Clin Lab - EKG basics Flashcards
Dimensions for small boxes
1mm x 1mm
Dimensions for big boxes
5x5 small boxes
- 5mm x 5mm
What is measured on the horizontal axis of EKG?
time
Time for 1 small box
0.04 sec (40 ms)
Time for 1 big box
0.2 sec (200 ms)
Time for 5 big boxes
1 sec (1000 ms)
What is measured on the vertical axis of EKG?
voltage (mV)
Voltage for 1 small box
0.1 mV
Voltage for 1 big box
0.5 mV
Voltage for 2 big boxes
1 mV
NOTE
most times we don’t talk about amplitude in terms of actual numbers. It’s more of does it look the way it should.
Which lead is considered the opposite (upside down) of lead II
aVR
Describe visualized of P wave on EKG.
first deflection - smaller, rounded
Describe visualized of QRS complex on EKG.
large deflection
- first (-) wave–> Q wave
- first (+) wave–> R wave
- next (-) wave–> S wave
Describe visualized of T wave on EKG.
last deflection - wider, rounded wave
What is a segment?
a relatively flat (isoelectric) area b/t two deflections
What is an interval?
encompasses at least 1 deflection (+ or -) & 1 flat (isoelectric) segments
P wave represents
atrial depolarization
QRS complex represents
ventricular depolarization
T wave represents
ventricular repolarization
A typical p wave is created by…
an impulse from the SA node
Describe the PR segment
- end of the P wave to start of QRS complex
- all atrial cells are depolarized
- impulse is held by AV node
Describe the PR interval
- start of P wave to start of QRS complex
- time it takes for the impulse to travel through the atria & the AV node
Describe the QRS complex
rapid depolarization through VA bundle, R&L bundle branches, to the terminal ends of the Purkinje fibers throughout the ventricles
- produced ventricular contraction
Are Q waves always present?
No, but can be pathologic in right circumstances
Describe the ST segment
- flat area b/t end of QRS and the beginning of the T wave
- should be same height has PR segment
- all ventricular cell depolarized
What is the J point
point of inflection where the S wave ends & the ST segment begins
Describe the T wave?
- ventricular repolarization
- K+ ions leaving the myocyte returning the cell interior to a (-) charge
- spread out compared to ventricular depolarization - smaller height
Describe the QT interval
- ventricular contraction; beginning of QRS complex to end of T wave
What represents systole on EKG?
QT interval
What represents diastole on EKG?
- end of T wave to begining of QRS complex
Which is long systole or diastole?
diastole
What part of the EKG are electrically silent?
the isoelectric lines
- the flat lines b/t all the waves
What is it called if there is a 2nd (+) wave after the S?
R’ –> RSR’
What is the name of the (+) wave after T wave & before P wave?
U wave
Time: PR interval
120 - 200ms
< 1 big box
Time: QRS complex
60 -100ms
< 3 small boxes
Time: QRS complex gray zone
100 - 120ms
QRS complex: abnormal time
> 120ms
> 3 small boxes
QT interval: time
360 - 440 ms
QT interval varies by & how is this corrected
HR
QTc
QTc value for men & women
< 440ms in men
< 460ms in women
On a 12-lead EKG, how long is each lead?
2.5 secs
How long is a rhythm strip if present?
10 seconds
