When the heart suffers injury or damage such as occurs after a heart attack, it releases certain enzymes into the bloodstream, according to Smart-Heart-Living.com. The blood levels of these enzymes can be measured with simple blood tests. When doctors analyze the blood levels of the enzymes released by the heart and couple this data with the results of other tests such as an electrocardiogram, they can determine whether or not a patient has had a heart attack.
Creatine Kinase (CPK Test)
Creatine phosphokinase, also known as creatine kinase, is an enzyme that occurs principally in the heart, brain and skeletal muscle, according to the University of Maryland Medical Center. The heart muscle will release this enzyme into the blood after it sustains injury or damage such as would occur from a heart attack. If a doctor suspects that a patient has had a heart attack, he will order a blood test to determine the total creatine phosphokinase level. If the total blood level of creatine phosphokinase is above normal, the doctor can conclude that there has been damage to the patients's heart, brain or other muscle tissue. The total blood level of creatine phosphokinase includes various forms of the enzyme. The CK-MB form is specific to the heart, so if the doctor determines that the level of this form is above normal, he can conclude that the patient's heart--and not the brain or other muscle tissue--has been damaged.
Serum Myoglobin Test
According to Medline Plus, the serum myoglobin test determines the level of myoglobin in blood taken from a vein in the patient's hand or arm. Myoglobin is an oxygen-carrying protein found in heart and skeletal muscles. A doctor who thinks that a patient has heart or skeletal muscle damage might order a serum myoglobin test. The normal concentration of myoglobin in blood is zero to 85 ng/ml (nanograms per milliliter). A value greater than the normal concentration may mean that the patient has had a heart attack, or that there is some skeletal muscle injury or inflammation.
Troponins
Troponins are a group of proteins that occur only in heart muscle tissue, and under normal circumstances people do not have any measurable levels of these proteins in their blood, according to HealthCentral.com. About four hours after a person has a heart attack, a simple blood test can detect troponins in the blood, and blood levels will remain high for 10 to 14 days. The more severe the heart attack, the higher the blood levels of the troponins will be. Troponins levels have become one of the most reliable ways for doctors to confirm that a heart attack has occurred and gauge the extent of the damage to the heart muscle.
