What does it mean when your heart enzymes are high?

— Milly, South Carolina

High levels of cardiac enzymes can mean a number of things, but they often signal some type of damage to the heart. Enzymes are proteins that promote specific biochemical reactions within cells. Key enzymes that work within heart muscle cells include troponin (TnI, TnT), which helps control how the heart muscles contract, and creatine phosphokinase (CPK, CK), which is a critical player in the heart’s energy management process.


Because cardiac enzymes generally operate within your heart, only low levels of these enzymes are normally found in your blood. But if your heart muscle is injured in some way — say, from a heart attack or even heart surgery — the enzymes then leak out of damaged heart-muscle cells, and their levels in the bloodstream rise. For this reason, if you're having specific symptoms or have undergone certain procedures, doctors often test the level of your cardiac enzymes.

There are a number of reasons why cardiac enzyme tests might be ordered. If you're having chest pain, shortness of breath, nausea, sweating, and abnormal electrocardiography (ECG) results, for instance, knowing your enzyme levels can help determine whether you are in the midst of a heart attack. Enzyme testing is also done to check for injury to the heart after some forms of cardiac surgery. During the recovery period following a heart attack or injury, such tests can also help determine whether a cardiac procedure or a medicine being used to dissolve a blockage (thrombolytic medicine) has successfully restored blood flow through a blocked coronary artery.

The results of these tests are not always completely clear-cut, however.

Because cardiac enzymes leak slowly into the bloodstream, high enzyme levels may not appear for six or more hours after the onset of a heart attack. For this reason, if someone is experiencing chest pain but their heart enzymes are normal, a heart attack cannot be completely ruled out. In such cases, repeated cardiac enzyme tests are normally conducted to confirm the diagnosis of a heart attack.

Additionally, because some heart enzymes are also found in other body tissues, such as the brain or skeletal muscle, their blood levels may rise when these other tissues are damaged.

Bottom line: You always need a doctor to analyze heart enzyme tests, and you may need more than one screening. To get a complete picture and determine the best treatment, your medical team will also take into consideration your symptoms, the findings from your physical examination, your electrocardiogram (EKG or ECG), and other tests. In most cases, high levels of cardiac enzymes are the result a heart attack — and measuring these enzymes is the gold standard for a heart attack diagnosis.

Learn more in the Everyday Health Heart Health Center.