Hughes & Jefferson Ch9. Markers of Cardiac and Muscle Injury and Disease Flashcards
Cytosolic enzyme that facilitates the mitochondrial transfer of high-energy phosphates from the cytoplasm.
Creatine kinase (CK)
Creatine kinase (CK) is a _______ that _______ the ________________ from the cytoplasm.
cytosolic enzyme, facilitates, mitochondrial transfer of high energy phosphates
Three potential isoenzymes of CK
MM, MB, BB
True or False: CK is widely distributed but found predominantly in brain tissue.
False. CK is found predominantly in muscle.
Skeletal muscle contains approximately 99% _______ and 1% _______.
CK-MM, CK-MB
The amount of CK-MB in skeletal muscle increases during injury due to __________.
muscle fiber regeneration
Cardiac monocytes contain 20-30% _______, with the remainder being _______.
CK-MB, CK-MM
The CK-BB isoform is found in other organs such as the ________, and is not routinely measured.
brain
Normally, ________ accounts for more than 95% of circulating CK.
CK-MM
The normal level of total CK is _______ in males, and _______ in females.
~55-170 U/L, ~30-135 U/L
Individuals with larger muscles typically have (higher/lower) levels of total CK.
higher
True or False: Relative specificity of CK-MB for myocardial tissue is useful in the investigation of suspected cardiac disease.
True
In order to confirm a diagnosis of acute MI, a ________ increase is required with an increase in CK-MB fraction.
So, if normal CK-MB level is roughly 0-5 ng/mL, CK-MB level in acute MI is ________.
2-fold, >9 ng/mL
The ratio of CK-MB to total CK can also be measured to determine cardiac disease.
What ratio of CK-MB to total CK suggests a cardiac source?
> 2.5
CK levels usually increase by _______ following MI, peak at ________, and fall to normal by ________.
4-6 hrs, 18-24 hrs, 36-48 hrs
Common markers of MI (4)
Creatine Kinase (total and CK-MB)
Troponins (cTnI, cTnT)
Lactate Dehydrogenase (LDH)
Myoglobin
True or False: CK alone is enough to diagnose a small MI or a microinfarct. Moreover, CK levels increase during an episode of angina or pericarditis.
False. CK is not as sensitive as troponins and may not detect a small MI with limited myocardial injury or microinfarct.
CK levels also do not increase during episodes of angina or pericarditis.
True or False: increased CK-MB levels can be observed in muscle injury with regenerating fibers, and the typical acute rise and fall of CK-MB levels occur as it does in MI.
False. While it is correct that CK-MB levels increase in muscle injury with regenerating fibers, as in marathon runners and rhabdomyolysis patients, the acute rise and fall of CK-MB levels DOES NOT occur.
A cardiac cause for a raised CK level is suggested by: (4)
Clinical history of chest pain
Typical time course (rise and fall of CK levels)
Raised CK-MB level (>9 ng/mL)
Increased ratio of CK-MB : total CK (>2.5)
Does total quantity of CK released have a relationship with the infarct size?
Yes. Total CK released correlates with infarct size. The higher the amount of CK released, the larger the infarct size.
[Assessment of coronary artery reperfusion]
True or False: The peak CK level reflects how quickly the enzyme is cleared from the injured myocardium and is less closely linked to infarct size.
True.
Successful reperfusion, such as after angioplasty or thrombolysis, causes an early rise in CK-MB with a shorter duration because the enzyme is quickly “washed out” from the damaged heart area.
Why is CK-MB used in the diagnosis of an additional MI or extension of the original infarct instead of troponin?
Since CK-MB levels decrease shortly after acute MI, if the levels suddenly increase again, it can be an indicator of an additional MI or extension of the original MI. Troponin levels remain elevated for a prolonged period after MI, so while it permits late diagnosis, it cannot detect an additional MI or an extension of the original MI.
Non-cardiac causes of raised CK levels:
Skeletal muscle injury (myopathies)
Brain injury (stroke)
Hypothyroidism
Structural proteins present within cardiac myocytes involved in the interaction between contractile proteins actin and myosin.
Troponins