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Myocardial Ishcemia and Infarction

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Title: Myocardial Ishcemia and Infarction


1
Myocardial Ishcemia and Infarction
  • Chapter 8 St Segment Elevation Ischemia and Q
    Wave Infarct Patterns

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

3
Transmural Ischemia
  • Acute Phase
  • St segment elevation
  • Sometimes tall T waves in certain leads
  • Acute phase may last hours to days

4
Transmural Ischemia
  • Evolving phase
  • T wave inversion in the leads where the
    previously showed ST segment elevation

5
Transmural Ischemia
  • Location
  • Anterior
  • Leads V1 - V6, I and aVl
  • Inferior
  • Leads II, III and aVf

6
Anterior MI
7
Inferior MI
8
Recipocity
Compare the anterior leads (V1 - V6, I and aVl)to
the inferior leads (II, III and aVf)
9
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
10
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

11
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

12
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
13
Tall T waves in V2-V5
Abnormal Q waves in V1 and V2
14
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.

15
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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21
Inferior Infarctions
FYI
  • Abnormal Q waves in leads II, III, and aVF

22
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23
Other
FYI
  • Posterior Infarctions
  • Right Ventricular Infarctions
  • Ventricular Aneurysm
  • Multiple Infarctions
  • Silent MI
  • MI with Bundle Branch Block

24
Myocardial Ischemia and Infarction
  • Chapter 9 St Segment Depression Ischemia and
    non-Q Wave Infarct Patterns

25
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

26
Subendocardial Ischemia
27
Subendocardial Ischemia
  • Transient ST segment depression
  • ST segment depression often occurs with angina,
    which generally returns to baseline when the
    angina subsides

28
Subendocardial Ischemia
  • Exercise

29
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.

30
Subendocardial Ischemia
  • False-Positive
  • ST depression without disease
  • False-Negative
  • Disease without ST depression
  • Silent Myocardial ischemia

31
Subendocardial Infarction
  • Persistent ST depression

32
Subendo-cardial Infarction
T wave inversion
33
Non-Specific ST-T changes
FYI
  • Subtle changes
  • slight flattening of T wave
  • minimal T wave inversion

34
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

35
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