An electrocardiogram, also called EKG or ECG, is a measurement of the electrical activity of your heart. This is a non-invasive test that measures the electrical signals through small electrodes that are placed at various places on your skin.
An EKG test is the best way to measure abnormal heart rhythms.
EKG and the heart’s electrical system
Your heart beats because of special cells that make electricity. They produce electrical impulses in natural pacemaker cells, which spread over the heart, causing it to contract.
Your heart’s natural pacemaker is called the sinoatrial node, or SA node. Your heart also has special fibers that carry the electrical signals from the SA node to the rest of the heart.
Although any electrical tissue in the heart can generate an electrical impulse and act as a pacemaker, the SA node does it fastest and is normally in control. If the SA node fails, other parts of the electrical system can take over, usually at a slower rate.
While pacemaker cells create the electrical impulse that causes the heart to beat, the autonomic nervous system (ANS) can change the pulse rate and strength of the heart’s contractions. The ANS includes the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nerves increase the heart rate and increase the force of contraction. The parasympathetic nerves do the opposite. All this activity produces electrical waves we can measure. The measurement is typically represented as a graph called an electrocardiogram. Your electrocardiogram shows your heart’s electrical activity, labeling three phases:
- P wave coincides with the spread of electrical activity over the atria and the beginning of its contraction.
- QRS complex coincides with the spread of electrical activity over the ventricles and the beginning of its contraction.
- T wave coincides with the recovery phase of the ventricles.
Why is electrocardiogram abbreviated EKG?
People often wonder why electrocardiogram is abbreviated as EKG instead of ECG. The reason is that ECG sounds very similar to EEG, which is the abbreviation for electroencephalogram, a test that measures electrical activity in the brain. In order to avoid confusion, it became a convention to use the abbreviation for the German spelling—elektrokardiogramm—for the heart test, which is why it is commonly called an EKG.
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