Ischemia/Infarction (Exam #2)

Question 1

What is the “path” of depolarization in heart tissue?

Answer 1

Endocardial → Epicardial (inner to outer)

Question 2

What is the “path” of repolarization in heart tissue?

Answer 2

Epicardial → Endocardial (outer to inner)

Question 3

Define Myocardial Ischemia. What general changes are seen (2)?

Answer 3

Ischemia = REVERSIBLE cell damage due to decreased O2

• ST segment changes
• T wave changes

Question 4

What are the three criteria for Myocardial Ischemia (__ OR __ OR __)?

Answer 4

- ST segment depression
OR 
- T wave inversion
OR 
- Peaked/Symmetrical T waves

Question 5

Define Myocardial Injury. What general changes are seen?

Answer 5

Injury = prolonged ischemia → further cell damage but NO cell death
- ST segment changes

Question 6

What is the primary criteria for Myocardial Injury?

Answer 6

ST segment elevation

Question 7

What other condition presents with T wave inversion, and how can you differentiate it from Transmural Ischemia?

Answer 7

Strain presents with T wave inversion but they are asymmetrical
- Transmural Ischemia = T wave inversion and SYMMETRICAL

Question 8

What is seen with Subendocardial Ischemia?

Answer 8

Transient ST segment depression

Question 9

What is seen with Transmural Ischemia?

Answer 9

Transient ST segment elevation

Question 10

What causes the T wave inversion seen with Myocardial Ischemia?

Answer 10

Delayed repolarization

Question 11

What causes the T wave changes seen when Subendocardial Ischemia progresses to Transmural Ischemia?

Answer 11

Reversal of repolarization causes T wave to invert and become symmetrical

Question 12

What other condition presents with ST segment elevation, and how can you differentiate it from Myocardial Injury?

Answer 12

Pericarditis presents with DIFFUSE ST segment elevation

- Injury presents in respective leads (not diffuse)

Question 13

Define Myocardial Infarction. What general changes are seen?

Answer 13

Infarction = cell death, enzymes released (T)

- Pathologic Q waves

Question 14

What causes the development of pathologic Q waves?

Answer 14

Infarcted tissue is electrically silenced

Question 15

What are the criteria for Q waves (__ AND __ AND __), and when do these present?

Answer 15

Myocardial Infarction
- 0.04+ seconds in duration
AND
- At least 1/3 the height of R waves in same QRS complex
AND
- Present in 2+ contiguous leads

Question 16

How can you differentiate Ischemia from Infarction (non-EKG)?

Answer 16

Elevated Troponin (T) with Myocardial Infarction

Question 17

How can you differentiate an NSTEMI from a STEMI?

Answer 17

• NSTEMI = ST segment changes + T wave changes (NO Q waves)

- STEMI = ST segment changes + T wave changes + Q waves

Question 18

In what three leads does an Anterior MI present?

Answer 18

V2, V3 and V4

- V1 NOT INVOLVED

Question 19

What type of MI presents in V2, V3 and V4?

Answer 19

Anterior MI

Question 20

In what two leads does a Septal MI present?

Answer 20

V1 and V2

Question 21

What type of MI presents in V1 and V2?

Answer 21

Septal MI

Question 22

In what three leads does an Anterolateral MI present?

Answer 22

V4, V5 and V6

Question 23

What type of MI presents in V4, V5 and V6?

Answer 23

Anterolateral MI

Question 24

In what four leads does a Lateral MI present?

Answer 24

I, aVL, V5 and V6

Question 25

What type of MI presents in I, aVL, V5 and V6?

Answer 25

Lateral MI

Question 26

In what three leads does an Inferior MI present?

Answer 26

II, III and aVF

Question 27

What type of MI presents in II, III and aVF?

Answer 27

Inferior MI

Question 28

What are the two criteria for a Posterior MI (hint: be specific with the R waves)?

Answer 28

Reciprocal changes in V1 and V2 - Abnormal R waves in V1 and V2 (0.04+ seconds in duration, R > S, patient is 30+ years old) - ST segment depression

Question 29

How can you differentiate a NEW MI from an OLD MI?

Answer 29

- New = ST segment changes + T wave changes + Q waves | - Old = Q waves only

Question 30

What should you suspect if you see ST depression in V1, V2 and V3 with NO other ST elevation in other leads?

Answer 30

Posterior MI

Question 31

What finding on EKG is suspicious for Posterior MI?

Answer 31

ST depression seen in V1, V2 and V3 with NO other ST elevation in other leads