EKG or electrocardiography is the recording of the graphics of electrical potential variations caused by the heart's muscular electrical activity and detected on the surface of the body. EKG's work principles are recording electrical signals related to the heart's activity and resulting a graph of recorded voltages to time.
EKG is a method to learn the performance of cardiac muscles that it may support the diagnosis of the heart's abnormality and the heart's functionality tendency or change.
Electrocardiograph is a tool to perform electrocardiography, while electrocardiogram is the paper on which the graphic of electrical potential variations due to cardiac muscles excitation detected on the surface of the body are recorded.
Normal electrocardiogram suggests the deflection resulted by atrial and ventricular activities as the change of voltage and polarity (positive and negative) tendencies to time. The first deflection or P wave is the result of atrial excitation QRS complex deflection is the result of ventricular excitation (depolarization) T wave is the result of ventricular recovery (repolarization).
Critical factors affecting EKG test are:
- Incorrect placing of electrode or electrode's not being firmly attached to the skin may affect the accuracy of EKG record.
- The temperature around the test area must be maintained in the range of 20-25oC and the humidity must be low.
- EKG test must be performed away from tools producing noise such as equipments of ultrasonography, X-ray, mobile phone or other electrical tools.
- The patient must be calm, unmoved and quiet during the test. The patient's legs and arms are ascertained not to be in contact with any metal.
- The data of patient's age and sex have to be correct since several kinds of EKG tools interpret the result under the consideration of age and sex.
- Put away any stuff containing metal such as watch, mobile phone, key, etc.
- The patient is not allowed to do exercise preceding the test.