The troponin test measures the levels of one of two proteins, troponin T or troponin I, in a blood sample. These proteins are released when the heart muscle has been damaged, such as during a heart attack. The more damage there is to the heart, the greater the amount of troponin T and I there will be in the blood.
TroponinI; TnI; TroponinT; TnT; Cardiac-specific troponin I; Cardiac-specific troponin T; cTnl; cTnT
How the test is performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
The sample is sent to a laboratory where the levels of troponins are measured.
How to prepare for the test
Usually, no special preparation is necessary.
How the test will feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
The most common reason to perform this test is to diagnose a heart attack. Your doctor will order this test if you have chest pain and signs of a heart attack. The test is usually repeated two more times over the next 12 to 16 hours.
Your doctor may also order this test if you have angina that is getting worse, but no signs of a heart attack.
The troponin test may also be done to help detect and evaluate other causes of heart injury.
The test may be done along with other cardiac marker tests, such as CPK isoenzymes or myoglobin.
Cardiac troponin levels are normally so low they cannot be detected with most blood tests.
Your test results are usually considered normal if the results are:
- Troponin I : less than 10 µg/L
- Troponin T : 0–0.1 µg/L
Normal troponin levels 12 hours after chest pain has started mean a heart attack is unlikely.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
An increase in the troponin level, even a slight one, usually means there has been some damage to the heart. Significantly high levels of troponin are a sign that a heart attack has occurred.
Most patients who have had a heart attack have increased troponin levels within 6 hours. After 12 hours almost everyone who has had a heart attack will have raised levels.
Troponin levels may remain high for 1 to 2 weeks after a heart attack.
Increased troponin levels may also be due to:
- Abnormally high blood pressure in lung arteries (pulmonary hypertension)
- Blockage of a lung artery by a blood clot, fat, or tumor cells (pulmonary embolus)
- Coronary artery spasm
- Inflammation of the heart muscle usually due to a virus (myocarditis)
- Severe gastrointestinal bleeding
- Severely rapid heart beat (for example, due to supraventricular tachycardia)
- Strenuous exercise (for example, due to marathons or triathlons)
- Sudden worsening of chronic obstructive pulmonary disease
- Trauma that injures the heart such as a car accident
- Weakening of the heart muscle (cardiomyopathy)
- Increased troponin levels may also result from certain medical procedures such as:
- Cardiac angioplasty/stenting
- Heart defibrillation or electrical cardioversion (purposeful shocking of the heart by medical personnel)
- Open heart surgery
- Radiofrequency ablation of the heart
What the risks are
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Increased troponin levels may also be seen in people with certain chronic health conditions such as heart failure, long-term kidney disease, and stable heart disease. Increased levels in these and other conditions can be a sign that a patient is at increased risk for bad outcomes.
Antman EM. ST-Elevation myocardial infarcation: management. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Libby: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Saunders; 2007:chap 51.
Antman EM, Hand M, Armstrong PW, et al. 2007 Focused Update of the ACC/AHA 2004 Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines: developed in collaboration With the Canadian Cardiovascular Society endorsed by the American Academy of Family Physicians: 2007 Writing Group to Review New Evidence and Update the ACC/AHA 2004 Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction, Writing on Behalf of the 2004 Writing Committee. Circulation. 2008 Jan 15;117(2):296-329.
Brady WJ, Harrigan RA, Chan TC. Acute Coronary Syndrome. In: Marx JA, ed. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 76.
David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., and Michael A. Chen, MD, PhD, Assistant Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, Washington.
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