Some of the abnormalities detected by the ECG are as follows:

1. Defects in the heart.

2. The irregular rhythm of the heart, also known as arrhythmias.

3. Narrowed or obstructed arteries in the heart (coronary artery disease)

4. To check damage to the heart after a heart attack

5. A heart attack in emergencies.

6. Congenital heart defects

7. Abnormal electrolyte balance in the blood (calcium, potassium, magnesium, etc.)

8. Thickened muscles of the heart. This condition is also known as hypertrophy.

9. Harmful effects on the heart from some lung conditions e.g. pulmonary embolus, blood clots to the lungs and emphysema.

10. Harmful effects on the heart from various systemic or heart diseases like thyroid disease or hypertension.

11. Improper blood flow or blood circulation in the heart. This is also known as ischemia.

12. Abnormal cardiac impulse conduction which may be due to metabolic or cardiac diseases.

ECG is also advised if there are any of the following symptoms observed by the doctor:

1. Chest pain

2. Shortness of breath

3. Dizziness

4. Fatigue

5. Very fast heartbeat

There are certain other conditions, wherein the patient has to undergo the ECG. These conditions are as mentioned below:

1. Any family history of heart attack or stroke.
2. Any past personal history of a heart attack or severe chest pain.
3. Any scheduled surgical procedure of the heart, which may need an ECG, in order to check the condition of the heart before the surgery.
4. In order to check the effectiveness of medicines given to improve the condition of the heart.
5. To monitor the effective working of an electrical device known as a pacemaker (artificial heart).