If you are admitted to hospital with a suspected heart attack you will have a blood test to look at the levels of 'cardiac enzymes' in your blood.
Cardiac enzyme tests can tell whether or not you have had a heart attack. Enzymes are proteins that help with chemical reactions in the body. When the heart muscles are damaged, as with a heart attack, the body releases enzymes into the blood. The amount of enzymes released into the blood depends on the amount of damage to the heart.
The levels of cardiac enzymes are measured by taking a series of blood samples over a few days. The levels of enzymes rise shortly after a heart attack and peak between 12 and 24 hours after a heart attack and can stay raised for some time afterward.
Another test measures the levels of 'troponin' in the blood. Troponin is another type of protein and the levels of troponin in the blood shows how much damage there has been to the heart muscle after a heart attack.