Myocardial Ishcemia and Infarction

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Myocardial Ishcemia and Infarction

• Chapter 8 St Segment Elevation Ischemia and Q
  Wave Infarct Patterns

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Terminology

1. Ischemia
2. Angina Pectoris
3. Necrosis
4. Myocardial Infarction
5. Epicardium
6. Subendocardium
7. TransmuraL
8. three major coronary arteries

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Transmural Ischemia

• Acute Phase
• St segment elevation
• Sometimes tall T waves in certain leads
• Acute phase may last hours to days

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Transmural Ischemia

• Evolving phase
• T wave inversion in the leads where the
  previously showed ST segment elevation

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Transmural Ischemia

• Location
• Anterior
• Leads V1 - V6, I and aVl
• Inferior
• Leads II, III and aVf

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Anterior MI
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Inferior MI
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Recipocity
Compare the anterior leads (V1 - V6, I and aVl)to
the inferior leads (II, III and aVf)
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Anterior MI Inferior MI
Early Phase ST elevation Tall T waves V1-V6, I and aVl ST elevation Tall T waves II, III and aVf
Early Phase ST Depression in II, III and aVf St Depression in V1-V6, I and aVl
Evolving Phase Inverted T waves in V1-V6, I and aVl Inverted T waves in II, III and aVf
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ST Elevation

• The ST elevation seen with acute MI is called a
  Current of injury
• ST segment elevations are the earliest ECG signs
  of acute MI

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Q Waves

• Q waves are characteristic markers of infarction.
  (But not all transmural infarcts lead to Q
  waves.)
• New Q waves of an MI generally appear with the
  first day or two
• With an Anterior MI, these Q waves are seen in
  one of more of leads V1-V6, I and aVl
• With an Inferior MI, these Q waves are seen in
  one of more of leads II, III and aVf

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Normal Q Waves
Small Q waves Horizontal Axis
large Q waves
Small Q waves
Small Q waves Vertical Axis
Small Q waves Horizontal Axis
Small Q waves
Small Q waves Vertical Axis
Small Q waves Vertical Axis
Small Q waves
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Tall T waves in V2-V5
Abnormal Q waves in V1 and V2
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Normal and Abnormal Q Waves

• Normal
• Narrow (less than 0.04 sec), Low amplitude
• Abnormal if greater than 0.04 sec in leads I, II,
  III, aVf or leads V3 - V6.
• Wider Q waves in V1, V2, III, and aVf can be
  normal
• Not all Q waves are abnormal, Not all Q waves are
  the result of MI.

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Anterior Infarctions
FYI

• Anterior MI show loss of R wave progression in
  the chest leads
• Anterospetal Infarcts Loss of R waves in V1 and
  V2
• Strictly Anterior Infarcts Loss of R waves in
  V3 and V4
• Anterolateral or Anteroapical infarcts abnormal
  Q waves in V5 and V6

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Inferior Infarctions
FYI

• Abnormal Q waves in leads II, III, and aVF

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Other
FYI

• Posterior Infarctions
• Right Ventricular Infarctions
• Ventricular Aneurysm
• Multiple Infarctions
• Silent MI
• MI with Bundle Branch Block

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Myocardial Ischemia and Infarction

• Chapter 9 St Segment Depression Ischemia and
  non-Q Wave Infarct Patterns

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Subendocardial Ischemia

• Inner layer
• St Segment depression
• Anterior leads (I, aVl and V1-V6)
• Inferior leads (II, III, and aVf)
• May see ST segment elevation in aVr

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Subendocardial Ischemia
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Subendocardial Ischemia

• Transient ST segment depression
• ST segment depression often occurs with angina,
  which generally returns to baseline when the
  angina subsides

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Subendocardial Ischemia

• Exercise

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Subendocardial Ischemia

• ST segment depression criteria
• 1 mm or more
• horizontal or downward
• lasts 0.08 seconds
• depression of only the J point with rapid upward
  sloping are considered normal.

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Subendocardial Ischemia

• False-Positive
• ST depression without disease
• False-Negative
• Disease without ST depression
• Silent Myocardial ischemia

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Subendocardial Infarction

• Persistent ST depression

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Subendo-cardial Infarction
T wave inversion
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Non-Specific ST-T changes
FYI

• Subtle changes
• slight flattening of T wave
• minimal T wave inversion

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Prinzmetals Angina

• Transient ST segment elevation with angina
• No Q waves, no T wave inversion
• Angina may occur at rest or at night
• Coronary artery spasm

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