The most important procedure to obtain certainty in case of a suspected myocardial infarction is the electrocardiogram or ECG for short. This involves measuring the excitation of the heart muscles using electrodes. There are typical changes in the ECG that characterize a myocardial infarction.
After the acute stage, further circulatory disorders or chronic cardiac arrhythmia are detected by means of a stress ECG and a long-term ECG. The ECG depicts the electrical excitation in the heart, which is, so to speak, the pacemaker for the beating of the heart. Depending on which cells are excited and thus activated, rashes occur in the ECG.
The time in which all cells in the heart chambers are activated is visible in the ECG as a so-called ST segment. As heart muscle cells die in the event of a heart attack and can therefore no longer be activated, a change occurs which is shown in an ST segment elevation, i.e. a higher line deflection than is usually seen in the ECG. This can be detected immediately after the heart attack has occurred and the various points at which the electrical excitation on the body is measured can provide information about the location of the infarction on the heart.
A QRS change indicates tissue that has already died, i.e. tissue that has already died as a result of a lack of blood flow. Such a change always remains visible as a so-called infarction scar. In the acute stage of myocardial infarction, the ECG can also make accompanying complications such as cardiac arrhythmia or ventricular fibrillation visible. However, in about 20% of infarction patients, no typical signs are visible on the ECG and the infarction must be detected by means of a blood sample.
If an infarction is suspected, imaging procedures such as angiography or echocardiography also show signs of an infarction. Thus, tears in the chamber wall, inability to close the mitral valve or fluid in the pericardium (pericardial effusion) can be detected. Angiography allows the direct detection of occlusions and constrictions by means of a cardiac catheter.
Finally, a laboratory examination also reveals signs of a myocardial infarction. The following circumstance is taken advantage of: Dying heart muscle cells, which are typical for a myocardial infarction, secrete a so-called biomarker. A biomarker can be an enzyme or another protein.
These biomarkers of the heart include One measures the concentration of these markers in the blood over a period of time. A very high concentration can be a sign of a heart attack. In this way, conclusions can be drawn about the beginning, intensity and end of a heart attack, which can later become important for precise diagnosis and therapy.
- Creatine kinase
- Lactate dehydrogenase
- Aspartate aminotransferase
Depending on their function, the various cells of the body contain different proteins. For example, the protein troponin is only present in the heart muscle cells. In the case of a heart attack, heart muscle cells die due to a disturbed blood circulation.
As a result, the proteins from inside the cell, including troponin, are released and are present in increased amounts in the blood. From two hours after the onset of the heart attack, an elevated troponin level in the blood can be detected. This is reliable evidence for the diagnosis of a heart attack and can be detected by means of a quick test with blood drops or by a blood test in the laboratory.