The ECG is a diagnostic machine use to measure and record the electric activity of the heart with minute details. Doctors see and interpret these outputs from the ECG machine to diagnose the condition of the heart.
An Overview of the ECG Machine. The ECG was developed by the scientist named Willem Einthoven in 1893, who was also awarded the Nobel Prize for his contribution. The standard ECG is 12-lead ECG that is used throughout the world. It measures the heart activity from 12 points of view.
ECG readings are obtained by connecting electrodes in the body. At about 12 points on the body, metal electrodes are connected. There are useful medical videos which very clearly provide this information. The technician connects the chest, back, hands and legs to these electrodes so that the rhythm of the heart can be monitored. The readings appear on the screen in about five to ten minutes.
The electrocardiogram is a method to read the health of the heart. The heart is responsible for the flow of blood throughout the body and it accomplishes this by its "pumping activity".
When there is an irregularity in the functioning of the heart, the individual may face problems due to irregular flow of blood. Hence, ECG readingsmay be taken to interpret the electrical signals generated by the heart.People over the age of forty or so, who lead a stressful life or have been experiencing pain in the chest, or dizziness, should get an Electro Cardio Graph scanning done as soon as possible, in order to reveal the nature of the abnormality. E.g. in case of heart attack, the portion of the heart affected will be electrically silent and will be shown as a change in the voltage in the ECG.
For Beginning Nursing Students Or, perhaps you are a nursing technician who is reading the ECG printouts in your daily job testing patient monitors with ECG simulators. You will find here a simple explanation of the basic ECG patterns which will constitute a baseline with which all the more complicated arrhytmic heart patterns will be compared.
Basic ECG Interpretation
First, consider the flow of blood through the heart sections
For the purpose of the explanation of the cardiogram, let's first establish the naming: Atrium is the upper part of the heart, Ventricle is the lower, bigger part of the heart. Between them, there is a heart valve which is designed to open in the direction of the blood flow. The blood always flows in the direction from the atrium to the ventricle. The valve design prevents the blood from flowing in the opposite direction.
The flow of electric impulses follows the flow of blood
The electric impulses that regulate the contractions of the heart have their own pathway from their origin in the "sinus" section of the top of the wall of the atrium. Starting in the atrium, the initial signal will cause the contraction of the atrium. From there, the electric signal lines go through the dividing region between the atrium and the ventricle (the AV region), where the signals get significantly delayed in time. Then, they move through the walls of ventricle where they finally cause the contraction of the ventricle.
The ECG signal mimics the flow of the electric impulse through the walls of the heart
The normal ECG signal is composed of the phases P, QRS, and T. The ECG signal in time follows the electric signal passing from the "sinus" section of the atrium, through the atrium, the AV section, and finally to the ventricle. So, the sequence of the repeating pulses you will see in the electrocardiogram printout will be as follows:
- P phase which takes about 0.1s is a small pulse representing atrial depolarization which is associated with atrium contraction. After a delay, the next phase is
- QRS complex phase take about 0.1s is a large pulse representing ventricular depolarization which is associated with ventricular contraction. The phases Q and S are actually slightly negative, while the phase R is strong and positive. Incidentally, as the valve closes, the atrial repolarization takes place which is associated with atrium expansion. This, however, is hidden due to the size of the ventricular depolarization signal. Finally, the last phase is
- T phase which represents ventricular repolarization, corresponding to the slower expansion of the ventricle.
