Electrocardiography (ECG) records the electrical impulses generated from the heart muscles and provides a graphic illustration of the summation of these impulses and their sequence and magnitude.
The P wave represents the electric activity associated with the sino-atrial node and the spread of the impulse over the atria.
It is a wave of depolarization.
The QRS complex (wave) is actually composed of three separate waves: the Q wave, the R wave, and the S wave.
They are all caused by currents generated when the ventricles depolarize before their contraction.
Because ventricular depolarization requires septal and right and left ventricular depolarization, the electrical wave depicting these events is more complex than the smooth P wave.
The P-R interval is measured from the beginning of the P wave to the beginning of the QRS complex.
It is termed P-R instead of PQ because frequently the Q wave is absent.
This interval represents the time that elapses from the beginning Q-T interval of atrial depolarization to the beginning of ventricular depolarization.
The T wave represents repolarization of the ventricles.
The Q-T interval begins with the QRS complex and ends with the completions of the T wave.
It represents ventricular depolarization and repolarization.
This interval varies with the heart rate.
the faster the rate, the shorter the Q-T interval.
Therefore in children this interval is normally shorter than in adults.
The S-T segment is normally an isoelectric (flat) line that connects the end of the S wave to the beginning of the T wave.
The T-P interval represents atrial and ventricular polarization in anticipation of the next cardiac cycle.
An electrocardiogram is taken by placing leads or electrodes on the skin to transmit electric impulses back to a recording machine.
By means of telemetry the pattern of electrical impulses can be demonstrated on an oscilloscope.
The position of the electrodes on the body and the manner in which they are attached to the electrocardiogram machine influence the type of recording.
Usually the electrodes are attached to the body with a rubber strap or a type of adhesive (for continuous monitoring).
An electrolyte lubricant or electrolyte-soaked gauze is placed between the skin and lead to increase conductivity.
The PQRST complex is plotted on graph paper.
Each small block represents 0.
004 second horizontally and 1mv (millivolt) vertically.
By counting the number of squares intersected by the complex, one can calculate the various intervals, such as the P-R or Q-T interval and the amplitude (height) of each wave.
Other information supplied by electrocardiogram includes heart rate, rhythm, abnormalities; of conduction, muscular damage (ischemia), hypertrophy, effects of electrolyte imbalance, influence of various drugs, and pericardial disease.
However, the electrocardiogram gives no direct information concerning the mechanical performance of the heart as a pump.
The P wave represents the electric activity associated with the sino-atrial node and the spread of the impulse over the atria.
It is a wave of depolarization.
The QRS complex (wave) is actually composed of three separate waves: the Q wave, the R wave, and the S wave.
They are all caused by currents generated when the ventricles depolarize before their contraction.
Because ventricular depolarization requires septal and right and left ventricular depolarization, the electrical wave depicting these events is more complex than the smooth P wave.
The P-R interval is measured from the beginning of the P wave to the beginning of the QRS complex.
It is termed P-R instead of PQ because frequently the Q wave is absent.
This interval represents the time that elapses from the beginning Q-T interval of atrial depolarization to the beginning of ventricular depolarization.
The T wave represents repolarization of the ventricles.
The Q-T interval begins with the QRS complex and ends with the completions of the T wave.
It represents ventricular depolarization and repolarization.
This interval varies with the heart rate.
the faster the rate, the shorter the Q-T interval.
Therefore in children this interval is normally shorter than in adults.
The S-T segment is normally an isoelectric (flat) line that connects the end of the S wave to the beginning of the T wave.
The T-P interval represents atrial and ventricular polarization in anticipation of the next cardiac cycle.
An electrocardiogram is taken by placing leads or electrodes on the skin to transmit electric impulses back to a recording machine.
By means of telemetry the pattern of electrical impulses can be demonstrated on an oscilloscope.
The position of the electrodes on the body and the manner in which they are attached to the electrocardiogram machine influence the type of recording.
Usually the electrodes are attached to the body with a rubber strap or a type of adhesive (for continuous monitoring).
An electrolyte lubricant or electrolyte-soaked gauze is placed between the skin and lead to increase conductivity.
The PQRST complex is plotted on graph paper.
Each small block represents 0.
004 second horizontally and 1mv (millivolt) vertically.
By counting the number of squares intersected by the complex, one can calculate the various intervals, such as the P-R or Q-T interval and the amplitude (height) of each wave.
Other information supplied by electrocardiogram includes heart rate, rhythm, abnormalities; of conduction, muscular damage (ischemia), hypertrophy, effects of electrolyte imbalance, influence of various drugs, and pericardial disease.
However, the electrocardiogram gives no direct information concerning the mechanical performance of the heart as a pump.
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