      1. Men age <40 years old
        1. V2-V3 ST Elevation >2.5 mm
        2. Accounts for Early Repolarization in young men
      2. Men age >40 years old
        1. V2-V3 ST Elevation >2 mm
      3. Women
        1. V2-V3 ST Elevation >1.5 mm
  3. Deep symmetric T-wave inversion
    1. Occurs in multiple precordial leads
  4. Left main Coronary Artery stenosis marker
    1. ST Depression >1 mm in 8 or more leads (esp I, II, V4-6) AND ST Elevation in aVR, aVL or V1
      1. Suggests multi-vessel ischemia or left main obstruction
    2. aVR ST Segment Elevation > V1 ST Segment Elevation
      1. Gaitonde (2003) Am J Cardiol 92:846-8 [PubMed]
    3. Biphasic or deep T Wave Inversion in V2, V3 (Wellen's Syndrome)
      1. High risk for left anterior descending artery ischemia and Anterior Wall Myocardial Infarction
  5. Left Anterior Descending Artery Occlusion
    1. Hyperacute T Waves with J Point Depression (De Winter T Waves, seen in 2% of LAD lesions)
      1. J Point depression with upsloping ST Segment AND
      2. Tall, prominent, hyperacute precordial T Waves
        1. Hyperacute T Waves also seen in Hyperkalemia, STEMI without J Point depression

VIII. Findings: General EKG Changes suggestive of Acute Myocardial Infarction

  1. New left ventricular strain pattern
  2. New Left Bundle Branch Block
  3. Q Waves
    1. At least 0.04 sec wide and 1/3 height of R Wave
    2. Unless isolated in Lead III
  4. T Wave Inversion
    1. Significant unless isolated to Lead III or Lead V1
    2. T Wave must be at least 1 mm deep
    3. T Wave Inversion within 4 hours of reperfusion is a reassuring prognostic sign
  5. ST-T elevation (>1mm in limb or precordial leads)
    1. Must have >=2 concordant leads with changes
  6. ST depression in Lead V1, Lead V2 (Posterior MI)
  7. Hyperacute T Waves (over 50% of preceding R)
    1. Must have 2 or more leads with changes

IX. Findings: Septal MI Anatomic Distribution

  1. Electrocardiogram Changes
    1. Lead V1 to lead V2
  2. Distribution
    1. Left Coronary Artery: LAD-Septal Branch
  3. Complications
    1. Infranodal and Bundle Branch Block

X. Findings: Anterior MI Anatomic Distribution

  1. EKG Changes
    1. ST Elevation in lead V2 to lead V4
    2. ST depression in leads II, III, avF (variably present)
  2. Distribution
    1. Left Coronary Artery: LAD-Diagonal branch
  3. Complications
    1. Worse prognosis
    2. High risk of sudden death
    3. High risk of Congestive Heart Failure in first year
    4. Complete Heart Block

XI. Findings: Inferior MI Anatomic Distribution

  1. EKG Changes
    1. ST Elevation in leads II, III, aVF
    2. Q Waves in leads III, aVF
    3. ST depression and T Wave Inversion in lead aVL (reciprocal change)
  2. Distribution
    1. Right Coronary Artery: Posterior descending branch
  3. Complications
    1. Right Ventricular Infarction
      1. Inferior heart wall lies along the diaphragm
    2. Distended neck veins with clear lungs
    3. Systolic Blood Pressure drops with
      1. Morphine
      2. Nitroglycerin

XII. Findings: Lateral MI Anatomic Distribution

  1. EKG Changes
    1. ST Segment Elevation in leads V5, V6, I, aVL
      1. I and aVL are considered contiguous leads (high lateral wall)
      2. ST Elevation in both I and aVL is considered STEMI criteria for immediate reperfusion
    2. ST segment Depression in leads V1, V2, V3, III, aVF (reciprocal change)
  2. Distribution
    1. Left Coronary Artery: Circumflex branch
  3. Complications
    1. Left Ventricular Dysfunction
    2. AV nodal block

