Blood tests confirm (or refute) suspicions raised in the early stages of evaluation typically in an emergency room, intensive care unit or urgent care setting. Such tests are sometimes called heart damage markers or cardiac enzymes.
The blood test most commonly used to confirm the existence of heart muscle damage is the creatine kinase (KREE'ah-teen KI'nas), or CK for short. A small fraction of the CK enzyme, CK-MB, is often measured as well. CK-MB shows an increase above normal in a person's blood test about six hours after the start of a heart attack. It reaches its peak level in about 18 hours and returns to normal in 24 to 36 hours. The peak level and the return to normal can be delayed in a person who's had a large heart attack, especially if they don't get early and aggressive treatment.
Tests can measure the level of other cardiac muscle proteins called troponins (tro-PO'ninz), specifically troponin T (cTnT) and troponin I (cTnI). These proteins control the interactions between actin and myosin, which contracts or squeezes the heart muscle. Troponins specific to heart muscle have been found, allowing the development of blood tests (assays) that can detect minor heart muscle injury ("microinfarction") not detected by CK-MB. Normally the level of cTnT and cTnI in the blood is very low. It increases substantially within several hours (on average four to six hours) of muscle damage. It peaks at 10 to 24 hours and can be detected for up to 10 to 14 days.
More information about CK enzyme Blood Tests for Rapid Detection of Heart Attack
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