Purpose of ECG / EKG (Electrocardiogram)

The electrocardiogram (ECG or EKG) is a noninvasive routine examination of the electrical activity of the heart that is used to reflect underlying heart conditions. Regular heart movements are controlled by a complex set of electrical impulses that direct the upper and lower heart chambers to contract and relax rhythmically. When these electrical activities are interrupted or misguided, the arrhythmia can be symptoms of heart diseases. Furthermore, the impulses can also show signs of structural or metabolic changes like enlargement or hypoxia of cardiac muscle.

A human heart consists of four main components and they all are subjected to diseases.

• Heart valves: regulate the direction of blood flow
• Heart muscle: gives structure to the entire heart and divides the heart into four chambers
• Electrical system: controls and synchronizes the movements of heart muscles
• Coronary arteries: carries blood, nutrient and oxygen to heart tissues

The ECG can tell a lot about the heart's electrical system; however it may or may not say much about the other components of the heart, nor tell the cause of an abnormal condition (e.g. high blood pressure). It is common for someone with normal ECG and yet has critical heart disease. Also many health individuals have abnormal ECG readings and more testing is required to draw any conclusions. Despite its shortcomings, it is still the best screening tool available.

A comprehensive EKG test is normally performed in a medical facility. Electrodes are attached to the subject's four extremities and to six locations on the front of the chest. The electrodes are attached by small suction cups, adhesive patches or Velcro strips. The test lasts for 5 to 10 minutes. The data is recorded and displayed on the ECG machine and is saved in a computer. A stress EKG test is when measurements are taken when the subject is exercising until a target heart rate is achieved. A stress test would have a higher probably of identifying issues with the heart.

The following diagram shows a normal EKG:

By analyzing the pattern and frequency of the ECG recorded, the following information can be extracted :

1. Heart rate
2. Heart rhythm
3. Conduction abnormalities
4. Heart orientation in the chest cavity
5. Evidence of increased thickness of heart muscle (hypertrophy)
6. Evidence of damaged heart muscle
7. Acutely impaired blood flow to heart muscle
8. Warning signs of abnormal cardiac rhythm disturbances

Based on these observations, ECG will help to screen and diagnose for the following conditions :

1. Fast or irregular heart rhythms
2. Abnormally slow heart rhythms
3. Abnormal conduction of cardiac electrical impulses, which are symptoms for cardiac or metabolic disorders
4. Prior heart attacks (myocardial infarction)
5. Reduced blood flow during heart attack (unstable angina)
6. Damage to heart from other heart or systemic diseases, such as high blood pressure, thyroid...
7. Damage to heart from certain lung conditions, such as emphysema, blood clots to lung...
8. Enlarged cardiac chambers (cardiac dilatation)
9. Evidence of abnormal blood electrolytes - calcium, magnesium, potassium
10. Inflammation of the heart (myocarditis) or its lining (pericarditis)
11. Cardiomyopathy - a range of conditions in which the heart muscle (myocardium) does not function normally, including several congenital forms of cardiomyopathies