XIII. Findings: Right Ventricular Infarction Anatomic Distribution

  1. Standard EKG Changes (similar to anterior MI EKG when rotated 180 degrees)
    1. ST Elevation in leads I and aVF, and lead III more than II
    2. ST depression in leads I, aVL (reciprocal to posterior changes)
  2. Right sided EKG
    1. Right Lead Positioning
      1. Right lead V1 at left of Sternum (standard V2 position)
      2. Right lead V2 at right of Sternum (standard V1 position)
      3. Right lead V6 at right posterolateral chest
    2. Alternative: V4R
      1. Simply move V4 lead to the right chest (5th intercostal space, mid-clavicular line)
    3. Findings
      1. ST Elevation >1mm in V4R
      2. Q Waves are normal in right-sided leads and are not indicative of Myocardial Infarction history
  3. Distribution
    1. Right Coronary Artery: Proximal branches
  4. Complications
    1. Severe and refractory Hypotension in response to nitrates
      1. Treated with fluid bolus and nitrates are contraindicated

XIV. Findings: Posterior Infarction Anatomic Distribution

  1. Standard EKG Changes
    1. ST depression in leads V1 to V4
      1. Differentiate from reciprocal changes in inferior-lateral MI
      2. Contrast with right sided infarct with ST Elevation in V1 to V4
    2. Tall R Wave (>0.04 seconds) in leads V1 and V2
    3. Interpret V2 by rotating the axis 180 degrees (or apply posterior leads)
      1. Tall R Wave rotates to a Q Waves
      2. ST depression rotates to ST Elevation
      3. T Wave rotates to T Wave Inversion
  2. Posterior EKG Changes
    1. Leads V8 and V9 (placed on left back, below left Scapula) demonstrate ST Elevation
  3. Distribution
    1. Distal Right Coronary Artery: Posterior descending
    2. Left Coronary Artery: Circumflex
  4. Complications
    1. Left Ventricular Dysfunction

Images: Related links to external sites (from Bing)

Related Studies

Ontology: Septal infarction by electrocardiogram (C0232319)

Concepts Laboratory or Test Result (T034)
SnomedCT 1077002
English Septal infarction by electrocardiogram (finding), Septal infarction by EKG, Septal infarction by EKG (finding), Septal infarction by electrocardiogram
Spanish signos electrocardiográficos de infarto septal (hallazgo), signos electrocardiográficos de infarto septal

Ontology: Anteroseptal infarction on electrocardiogram (C0232320)

Concepts Finding (T033)
SnomedCT 164868007, 22111008, 142028001
English ECG: antero-septal infarct., Electrocardiogram: anteroseptal infarction, Electrocardiogram: anteroseptal infarction (finding), Anteroseptal infarction on electrocardiogram, Anteroseptal infarction on electrocardiogram (finding), ECG: anteroseptal infarction, ECG: antero-septal infarct, Anteroseptal infarction by EKG, ECG: anteroseptal infarction (finding), Anteroseptal infarction by EKG (finding)
Spanish infarto anteroseptal en el electrocardiograma (hallazgo), infarto anteroseptal en el electrocardiograma, electrocardiograma: infarto anteroseptal, electrocardiograma: infarto anteroseptal (hallazgo), signos electrocardiográficos de infarto anteroseptal (hallazgo), signos electrocardiográficos de infarto anteroseptal, ECG: infarto anteroseptal

Ontology: Inferior myocardial infarction on electrocardiogram (C0232323)

Concepts Laboratory or Test Result (T034)
SnomedCT 7326005
English Inferior infarction by EKG (finding), Inferior myocardial infarction on electrocardiogram, Inferior myocardial infarction on electrocardiogram (finding), Inferior infarction by EKG
Spanish infarto de miocardio inferior en el electrocardiograma, signos electrocardiográficos de infarto inferior (hallazgo), signos electrocardiográficos de infarto inferior

Ontology: Lateral infarction on electrocardiogram (C0232325)

