When the heart suffers an injury it releases certain enzymes. Elevated cardiac enzyme levels indicate a person has had a heart attack.

Enzymes are proteins produced by the body to speed up specific chemical reactions in the body. The cardiac enzymes that doctors measure to see if a person is having a heart attack include troponin T (TnT) and troponin I (TnI).

Both troponin types are commonly checked because they are the most specific enzymes to a heart attack. Doctors may also check the levels of creatine phosphokinase (CPK) and myoglobin in some situations.

These enzymes are normally present in low quantities in the bloodstream. When these levels are elevated, it indicates that the heart muscle may be injured or may not be getting enough oxygen.

In this article, we take a look at the cardiac enzyme test and the possible causes behind elevated cardiac enzyme levels. We also look at what treatments may be required if someone has high cardiac enzyme levels.

A cardiac enzyme test is a blood test that measures the cardiac enzymes in the blood. A technician will insert a needle into a person’s arm and draw a sample of blood. They will send the sample to a lab where it will be analyzed for cardiac enzymes.

People undergoing a cardiac enzyme test do not need to fast or undergo any special preparations. Doctors often order this test in an emergency situation when they suspect a person may be having a heart attack.

The results of a cardiac enzyme test can indicate if someone had a heart attack.

Levels of troponin are normally so low that this enzyme is undetectable in the blood. If someone’s cardiac enzyme test comes back positive for troponin, they have likely had a heart attack or injury to the heart.

The results of a cardiac enzyme test can also help a doctor to assess the level of damage caused by the heart attack. The more troponin found in the blood, the more damaged the heart generally is.

Doctors and scientists measure troponin in nanograms per milliliter (ng/mL). The more nanograms per milliliter found in the blood, the higher the likelihood of a heart attack.

A cardiac enzyme test may come back normal if the test is performed too soon after an injury to the heart. A doctor will generally repeat a cardiac enzyme test after several hours as a result.

There are a few other factors that may cause cardiac enzyme levels to be elevated.

These include the following:

  • pulmonary hypertension
  • tachycardia, where the heart beats faster than normal
  • pulmonary embolism, a blockage of an artery in the lungs
  • kidney disease
  • congestive heart failure
  • weakening of the heart muscle
  • injury or trauma to the heart muscle, such as from a car accident
  • prolonged exercise
  • swelling of the heart muscle
  • open heart surgery
  • cardiac stenting
  • cardiac ablation
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Medication is often prescribed following a cardiac enzyme test to prevent future heart attacks or treat heart damage.

A doctor will likely order other tests in addition to a cardiac enzyme test. This is because other factors besides heart attacks can cause high cardiac enzyme levels.

These tests may include the following:

  • other blood tests
  • electrocardiogram
  • echocardiogram
  • chest X-ray
  • angiogram
  • stress test
  • heart CT scan

If the reason for the elevated cardiac enzymes is not a heart attack, a doctor may treat whatever condition is causing the enzyme levels to be elevated. The doctor may also suggest that a person makes healthful lifestyle changes to keep the heart working as well as possible.

If a doctor determines that a heart attack caused the elevated cardiac enzymes levels, the person will require treatment in the hospital with medications or surgery to restore blood flow to the heart.

Doctors may also prescribe the following medications for a person who has had a heart attack:

  • drugs that dissolve blood clots, known as thrombolytics
  • blood thinners, such as heparin
  • antiplatelet agents to keep blood clots from getting bigger
  • nitroglycerin
  • beta-blockers
  • ACE inhibitors
  • pain medications

A doctor may recommend that a person who has just had a heart attack should have surgery in addition to treatment with medications. Doctors may suggest coronary stenting or coronary artery bypass surgery.

Coronary stenting

During this procedure, a doctor will guide a long thin tube through an artery to find blockages. When the doctor locates a blockage, they will use a tool on the end of the tube to open the blocked artery and insert a metal stent to keep the artery open.

The person who had the heart attack is normally awake or under light sedation. People require less recovery time after this procedure than after a coronary bypass.

Coronary bypass

A coronary artery bypass is major surgery that may occur immediately following a heart attack, or shortly after to give the heart a chance to recover.

During a coronary artery bypass, a doctor will remove a portion of the blocked artery and stitch the artery back together.

Heart attacks are a medical emergency. People who have high cardiac enzyme levels must follow all of their doctor’s instructions for the best outcomes. People who receive faster treatment also generally have better outcomes than those who wait for treatment.

The outlook for people varies based on what is causing the elevated enzyme levels. A doctor can advise a person on their specific outlook and the best ways to keep their heart as healthy as possible.