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Stages of Normal ECG Pattern, "Cardiology Teaching Package." The…
Stages of Normal ECG Pattern
P Wave
Depolarization of the Atrium
AV valves are opened; semilunar valves are closed to prevent backflow
70% of the blood in the atria falls through (gravity helps) mainly by suction from the expanding ventricles
The atria contract
QRS Complex
Q Wave
Depolarization of the septum
The septum begins to depolarize, left to right
A small, negative wave
R Wave
The electrical signal is now passed through the main portion of the ventricular walls
With the ventricle walls being thick, they require much energy; thus, more voltage required
S Wave
Another small, negative wave
The Purkinje fibers are depolarized
Before this, there is a 'pause' where stimulus is delayed, allowing for blood to fill the ventricles
Increasing pressure closes the AV valves
When the valves close, the electrical stimulus is passed to the bundle branches and Purkinje fibers
The ventricles are contracted
Atria are relaxed
Blood is ejected from the heart, as the heart is in ventricular systole
T Wave
Both ventricles repolarize
Ventricular relaxation
ST Segment
Between the S and T wave where there is no conduction
Indicator for myocardial ischemia or necrosis, if conduction is noted here
"Cardiology Teaching Package." The University of Nottingham. Retrieved November 19, 2020, from
https://www.nottingham.ac.uk/nursing/practice/resources/cardiology/function/sinus_rythm.php