Myocardial Ishcemia and Infarction Chapter 8: St Segment Elevation Ischemia and Q Wave Infarct...
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Transcript of Myocardial Ishcemia and Infarction Chapter 8: St Segment Elevation Ischemia and Q Wave Infarct...
Myocardial Ishcemia and
InfarctionChapter 8: St Segment Elevation Ischemia
and Q Wave Infarct Patterns
Terminology1. Ischemia
2. Angina Pectoris
3. Necrosis
4. Myocardial Infarction
5. Epicardium
6. Subendocardium
7. TransmuraL
8. three major coronary arteries
Transmural Ischemia
Acute Phase
St segment elevation
Sometimes tall T waves in certain leads
Acute phase may last hours to days
Transmural Ischemia
Evolving phase
T wave inversion in the leads where the previously showed ST segment elevation
Transmural Ischemia
Location
Anterior
Leads V1 - V6, I and aVl
Inferior
Leads II, III and aVf
Anterior MI
Inferior MI
Recipocity
Compare the anterior leads (V1 -
V6, I and aVl)to the inferior
leads (II, III and aVf)
Anterior MI Inferior MI
Early Phase
ST elevationTall T waves
V1-V6, I and aVl
ST elevationTall T wavesII, III and aVf
ST Depression in II, III and aVf
St Depressionin V1-V6, I and
aVl
Evolving PhaseInverted T
waves in V1-V6, I and aVl
Inverted T waves in II, III
and aVf
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
Q WavesQ 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
Normal Q Waves
large Q waves
Small Q waves
Small Q waves
Small Q waves
Small Q wavesHorizontal Axis
Small Q wavesVertical Axis
Small Q wavesHorizontal Axis
Small Q wavesVertical Axis
Small Q wavesVertical Axis
Tall T waves in V2-V5
Abnormal Q waves in V1
and V2
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.
Anterior InfarctionsAnterior 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
FYI
Inferior Infarctions
Abnormal Q waves in leads II, III, and aVF
FYI
OtherPosterior Infarctions
Right Ventricular Infarctions
Ventricular Aneurysm
Multiple Infarctions
“Silent” MI
MI with Bundle Branch Block
FYI
Myocardial Ischemia and Infarction
Chapter 9: St Segment Depression Ischemia and non-Q Wave Infarct Patterns
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
Subendocardial Ischemia
Subendocardial IschemiaTransient ST segment depression
ST segment depression often occurs with angina, which generally returns to baseline when the angina subsides
Subendocardial Ischemia
Exercise
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.
Subendocardial Ischemia
False-Positive
ST depression without disease
False-Negative
Disease without ST depression
Silent Myocardial ischemia
Subendocardial InfarctionPersistent ST depression
T wave inversion
Subendo-cardial Infarction
Non-Specific ST-T changes
Subtle changes
slight flattening of T wave
minimal T wave inversion
FYI
Prinzmetal’s 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