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