Electrocardiography (ECG)

The first test performed when you present with chest pain is an ECG. You may be experiencing a heart attack, and an ECG can quickly reveal this. During an acute heart attack (myocardial infarction), characteristic ECG changes such as ST-segment elevation appear, indicating the need for urgent intervention.

If the ECG is normal, your chest pain may be due to non-cardiac causes such as reflux, muscle pain, or anxiety. However, sometimes the ECG may appear normal during pain-free periods, so repeated ECGs or further tests may be required if symptoms persist.

If you feel that your heart is beating fast, slow, or irregularly, an ECG can identify the type of rhythm disturbance. Many arrhythmias such as atrial fibrillation, ventricular tachycardia, and premature beats can be detected on ECG. However, since ECG only reflects a brief 10–15 second snapshot, intermittent rhythm disorders may require rhythm Holter monitoring.

Ideally, an ECG should be recorded during palpitations to capture the abnormal rhythm. If the palpitations have already subsided, the ECG may appear normal.

Even in the absence of symptoms, routine ECG screening is recommended for individuals over the age of 40. If there is a family history of early heart disease or risk factors such as diabetes or hypertension, regular ECG monitoring is especially important. Some heart diseases progress silently and may be detected on ECG before symptoms develop.

ECG is also routinely performed before starting sports activities and prior to surgical procedures.

In patients who have suffered a heart attack, regular ECG follow-up is performed during recovery. ECG changes indicate which regions of the heart muscle were affected and help monitor the healing process. ECGs may be recorded daily in the acute phase, then weekly or monthly afterward.

Permanent ECG findings such as pathological Q waves may indicate a previous heart attack.

Some medications—particularly antiarrhythmic drugs, certain antibiotics, and psychiatric medications—can affect the heart’s electrical activity and lead to dangerous rhythm disturbances. Regular ECG monitoring is recommended when using these medications. Prolongation of the QT interval, in particular, increases the risk of life-threatening arrhythmias.

Some chemotherapy drugs may also have cardiotoxic effects and cause ECG changes.

Blood levels of minerals such as potassium, calcium, and magnesium directly affect the heart’s electrical activity. Abnormally high or low potassium levels, in particular, cause characteristic ECG changes. Patients with kidney disease, severe vomiting or diarrhea, or those using diuretics are at higher risk of electrolyte imbalance.

The ECG helps determine whether these imbalances are affecting the heart and whether urgent treatment is required.

In patients with pacemakers or implantable cardioverter-defibrillators (ICDs), ECG is used to assess whether the device is functioning properly. Pacemaker signals appear as small spikes on the ECG. The presence of these spikes followed by heart contraction indicates proper device function.

ECG is routinely performed during device follow-up visits, and device settings are optimized accordingly.