Diagnostic analysis of acute myocardial infarction

"Elevation of cardiac enzymes is the best test for the diagnosis of acute myocardial infarction".


This is a blood test that measures the levels of heart muscle enzymes allowing the diagnosis of acute myocardial infarction.

When, for example, due to the presence of a thrombus in a coronary artery, the heart cells are not properly irrigated, this prevents them from performing their functions and causes them to be injured and subsequently die, which is called acute myocardial infarction (AMI).

There are several protocols for diagnosing and monitoring AMI. As a general rule, AMI is diagnosed if pain is detected at the heart level or alterations in the electrocardiogram and, in addition, there is an elevation of cardiac enzymes in the blood as a result of cell rupture. If these enzymes do not increase, the injury can be considered reversible.

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When is a diagnosis of myocardial infarction made?

In an infarcted patient, an increase in the number of leukocytes and in the rate of globular sedimentation can be detected in the blood, but it is the elevation of cardiac enzymes that is the best test for the diagnosis of acute myocardial infarction (AMI).

The speed at which enzymes appear in the blood depends on certain factors such as their size, location, solubility and blood flow in the infarct area.

Most frequent indications of this test:

  • Angina pectoris.
  • Chest pain.
  • Acute myocardial infarction.

Do you have any of these diseases?

You may need to have a cardiac enzyme test

Types of cardiac enzymes

The enzymes used as diagnostic indicators of AMI are

  • Total creatine phosphokinase (CK or CPK) which regulates the availability of energy in muscle cells.
  • Lactate dehydrogenase (LDH) which intervenes in the anaerobic metabolism of glucose. 
  • Aspartate transaminase (GOT or AST) which is involved in the metabolism of some amino acids.

These enzymes are found not only in the heart but also in other tissues, so it will be necessary to perform serial determinations for 3-4 days to support the diagnosis.

The determination of isoenzymes located mainly in heart cells (such as CK-MB, LDH1 and LDH2) improves the specificity of the tests for the diagnosis of AMI.

There are several phases behind an AMI. There is a slow initial phase in which the enzymes in the blood are within their normal range. It can take up to 6 hours before an elevation in CK-MB can be detected.

After this phase, the enzymes increase rapidly, the values being proportional to the extent of the infarcted area. Proper interpretation of enzyme values in AMI diagnosis depends on obtaining the samples at the right time.

It is recommended to obtain a sample at the time of admission and others at 6, 12 and 24 hours. 

The presence of normal levels of CK-MB, total CK and LDH in properly obtained samples allows to rule out, with a high degree of certainty, the existence of an AMI.

Normally CK-MB represents 3-6% of total CK, after an AMI that value can increase up to 10-20%.
Determining LDH1 and LDH2 isoenzymes is very useful.

Where do we do it?


The Clinical Biochemistry Service
of the Clínica Universidad de Navarra

The Clinical Biochemistry Service of the Clinica Universidad de Navarra is responsible for performing the biochemical analyses requested by the medical specialists of our center.

We carry out technical quality controls to guarantee the proper functioning of the equipment and the highest precision in the results obtained from the samples.

In order to guarantee excellence in patient service, we offer the response with the results of the analyses in the shortest possible time, responding in only 46 minutes in some cases of general analysis.

Organized in care units

  • General biochemistry.
  • Electrolytes.
  • Hormones, urine and proteins.
  • Markers.
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Why at the Clinica?

  • Maximum speed in offering the analytical results.
  • We carry out quality controls to guarantee the correct and most precise results obtained.
  • We work in a multidisciplinary way with all the departments of the Clinic.