Concepts Finding (T033)
SnomedCT 164871004, 87064008, 142031000
English Electrocardiogram: lateral infarction, ECG: lateral infarction, Lateral infarction on electrocardiogram (finding), Electrocardiogram: lateral infarction (finding), Lateral infarction on electrocardiogram, Lateral infarction by EKG (finding), ECG: lateral infarction (finding), Lateral infarction by EKG
Spanish electrocardiograma: infarto lateral, infarto lateral en el electrocardiograma (hallazgo), infarto lateral en el electrocardiograma, electrocardiograma: infarto lateral (hallazgo), signos electrocardiográficos de infarto lateral, signos electrocardiográficos de infarto lateral (hallazgo), ECG: infarto lateral

Ontology: ECG myocardial ischemia (C0474715)

Definition (NCI) An electrocardiographic finding of ST and T wave changes consistent with impaired myocardial perfusion.
Concepts Finding (T033)
SnomedCT 164861001, 164864009, 57740008, 142021007, 142024004
English ECG: myocardial ischaemia, ECG: myocardial ischemia, ECG myocardial ischemia (finding), ECG: myocardial ischemia NOS (finding), EKG findings of ischemia (finding), Electrocardiogram: myocardial ischaemia, Electrocardiogram: myocardial ischemia (finding), Electrocardiogram: myocardial ischemia, ECG: myocardial ischaemia NOS, ECG: myocardial ischemia NOS, Myocardial Ischemia by ECG Finding, ECG myocardial ischemia, ECG: myocardial ischaemia NOS (finding), Electrocardiogram finding of ischemia (finding), Electrocardiogram finding of ischemia, ECG: myocardial ischaemia (finding), Electrocardiogram: myocardial ischaemia NOS, Electrocardiogram: myocardial ischemia NOS, Electrocardiogram finding of ischaemia, Electrocardiogram: myocardial ischemia NOS (finding), EKG findings of ischemia, EKG findings of ischaemia, Myocardial Ischemia by EKG Finding, ECG myocardial ischaemia
Spanish hallazgos electrocardiográficos de isquemia (hallazgo), hallazgos electrocardiográficos de isquemia, hallazgo electrocardiográfico de isquemia (hallazgo), ECG: myocardial ischaemia NOS, electrocardiograma: isquemia miocárdica, SAI (hallazgo), electrocardiograma: isquemia miocárdica, SAI, ECG: myocardial ischemia NOS, ECG: isquemia miocárdica, SAI, hallazgo electrocardiográfico de isquemia, ECG: isquemia miocárdica, electrocardiograma: isquemia miocárdica (hallazgo), electrocardiograma: isquemia miocárdica

Ontology: Electrocardiogram: anterior ischemia (C1960086)

Concepts Finding (T033)
SnomedCT 426434006
English Electrocardiogram: anterior ischemia (finding), ECG: anterior ischaemia, Electrocardiogram: anterior ischaemia, Electrocardiogram: anterior ischemia
Spanish electrocardiograma: isquemia anterior (hallazgo), ECG: isquemia anterior, electrocardiograma: isquemia anterior

Ontology: Electrocardiogram: inferior ischemia (C1960087)

Concepts Finding (T033)
SnomedCT 425419005
English Electrocardiogram: inferior ischemia, Electrocardiogram: inferior ischemia (finding), Electrocardiogram: inferior ischaemia, ECG: inferior ischaemia
Spanish electrocardiograma: isquemia inferior, ECG: isquemia inferior, electrocardiograma: isquemia inferior (hallazgo)

Ontology: Electrocardiogram: lateral ischemia (C1960088)

Concepts Finding (T033)
SnomedCT 425623009
English Electrocardiogram: lateral ischemia (finding), Electrocardiogram: lateral ischemia, ECG: lateral ischaemia, Electrocardiogram: lateral ischaemia
Spanish electrocardiograma: isquemia lateral, ECG: isquemia lateral, electrocardiograma: isquemia lateral (hallazgo)