ECG

Question 1

Electrical activity causes…

Answer 1

Mechanical activity SO electrical activity happens first

Question 2

2 speeds

Answer 2

50mm/sec
1mm=0.02 sec

25mm/sec
1mm=0.04sec

1 or the other

Question 3

Leads

Answer 3

Monitoring heart at different angles

Each different angle/pair of electrodes = LEAD

Each lead = + & - electrode

3 lead systems

Question 4

How to place leads

Answer 4

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

Question 5

3 bipolar Bipolar limb heads

Answer 5

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

Question 6

Unipolar Limb Leads

Answer 6

Same leads at bipolar limb leads
3 new angles

Lead aVR = + on RA
Lead aVL = + on LA
Lead aVF = + on LL

Question 7

Chest leads…

Answer 7

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

Question 8

Axis of leads

Answer 8

Direction (degree) from negative to positive

Question 9

Einthoven’s Triangle

Answer 9

Tells you direction of the bipolar leads

Question 10

Axis of Leads

Answer 10

• 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

Question 11

Why are some waves positive and others negative?

Answer 11

D

Question 12

Reading ECG

Answer 12

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

Question 13

P Wave
QRS Wave
T Wave

Answer 13

Atrial Dep
Ventricular Dep
Ventricular Rep

Question 14

P wave

Answer 14

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)

Question 15

After P wave

Answer 15

Baseline Tracing bc atria dep and ventricals are still rep as impulse moves through AV node

Question 16

QRS Wave

Answer 16

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

Question 17

Septum Depolarization

Answer 17

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

Question 18

Apical Depolarization

Answer 18

apical ventricular myocardium

Downward and to the left

Large positive upward deflection (R wave) in Lead I
extend R wave in lead aVF

Question 19

Late Ventricular Depolarization

Answer 19

Upward and to the left

Extends r wave in Lead I
downward deflection in Lead aVF (S wave)

Question 20

ST Segment

Answer 20

End of S wave to the beginning of T wave

when vents completely dep = no current bc atria rep and vent dep

Question 21

Ventricualr depolarization

Answer 21

Cells rep based on length of action potential

Epicardium rep first and creates a current in the same direction as dep
Endocardium rep after

T wave in same direction as major wave of QRS

Pos in Lead I