Cardiac Enzymes

Question 1

What are the cardiac enzyme markers?

Answer 1

1. Creatine Kinase (CK)
A. Total
B. CK-MB
2. Troponin T
3. Troponin I

Question 2

What are the normal ri for total Creatine kinase?

Answer 2

1. Adult/elderly
A. Male : 55 – 170 units/L 
B. Female : 30 – 135 units/L
2. Newborn: 65 – 580 units/L
3. Values higher after exercise

Question 3

What are the indications for testing creating kinase?

Answer 3

1. Used to support diagnosis of myocardial infarction

2. Can also indicate neurologic or skeletal muscle diseases

Question 4

Where is creatine kinase located?

Answer 4

Heart muscle
Skeletal muscle
Brain

Question 5

Why is creatine kinase used as a clinical marker?

Answer 5

Elevation occurs when muscle or nerve cells are injured

Question 6

What is the timing of creatine kinase elevation?

Answer 6

Rise within 6 hours
Peak @ 18 hours
Back to baseline 2 -3 days

Question 7

What is an isoenzyme?

Answer 7

One of a group of enzymes that are very similar in catalytic properties but differ by variations in physical properties:
A. Isoelectric point
B. Electrophoretic mobility

Question 8

What are the creatine kinase isoenzymes? How are they differentiated?

Answer 8

CK BB (CK 1)
CK MB (CK2): cardiac
CK MM (CK3)
Electrophoresis

Question 9

Where is creatine kinase BB located?

Answer 9

Brain
Lung
Think BB: Brain and Breathing

Question 10

What is Creatine BB a clinical marker of?

Answer 10

1. Diseases that affect the CNS
A. Stroke, brain injury, brain cancer, subarachnoid hemorrhage, seizures, shock
2. Pulmonary Infarction 
3. Adenocarcinoma of lung
4. Electroconvulsive therapy

Question 11

Where is creatine kinase MB located?

Answer 11

Myocardial Cells

Skeletal Muscle
Small amounts

MB: think myocardium and Body

Question 12

What is Creatine MB a clinical marker of?

Answer 12

Myocardial Infarction

Ventricular arrhythmia

Cardiac ischemia

Myocarditis

Cardiac surgery

Cardiac defibrillation

Question 13

What is the timing of elevation of creatine kinase MB?

Answer 13

1. Rise 3-6 hours after MI
2. Peaks 12- 24 hours
3. Back to baseline 12-48 hours after MI

Question 14

What are the clinical priorities for creatine kinase MB?

Answer 14

1. CK-MB helpful in quantifying:
   A. Degree of MI
   B. Onset of infarction

Question 15

Where is creatine kinase MM located?

Answer 15

Skeletal muscle
Varies according to a person’s muscle mass

CK-MM think Muscle Mass

Question 16

What is Creatine MM a clinical marker of?

Answer 16

Myopathies
Vigorous exercise
Multiple intramuscular injections
Electroconvulsive therapy
Cardioversion
Recent surgery
Crush injuries

Question 17

Which isoenzyme makes up the most of total creatine kinase

Answer 17

CK-MM

Question 18

What are the normal ranges of trop T?

Answer 18

<0.2 ng/ml

Question 19

What are the normal ranges of trop I?

Answer 19

<0.03 ng/ml

Question 20

What are some differences between Trop T and trop I?

Answer 20

Trop T remains elevated longer than Trop I; also Trop T generally has a higher peak than Trop I

Question 21

What are the indications for troponin testing?

Answer 21

1. Blood assay performed on patients who present with chest pain
   A. Specific indicator of cardiac muscle injury
   -Rule in or rule out cardiac ischemia
2. Helpful in predicting clinical outcome of patient with acute myocardial infarction
   A. Higher the level, the more significant the injury to cardiac muscle

Question 22

How can skeletal muscle troponins be separated from cardiac troponins?

Answer 22

use of monoclonal antibodies or enzyme-linked immunosorbant assays (ELISA)

Question 23

Why are troponin levels measured?

Answer 23

Troponins are proteins that exist in skeletal and cardiac muscle
Regulate calcium dependent interaction of myosin with actin for muscle contraction

Question 24

What are cardiac troponins similar to?

Answer 24

CK-MB

Question 25

What are cardiac troponins specific for?

Answer 25

1. cardiac troponins are highly specific for myocardial cell injury:

A. Cardiac troponins will always be normal in noncardiac disease

B. Cardiac troponins become elevated sooner and remain elevated longer than CK-MB

C. Cardiac troponins are more sensitive to cardiac muscle injury than CK-MB

Question 26

What is the timing of elevation for cardiac troponins?

Answer 26

1. Elevate as early as three hours after myocardial injury
2. Troponin I can remain elevated for 7-10 days after myocardial infarction
3. Troponin T can remain elevated for 10-14 days after event

Question 27

Why are cardiac troponins not useful in diagnosing recurrent MI?

Answer 27

1. Due to the longer period of time that troponins are elevated, they are not useful in diagnosing recurrent MI
   A. May be elevated from first cardiac event

Question 28

What is the clinical significance of cardiac troponins?

Answer 28

1. Cardiac vs noncardiac chest pain
   A. Helpful when EKG and CK-MB results are not classic for myocardial infarction
   B. Unstable angina may have slightly elevated troponins
   C. If cardiac troponin is normal, chest pain is noncardiac

Question 29

How are cardiac troponins useful in estimation of MI size?

Answer 29

Elevated troponin levels at four weeks post MI are inversely proportional to left ventricular ejection fraction: low ejection fraction due to massive MI

Question 30

How are cardiac troponins useful in detection of reperfusion associated with coronary recanalization?

Answer 30

“Washout” or second peak of cardiac troponin accurately indicates reperfusion after a stent is placed to open up an artery

Question 31

How are cardiac troponins useful in detection of peri-operative MI?

Answer 31

1. Since cardiac troponins are not affected by skeletal muscle injury, they are a good indicator of myocardial infarction in the perioperative period
2. CK MB may be elevated secondary to skeletal muscle injury

Question 32

When are troponin levels falsely elevated?

Answer 32

Dialysis pts