Flashcards in ECG Deck (21)
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1
Electrical activity causes...
Mechanical activity SO electrical activity happens first
2
2 speeds
50mm/sec
1mm=0.02 sec
25mm/sec
1mm=0.04sec
1 or the other
3
Leads
Monitoring heart at different angles
Each different angle/pair of electrodes = LEAD
Each lead = + & - electrode
3 lead systems
4
How to place leads
Place patient in right lateral recumbancy = put on right side
Attach electrodes to skin proximal to elbows and stifles
Wet electrodes with alcohol
Check speed, amplitude and other setting and calibration
Attach negative electrode to one limb and positive to the other limb
5
3 bipolar Bipolar limb heads
Measure current from negative to positive electrode
Measuring same electrical activity but from different angles
Lead I = RA to LA
Lead II = RA to LL
Lead III = LA to LL
Grounding Lead = RL
6
Unipolar Limb Leads
Same leads at bipolar limb leads
3 new angles
Lead aVR = + on RA
Lead aVL = + on LA
Lead aVF = + on LL
7
Chest leads...
Record electrical activity from dorsal and ventral surface of the heart
RA, LA, and LL are connected to form a 0 reference at the center of the heart
ECG records voltage from heart to selected electrode on chest
8
Axis of leads
Direction (degree) from negative to positive
9
Einthoven's Triangle
Tells you direction of the bipolar leads
10
Axis of Leads
- to +
Lead I = 0 degrees b/c horizontal impulse
Lead II = 60 degrees
Lead III = 120 degrees
Lead aVR = 210 or -150
Lead aVL = -30
Lead aVF = 90
11
Why are some waves positive and others negative?
D
12
Reading ECG
Impulses toward + electrode = upward deflection on ECG
Impulses from - electrode = downward deflection
Impulse traveling perpendicular to lead = ISOELECTRIC TRACING = electrical forces are equal
no electrical activity = BASELINE TRACING = tissue is fully depolarized or repolarized
13
P Wave
QRS Wave
T Wave
Atrial Dep
Ventricular Dep
Ventricular Rep
14
P wave
Atrial Depolarization
SA Node to atria = impulse that is downward and to the left
Upward + deflection in Lead I (horizontal to the left) and Lead aVF (vertical downward)
15
After P wave
Baseline Tracing bc atria dep and ventricals are still rep as impulse moves through AV node
16
QRS Wave
Ventricular Depolarization
wave goes in 3 diff direction bc amount of tissue depolarizing changes as electrical impulse moves through the heart
Septal Dep
Apical Dep
Late Ventrical Dep
17
Septum Depolarization
Right and Downward
Small downward deflection in Lead I (Q wave) and positive deflection in Lead aVF (R wave)
not a lot of current bc not a lot of tissue
18
Apical Depolarization
apical ventricular myocardium
Downward and to the left
Large positive upward deflection (R wave) in Lead I
extend R wave in lead aVF
19
Late Ventricular Depolarization
Upward and to the left
Extends r wave in Lead I
downward deflection in Lead aVF (S wave)
20
ST Segment
End of S wave to the beginning of T wave
when vents completely dep = no current bc atria rep and vent dep
21
