PR Interval Duration
Where: Start P-wave to start of Q/R
Time: 0.12 - 0.20 secs (3 to 5 small boxes)
Measures timing between ‘atrial kick to ventricular kick’
QRS Complex Duration
Where: Start Q to end of S
Time: 0.04 - 0.12 secs (1 to 3 small boxes)
A wide QRS is > 3 small boxes
ST-Segment
Where: End of S to the start of T
What: All the ventricular myocardium is depolarized
QT Interval Duration
Time: 0.33 - 0.42 secs
QTc - (QT corrected) normally is < (less than) 0.44 seconds
PR Segment
AV Node holding Action Potential from conducting
Absolute Refractory
Cells do not respond to any stimulus
from the beginning of the QRS complex to the apex of the T wave
Relative Refractory
Cells can respond to LARGER-than-normal stimulus
usually corresponds to the T wave’s downslope
ECG Graph boxes
height means? Width means?
Width (time)
* 1 mm = 0.04 seconds
* 5 mm = 0.20 seconds
Height (amplitude)
* 1mm = 1 mV
* 5 mm = 5 mV
bold text = bold lines
P-Wave
Atrial Depolarization
what makes a Q Wave significant?
- At least 1 small box wide
- > 1/3 height of the QRS complex
- Seen in leads V1-3
This defines a ‘pathologic’ Q (uppercase) wave
T Wave
- Ventricular Repolarization
- Ventricles are turning back to negative charges
ALL wave begins and ends at the ________
Isoelectric Line
Q-Wave Morphology
Q = represents what pathology
Pathologic Q waves are a sign of previous myocardial infarction.
They are the result of the absence of electrical activity.
A myocardial infarction can be thought of as an electrical ‘hole’ as scar tissue is electrically dead and therefore results in pathologic Q waves.
The normal is a lowercase q
Q wave
Ventricular Septal Depolarization
R wave
Resultant or major ventricular muscle depolarization. The resultant vector is directed downward and leftward.
S Wave
Basal Ventricular depolarization
The base of the ventricles connects to the atria.
ST segment
All the ventricular myocardium is depolarized.
