Cardiac Enzyme Studies
Cardiac enzyme studies measure the
levels of enzymes and proteins that are linked with injury of the heart muscle. These include the enzymes creatine phosphokinase (CPK) and creatine kinase (CK), and
the proteins troponin I (TnI) and troponin T (TnT). Low levels
of these enzymes and proteins are normally found in your blood, but if your
heart muscle is injured, such as from a
heart attack, the enzymes and proteins leak out of
damaged heart muscle cells, and their levels in the bloodstream rise.
Because some of these enzymes and proteins are also found in other body
tissues, their levels in the blood may rise when those other tissues are
damaged. Cardiac enzyme studies must always be compared with your symptoms,
your physical examination findings, and
electrocardiogram (EKG, ECG) results.
Why It Is Done
Cardiac enzyme studies are done
- Determine whether you are having a heart attack
or a threatened heart attack (unstable angina) if you have chest
pain, shortness of breath, nausea, sweating, and abnormal electrocardiography
- Check for injury to the heart after
- Determine if a procedure,
such as percutaneous coronary intervention (PCI), or a medicine to dissolve the
blockage (thrombolytic medicine) has successfully restored blood flow through a
blocked coronary artery.
How To Prepare
No special preparation is required
before having this test.
Many medicines may affect the results of
this test. Be sure to tell your doctor about all the
nonprescription and prescription medicines you take.
Talk to your
doctor about any concerns you have regarding the need for the test, its risks,
how it will be done, or what the results will mean. To help you understand
the importance of this test, fill out the
medical test information form(What is a PDF document?).
How It Is Done
The health professional drawing your
- Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
- Remove the band from your arm when enough blood is
- Put a gauze pad or cotton ball over the needle site as
the needle is removed.
- Put pressure on the site and then put on a
Cardiac enzyme studies are often repeated over several
hours for comparison. Blood samples for these cardiac enzyme tests are usually
drawn every 8 to 12 hours for 1 to 2 days after a suspected heart attack, to
look for the rise and fall in the enzyme levels.