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Troponin test
Definition
The troponin test measures the levels of certain proteins called troponin T and troponin I in the blood. These proteins are released when the heart muscle has been damaged, such as 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.
Alternative Names
TroponinI; TnI; TroponinT; TnT; Cardiac-specific troponin I; Cardiac-specific troponin T; cTnl; cTnT
How the Test is Performed
A blood sample is needed. For information on how this is done, see: Venipuncture
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 determine if chest pain is due to 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.
Normal Results
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.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. 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 fast heart beat
- High blood pressure in lung arteries (pulmonary hypertension)
- Blockage of a lung artery by a blood clot, fat, or tumor cells (pulmonary embolus)
- Congestive heart failure
- Coronary artery spasm
- Inflammation of the heart muscle usually due to a virus (myocarditis)
- Strenuous exercise (for example, due to marathons or triathlons)
- 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
Risks
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)
Considerations
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.
References
AndersonJL. ST segment elevation acute myocardial infarction and complications of myocardial infarction. In: Goldman L, Schafer AI, eds.Cecil Medicine. 24th ed.Philadelphia,PA: Saunders Elsevier; 2011:chap 73.
Kushner FG, et al. 2009 Focused Updates:ACC/AHA Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction (Updating the 2004 Guideline and 2007 Focused Update) and ACC/AHA/SCAI Guidelines on Percutaneous Coronary Intervention (Updating the 2005 Guideline and 2007 Focused Update).Circulation. 2009;120:2271-2306.
Patil H, Vaidya O and Bogart D. A review of causes and systemic approach to cardiac troponin elevation.Clin Cardiol. 2011 Dec;34(12):723-8.
Sabatine MS, Cannon CC. Approach to the patient with chest pain. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds.Bonow: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine.9th ed. Saunders; 2011:chap 53.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Michael A. Chen, MD, PhD, Assistant Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
