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Diagnosis of a Heart Attack

This article is about the diagnosis of a heart attack. In the hospital the Emergency Room physician will assess the patient right away and do appropriate tests like an ECG, blood work for cardiac enzymes, start IV lines and give intravenous fluid. A cardiac monitor is applied to the skin right away as well which tells the physician whether there are any dangerous irregular heartbeats developing.

Cardiac enzymes

Within a short period of time the cardiac enzymes will be reported back to the ER physician and indicate whether or not damage to the heart muscle has occurred. The isoenzyme of creatine kinase, called CK-MB, is found abundantly in heart muscle and is released following a heart attack as early as 3 hours of the onset of a heart attack. It peaks at 24 hours and normalizes at 2 to 3 days. The cardiac specific troponins (Troponin I and T, or abbreviated as TnI and TnT ) are other markers for heart attacks and show up in the blood 3 hours after a heart attack and are lasting until 5 to 7 days.

Myoglobin marker

Another marker for heart attacks is myoglobin. Following a heart attack the heart releases this into the blood over 1 to 2 hours. Myoglobin reaches a peak at 5 to 6 hours and returns to normal within 24 hours. Between these three blood tests (CK-MB, TnI or TnT and myoglobin) virtually all heart attacks can be detected in an acute situation.


A 12 lead ECG tracing identifies those patients who benefit from fibrinolytic therapy (see under “treatment” below).
When in doubt, the cardiologist may want to do a stress test of the heart. This is an exercise test in combination with ECG’s before, during and after the test. This shows whether the oxygen supply to the heart muscle remains constant during exercise or whether it drops off. Here is a link showing an image of a patient doing an exercise stress test.

 Diagnosis Of Heart Attack

Diagnosis Of Heart Attack

If this test is not clearly positive, meaning that there are narrowed coronary arteries proven, this test can be more refined by doing a thallium stress test or the MIBI scan. A myocardial perfusion imaging (MIBI) test is also known as a nuclear stress test. It measures blood flow through the coronary arteries and gives a more complete assessment regarding the presence of cardiovascular disease.

Clinical example

If  a patient has chest pain the physician can order a MIBI scan. If this shows severe perfusion defects at the bottom of the heart, the  cardiologist can offer stents or bypass surgery.  A repeat MIBI scan shows the normalization of the heart perfusion. Chest X rays can detect congestive heart failure and give an overall impression of the heart size. Two-dimensional echocardiography shows whether there are any motion abnormalities of the heart chamber. Also the heart valves can be examined this way. Contractility problems can be depicted, which would tell the cardiologist to look at this patient more carefully, perhaps with a MIBI scan or by doing a heart catheterization.


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More references

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Last modified: March 28, 2022

This outline is only a teaching aid to patients and should stimulate you to ask the right questions when seeing your doctor. However, the responsibility of treatment stays in the hands of your doctor and you.