Cardiac Enzyme Studies
How It Feels
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
There is very little chance of a problem from
having a blood sample taken from a vein.
- You may get a small bruise at the site. You can
lower the chance of bruising by keeping pressure on the site for several
- In rare cases, the vein may become swollen after the
blood sample is taken. This problem is called phlebitis. A warm compress can be
used several times a day to treat this.
- Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin) and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.
Cardiac enzyme studies measure the
levels of the
enzymes creatine phosphokinase (CPK) and creatine kinase (CK), and the proteins troponin I (TnI) and troponin T (TnT) in the blood.
and units for reporting the results of cardiac enzyme tests vary considerably. The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Troponin normal values:1
Total CPK (creatine phosphokinase) normal values:1
- 0–120 micrograms per liter (mcg/L)
CK-MB (creatine kinase) normal values:1
- 0–3 micrograms per liter (mcg/L)
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- Other diseases, such as
muscular dystrophy, certain
autoimmune diseases, and
- Other heart conditions,
myocarditis and some forms of
- Emergency measures to
treat heart problems, such as
CPR, cardioversion, or
- Medicines, especially injections into muscles (IM
- Cholesterol-lowering medicines
- Heavy alcohol use.
- Recent strenuous
surgery or serious injury.
What To Think About
- CPK-MB, which is found in large amounts in damaged heart
muscle is a more specific way to estimate the amount of heart muscle damage
than total CPK. The total CPK enzyme level can be elevated from vigorous
exercise, intramuscular injections, crush injuries to muscles, muscular
dystrophy, or muscle inflammation.
- Another protein,
myoglobin, may be tested along with cardiac enzymes to
diagnose a heart attack.