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How can lab tests show whether I'm having a heart attack?

Dr. Chetan A. Patel, MD
Cardiologist (Heart Specialist)

There are particular lab tests that can detect heart attacks. The most commonly used test currently is a cardiac specific troponin level. This test is very sensitive and specific for detecting heart damage including a heart attack. Cardiac troponin is a protein found in heart muscle that is involved in muscle contraction. It is released into the blood stream when heart muscle is damaged. It is important to remember that there can be delay of hours before troponin is detected in the blood after heart damage so often the test needs to be repeated over several hours.

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A damaged heart can leak enzymes, which shows up in blood tests, thus indicating a heart attack.

To confirm whether or not a patient has had a heart attack (or myocardial infarction), a doctor generally requires an EKG and/or blood tests.

Certain blood tests read as "abnormal" after a heart attack has occurred. When heart muscle cells die, chemicals in these cells are released into the blood. The release of these chemicals does not occur instantly and usually takes several hours. A doctor, therefore, cannot always tell you on the spot if you are having a heart attack. Because results take time to develop, the doctor may admit you to the hospital to have a series of tests including EKGs and blood tests to catch any abnormalities as they happen so he can determine if a heart attack has occurred.

The chemicals from heart muscle cells are called markers of myocardial infarction and include CPK, CPK-MB, Troponin and Myoglobin. Some markers occur in other cells and can be limited in usefulness when diagnosing a heart attack.

  • The CPK marker begins to rise four to eight hours after the onset of a heart attack. It can be detected for 48 to 72 hours and is found in the heart, brain and skeletal muscles.
  • The CPK-MB marker begins after three to four hours, peaks at 12 to 24 hours and can be detected up to 48 hours. This marker is found in the heart.
  • The Myoglobin marker begins after one to two hours, peaks after four to six hours and can last up to 24 hours. It is found in the heart and skeletal muscles.
  • The Troponin marker begins after three to six hours, peaks in 12 to 24 hours and can be detected for up to a week. It is found in the heart and skeletal muscles.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.