Cardiac Enzymes-Diagnostics

Question 1

Ischemia

Answer 1

• Temporary diminished supply of blood (oxygen and nutrients) to the myocardium resulting in reversible effects
• Due to obstruction or constriction of the coronary vessels supplying the myocardium

Question 2

Myocardial Ischemia

Answer 2

-Ischemia may develop slowly as arteries become obstructed over time or it can occur quickly when an artery becomes suddenly obstructive

Question 3

Causes of an MI

Answer 3

• Coronary artery disease
• Blood clot
• Coronary artery spasm

Question 4

CAD

Answer 4

• Most common cause of ischemia
• Plaques comprised mostly of cholesterol which build up in arterial wall
• Blood flow restricted by build up of plaques and/or rupture of plaques which can result in blood clot

Question 5

Blood clot

Answer 5

• Plaque build up ruptures which results information of localized clot
• Blood clot may travel to the coronary arteries from another area of the body= rare

Question 6

Coronary artery spasm

Answer 6

-Arterial wall spam resulting in in temporary interruption of blood flow

Question 7

Acute MI

Answer 7

-Myocardial cell death due to prolonged ischemia

Question 8

Histological cell death

Answer 8

-Takes about 20 minutes

Question 9

Complete necrosis of myocardial cells

Answer 9

=2-4 hrs

Question 10

ST depression greater than or equal to 1 mm

Answer 10

-More specific and coveys worse prognosis

Question 11

ST depression greater than or equal to 2 mm in greater than or equal to 3 leads

Answer 11

• Associated with a high probability of NSTEMI and predicts significant mortality
• ->35% mortality @ 30 days

Question 12

ST elevation

Answer 12

-ST elevation @ the J point in 2 contiguous leads or more of 0.2 mV or more in males or 0.15 mV ore more in females in leads V2-V3

Question 13

Tall T waves

Answer 13

• earliest changes seen in acute MI

- Most often seen in the anterior chest leads

Question 14

Isolated tall T waves

Answer 14

• In leads V1-V3 may be due to ischemia of posterior wall of the left ventricle
• ->the mirror image of T wave inversion

Question 15

Creatine Kinase

Answer 15

-An enzyme released with muscle or brain tissue injury

Question 16

Total CK

Answer 16

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

Question 17

CK-MB

Answer 17

• Begins to increase 4-6 hrs after myocardial injury
• Peaks in 18-24 hrs
• Normalizes in 48-71 hrs

Question 18

Troponin I

Answer 18

Inhibits the interaction of myosin with actin

Question 19

Troponin T

Answer 19

Binds the troponin components to Tropomyosin

Question 20

Troponin C

Answer 20

Contains the binding sites for the Ca2+ that helps initiate contraction

Question 21

Troponin-I

Answer 21

-Greatest sensitivity for myocardial injury

Question 22

Troponin-I onset

Answer 22

-Begin to increase 4-8 hrs after an MI

Question 23

Troponin-I Peak

Answer 23

@ 18-24 hrs

Question 24

How long does a Troponin-I stay elevated?

Answer 24

5-14 days

Question 25

Myoglobin (MB)

Answer 25

Protein found in skeletal and cardiac muscle

Question 26

When does MB increase?

Answer 26

2-4 hrs after myocardial injury
=Peaks the earliest!
–>diminished utility due to lower sensitivity

Question 27

When is the CK-MB the most sensitive and specific for myocardial injury?

Answer 27

when measured w/in 24-36 hrs of the onset of chest pain

Question 28

Pathological Q Waves

Answer 28

> 1 mm wide
2 mm deep
Seen in leads V1-V3