12 lead ECG interpretation

Question 1

Locations on body:
Lead I

Lead II

Lead III

Answer 1

Lead I = + on left and - on right arm

Lead II = + on left leg and - on right arm

Lead III = + on left leg and - on left arm

Question 2

Locations on body
aVR

aVL

aVF

Answer 2

aVR = right arm

aVL = left arm

aVF = left leg

Question 3

Septal infarcts are most evident in which leads

Answer 3

V1 and V2

Question 4

___ is the dominant producer of voltage in heart

Answer 4

left ventricle

Question 5

QRS axis points ____ and ____

Answer 5

QRS axis points left and posterior

Question 6

normal depolarization goes in which direction

Answer 6

down from right arm to left leg

Question 7

which leads appear + and which leads are -

Answer 7

+ = I, II

• = V1, V2, aVR

Question 8

normal QRS axis ranges from ___ to ___

Answer 8

-30 to 90

Question 9

what is LAD angles?

Answer 9

-30 to -90

LAD ALWAYS ABNORMAL

Question 10

what is RAD angles

Answer 10

+90 to +180

CAN ALSO BE FOUND IN CHILDREN/CHEST MALFORMATION

Question 11

RAD is negative in which lead

LAD is negative in which lead

Answer 11

RAD = neg at lead I, pos at lead II

LAD = pos at lead I, neg at lead II

Question 12

thumbs up rule

Answer 12

which ever thumb is positive is the axis
both positive = normal axis

both negative = indeterminate

Question 13

what does RBBB or LBBB or ectopic ventricular beat appear on ecg in common

Answer 13

widened QRS

Question 14

RBBB shows as what on ecg

Answer 14

late R in V1 + T wave inversion in V1

large S in V6/I

Question 15

LBBB shows as what on ecg

Answer 15

no R and large S in V1

late R in V6/1 + T wave inversion in V6

Question 16

Hemiblocks cause ____ without widening the QRS

Answer 16

axis shifts

Question 17

Hemiblocks cause axis shifts without ____

Answer 17

widening the QRS

Question 18

___ causes LAD

Answer 18

blocks in anterior fascicle

Question 19

____ causes RAD

Answer 19

blocks in posterior fascicle

Question 20

What possibilies if P wave abnormalities

Answer 20

1) Tall P (>2.5 mm in inferior lead = R atrial enlargement)

2) Wide notch P wave with late negativity in V1 (L atrial enlargement)

Question 21

what possibilities if QRS wide?

Answer 21

(>0.12 sec = BBB)
RBBB = large late R’ in V1 + late S wave in V6

LBBB = wide QS in V1 + wide R wave in V6

Question 22

what possibilities if axis shift

Answer 22

Right axis = RVH or posterior hemiblock

Left axis = LVH or anteiror hemiblock

Question 23

what possibilities if high voltage

Answer 23

ventricular hypertrophy

RVH (R wave in V1 + S wave in V6 > 11mm)

LVH (S wave in V1 + R wave in V6 > 35) + T wave inversion

Question 24

what possibilities if Q waves

Answer 24

infarct if in 2 related leads
(25% of R wave or 0.04 sec wide)

2 contiguous leads = necrosis

Question 25

what possibilities if ST elev?

Answer 25

injury if local

pericarditis if diffuse

Question 26

what possibilities if ST depression?

Answer 26

ischemia

subendocardial infarct

reciprocal signs from MI (with ST elev or old MI)

Question 27

what possibilities if T inversion?

Answer 27

ischemia (early MI)

hypertrophy

BBB

Question 28

what possibilities if Long QT

Answer 28

electrolyte imbalance (low K, Ca2+, Mg2+

type 1A/C, type 3, congenital long QT)

Question 29

late R in V1 + T wave inversion in V1

large S in V6/I

Answer 29

RBBB

Question 30

no R and large S in V1

late R in V6/1 + T wave inversion in V6

Answer 30

LBBB

Question 31

which BBB masks MI

Answer 31

LBBB

Question 32

QRS is wide, think ___

Answer 32

BBB

Question 33

QRS is narrow, think ___

Answer 33

hypertrophy