E2: MI And Infarction

Question 1

What are the characteristics of a normal Q wave?

Answer 1

• The first part of the QRS complex and the first negative deflection following the PR segment
• Amplitude is <25% of the R wave and duration is <0.04 seconds

Question 2

Are normal T waves symmetrical?

Answer 2

No, the upstroke of a normal T wave is less steep than the downstroke

Question 3

What are the common causes of myocardial ischemia?

Answer 3

Atherosclerosis, vasospasms, thrombosis, embolism, decreased ventricular filling time, decreased filling pressure in coronary arteries

Question 4

What causes myocardial injury?

Answer 4

Results if ischemia progresses unresolved or untreated. Injury is a greater degree of cell damage than ischemia, but without actual cell death
-ST-T wave changes will be present

Question 5

What are the characteristic signs of myocardial ischemia?

Answer 5

• Inverted T waves
• Tall and peaked T waves
• Depressed ST segment

Question 6

What happens in transmural ischemia?

Answer 6

• Ischemia involving the entire myocardial wall
• repolarization reverses direction and becomes endocardium to epicardial, resulting in T wave inversion in leads overlying the ischemic regions
• T waves are symmetric

Question 7

When do peaked T waves occur?

Answer 7

May be seen in the earl stages of acute MI

Question 8

When is ST segment depression significant?

Answer 8

If >1mm below baseline measured 0.04 s to the right of the J point in two or more contiguous leads

Question 9

What is subendocardial ischemia?

Answer 9

Involves the inner layers of the heart, but does not extend through the entire ventricular wall
-Progressive subendocardial ischemia and injury may progress to subendocardial MI, also called Non-Q wave infarction

Question 10

What can cause flat ST segment depression?

Answer 10

Subendocardial injury or infarction

Question 11

What does ST segment elevation indicate and when is it significant?

Answer 11

• Indicates myocardial injury and may indicate that infarction is in progress
• Significant is ST segment is >1mm above baseline measured 0.04s to the right of J point in 2 or more contiguous leads

Question 12

Other than MI, when can ST segment elevation be seen?

Answer 12

-Ventricular hypertrophy
-conduction abnormalities
-pulmonary embolism
-Spontaneous pnuemothorax
-intracranial hemorrhage
-Hyperkalemia
Pericarditis

Question 13

What EKG finding is characteristic of pericarditis?

Answer 13

Diffuse ST segment elevation, except aVR will have depression

Question 14

What do pathologic Q waves indicate?

Answer 14

Presence of irreversible myocardial damage or MI

Question 15

What is the criteria for Q waves to be pathologic?

Answer 15

• > 0.04s duration
• At leas 1/3 the height of the R wave in the same QRS complex
• AND present in 2 or more leads

Question 16

What does it mean if there is a Q wave infarct?

Answer 16

Transmural infarct and more extensive damage

Question 17

What does it mean if there is a non-Q wave infarct?

Answer 17

-Subendocardial and less extensive damage

Question 18

How can you recognize a non-Q wave MI?

Answer 18

• Evolving St segment and T wave changes without Q waves

- Patients with typical chest pain symptoms and elevation of cardiac enzymes

Question 19

What part of the heart does the RCA perfuse?

Answer 19

The right atrium, right ventricle, and inferior and posterior walls of the LV

Question 20

What are the two branches off the LCA?

Answer 20

Left anterior descending (LAD) and left circumflex (LCX)

Question 21

What part of the heart does the LAD perfuse?

Answer 21

Anterior and lateral left ventricle, anterior 2/3 of the ventricular septum, and R and L bundle branches

Question 22

What part of the heart does the LCX perfuse?

Answer 22

Left atrium, anterolateral, posterolateral, and posterior LV

Question 23

What will you see on EKG if there is an anterior MI?

Answer 23

-Changes in precordial leads (V1-V4) with reciprocal changes in inferior leads

Question 24

What are the different types of anterior MI?

Answer 24

Septal (V1-2), anteroseptal (V1-3), and anterolateral (V1 or V2 to V5 or V6)

Question 25

What will you see on EKG if there is a lateral MI?

Answer 25

Changes in lead I, aVL, V5-6, with reciprocal changes in the inferior leads

Question 26

What will you see on EKG if there is an inferior MI?

Answer 26

Changes in leads II, III, and aVF with reciprocal changes in anterolateral leads

Question 27

What will you see on EKG if there is a posterior MI?

Answer 27

Reciprocal changes in V1-2 with tall R waves and ST depression in these leads

Question 28

On EKG, you see ST segment elevation, T wave inversion, and development of pathologic Q waves in leads V1-V4. What should you be suspicious of?

Answer 28

Anterior MI

Question 29

On EKG, you see ST segment elevation, T wave inversion, and development of pathologic Q waves in leads I, aVL, V5, and V6. What should you be suspicious of?

Answer 29

Lateral MI

Question 30

What leads are affected in a septal MI?

Answer 30

V1-2

Question 31

What leads are affected in anteroseptal MI?

Answer 31

V1-3

Question 32

What are the lateral leads on an EKG?

Answer 32

I, aVL, V5, and V6

Question 33

On EKG, you see ST segment elevation, T wave inversion, and development of pathologic Q waves in leads II, III, and aVF. What should you be suspicious of?

Answer 33

Inferior MI

Question 34

What are the inferior leads?

Answer 34

II, III, aVF

Question 35

How can you differentiate a new vs old MI?

Answer 35

-an old MI will have normalized ST segment and T waves, but with a pathologic Q wave

Question 36

What should you look for on EKG if you are suspicious for posterior MI?

Answer 36

Reciprocal changes in leads V1 and V2

Question 37

What are the criteria for a posterior MI?

Answer 37

Abnormal R waves in V1 and V2 fulfill the following criteria:

• Duration ≥ 0.04 sec
• R ≥ S
• Patient >30 yo

No signs of RVH