Cardiac enzymes

Question 1

MI

Answer 1

• Temporary diminished supply of blood to myocardium –> reversible effects
• 1 cause of chest pain

Question 2

MI cause

Answer 2

Obstruction or constriction of coronary vessels

Question 3

Myocardial ischemia

Answer 3

May develop:

1. Slowly as aa become obstructed over time
2. Quickly when artery becomes suddenly obstructed

Question 4

Myocardial ischemia causes

Answer 4

• Coronary artery disease = most common
• Blood clot
• Coronary artery spasm

Question 5

CAD

Answer 5

• Plaques comprised of cholesterol which builds up in arterial wall
• Blood flow restricted &/or rupture of plaques –> blood clot

Question 6

Blood clot

Answer 6

• Plaque builds up, ruptures –> localized clot

- May travel to coronary aa from another area of body (rare)

Question 7

Coronary artery spasm

Answer 7

Arterial wall spasm –> temporary interruption of blood flow

Question 8

MI sx

Answer 8

• Chest pain
• Dyspnea
• Nausea
• Pain radiating to neck, arms, back
• Epigastric pain
• Fatigue/ weakness
• Dizziness
• Impeding sense of doom

Question 9

What type of patients present atypically w/ an MI?

Answer 9

• Elderly
• Females
• Diabetics

Question 10

Acute MI

Answer 10

Myocardial cell death due to prolonged ischemia

Question 11

Tall T waves

Answer 11

• Earliest change seen in acute MI

- Most often seen in anterior chest leads

Question 12

Flattened T waves

Answer 12

Often seen in pts w/ myocardial ischemia, but often non-specific

Question 13

Q waves

Answer 13

Typically seen in left-sided leads

Question 14

Pathological Q waves

Answer 14

• > 40 ms wide
• > 2 mm
• 25% of depth of QRS
• Seen in leads V1-3

Question 15

Pathological Q wave differential

Answer 15

• MI
• Cardiomyopathies
• Rotation of heart
• Lead placement errors

Question 16

Intracellular enzymes & proteins

Answer 16

• Creatine kinase (CK or total CK)
• Creatine kinase myoglobin (CK-MB)
• Myoglobin (MB)
• Troponin **

Question 17

CK

Answer 17

Released w/ brain or muscle injury

Question 18

What are the 3 isoenzymes of CK?

Answer 18

Total CK:

• CK-MB in heart
• CK-MM in muscle
• CK-BB in brain

Question 19

CK-MB may also present where?

Answer 19

• Small intestine
• Tongue
• Diaphragm
• Uterus
• Prostate

Question 20

When does CK-MB increase?

Answer 20

4-6 hrs after myocardial injury

Question 21

When does CK-MB peak?

Answer 21

18-24 hrs

Question 22

When does CK-MB normalize?

Answer 22

48-72 hrs

Question 23

What is the normal range of CK-MB?

Answer 23

5-25

Question 24

When is CK-MB most sensitive/specific to MI?

Answer 24

Within 24-36 hrs of onset of chest pain

Question 25

MB

Answer 25

- Protein found in skeletal & cardiac muscle - Lower sensitivity - Considered unnecessary w/ troponin testing

Question 26

When does MB increase?

Answer 26

2-4 hrs after myocardial injury

Question 27

When does MB peak?

Answer 27

6-12 hrs

Question 28

When does MB normalize

Answer 28

24-36 hrs

Question 29

What is the normal range for MB?

Answer 29

0-85

Question 30

Troponin categories

Answer 30

- Troponin I (TnI) - Troponin T (TnT) - Troponin C (TnC) * All regulatory proteins part of skeletal & cardiac muscle * Each has unique fxn

Question 31

Which troponin inhibits the interaction of myosin w/ actin?

Answer 31

Troponin I

Question 32

Which troponin binds troponin components to tropomyosin?

Answer 32

Troponin T

Question 33

Which troponin contains the binding sites for Ca2+?

Answer 33

Troponin C | - Initiates contraction

Question 34

Which troponins are immunologically distinct enzymes?

Answer 34

I & C

Question 35

Which troponin has the greatest sensitivity for MI?

Answer 35

Troponin I - Detects small infarcts, myocardial injury - May be elevated for other reasons other than MI

Question 36

When does troponin I increase?

Answer 36

4-8 hrs

Question 37

When does troponin I peak?

Answer 37

18-24 hrs

Question 38

When does troponin I normalize?

Answer 38

5-14 days

Question 39

What is normal troponin I?

Answer 39

<0.1

Question 40

What range of troponin I is considered indeterminate?

Answer 40

.1-.9

Question 41

What range of troponin I is myocardial injury likely?

Answer 41

1.0-1.4

Question 42

W/ troponin I, what level is definitive for myocardial injury?

Answer 42

> or = to 1.5

Question 43

Which cardiac enzymes are more accurate & sensitive? Serial markers or single initial?

Answer 43

Serial markers - 4 to 6 hr intervals X 3 - Utilized less in unstable angina