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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.
Cardiac enzyme studies are done to:
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 nonprescription 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. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).
The health professional drawing your blood will:
Cardiac enzyme studies are often repeated over several hours for comparison.
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having a blood sample taken from a vein.
Cardiac enzyme studies measure the levels of the proteins troponin I (TnI) and troponin T (TnT) and the enzyme creatine kinase (CK) in the blood.
Values and units for reporting the results of cardiac enzyme tests vary considerably. The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Troponin normal values:footnote 1
CK-MB (creatine kinase-myocardial band) normal values:footnote 1
Reasons you may not be able to have the test or why the results may not be helpful include:
CK-MB, which is found in large amounts in damaged heart muscle is a more specific way to estimate the amount of heart muscle damage than total CK. The total CK enzyme level can be elevated from vigorous exercise, intramuscular injections, crush injuries to muscles, muscular dystrophy, or muscle inflammation.
CitationsFischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.Other Works ConsultedChernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.Pagana KD, Pagana TJ (2014). Mosby's Manual of Diagnostic and Laboratory Tests, 5th ed. St. Louis: Mosby.Thygesen K, et al. (2012). Third universal definition of myocardial infarction. Circulation, 126(16): 2020–2035. Also available online: http://circ.ahajournals.org/content/126/16/2020.
ByHealthwise StaffPrimary Medical ReviewerRakesh K. Pai, MD, FACC - Cardiology, ElectrophysiologyE. Gregory Thompson, MD - Internal MedicineMartin J. Gabica, MD - Family MedicineAdam Husney, MD - Family MedicineSpecialist Medical ReviewerGeorge Philippides, MD - Cardiology
Current as ofFebruary 23, 2018
Current as of: February 23, 2018
Author: Healthwise Staff
Medical Review: Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & E. Gregory Thompson, MD - Internal Medicine & Martin J. Gabica, MD - Family Medicine & Adam Husney, MD - Family Medicine & George Philippides, MD - Cardiology
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