Test Overview

Cardiac enzyme studies measure the levels of enzymes and proteins that are linked with injury of the heart muscle. The test checks for the proteins troponin I (TnI) and troponin T (TnT). The test might also check for an enzyme called creatine kinase (CK). Low levels of these proteins and enzymes are normally found in your blood, but if your heart muscle is injured, such as from a heart attack, the proteins and enzymes leak out of damaged heart muscle cells, and their levels in the bloodstream rise.

Because some of these proteins and enzymes 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 to:

• Determine whether you are having a heart attack or acute coronary syndrome if you have symptoms such as chest pain, shortness of breath, nausea, sweating, and abnormal electrocardiography results.
• Check for injury to the heart from other causes, such as an infection.

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 non-prescription 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.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

Cardiac enzyme studies are often repeated over several hours for comparison.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Higher-than-normal levels of cardiac enzymes and proteins may mean that the heart muscle was damaged.

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.