The rest electrocardiogram is a simple test. It does not require any particular preparation, it is non-invasive, painless and risk-free (it doesn’t have contra-indications, contrary to the stress electrocardiogram test that is not recommended for people who suffer of cardiac failures). 10 electrodes are placed on the patient's limbs and on the surface of the chest. The overall magnitude of the heart's electrical potential is then measured from twelve different angles ("leads") and is recorded over a period of time (usually ten seconds).

The overall time required by this test is a few minutes.

The medical report includes:

• The P-wave represents the atrial activation (depolarization) that, being generated by a relatively small portion of myocardium, results in a small voltage.
• The P-Q interval (or P-R) corresponds to an atrioventricular pause.
• The QRS complex (or rapid complex) corresponds to the diffusion of the stimulus in the ventricles.
• The Q wave represents the depolarization in correspondence of the first portion of the intraventricular septum. As the portion of the myocardium is small, the voltage is also small.
• The R wave represents the principal expansion of the depolarization inside of the heart and of its base towards the surface and towards the end of the ventricles. As it concerns a large portion of the heart’s muscular mass it creates relatively large voltages and implies a significant derivation of the electric curve upwards.
• It follows an “isoelectric” stretch (ST stretch) that represents a momentary state of electric balance in the cardiac walls. It comes before the T wave determined by the repolarization of the myocardium after that the systole (contraction) is completed. This period of the cardiac process is relatively slow so an extended and rounded curve is obtained.

It is the test where the electric variations that happen during the cardiac activity are evaluated. It is required to determine if the heart is suffering and if the cardiac rhythm is regular or not.

The report identifies:

• Cardiac frequency.
• The presence of disturbances or irregularity of the cardiac rhythm.
• The presence of an enlarged heart- (all or in part).
• The presence of electrolytic instabilities that are alterations of the concentration of ions as sodium and potassium in the blood.

Sometimes the basal electrocardiogram is not sufficient enough to formulate a diagnosis of a heart disease. Symptoms may not be present or visible during the electrocardiogram to confirm or exclude a diagnosis of a cardiac pathology.

Vice versa, in the absence of a symptom, a negative registration can highlight a situation of false normality even in the presence of cardiopathy. The particular forms (morphologies) of the electric stimulus recorded (electrocardiographic track) permit to determine with precision the type of rhythm of the heart at that moment, the modality of propagation of the stimulus that, along the conduction plot, it branches off from the base to the cliff of the heart.