Electrocardiogram

Question 1

what results in positive deflection

Answer 1

the electrical impulse travelling towards the electrode

Question 2

what results in negative deflection

Answer 2

the electrical impulse travelling away from the electrode

Question 3

6 chest electrodes

Answer 3

v1-6 or c1-6

Question 4

right arm electrode

Answer 4

red

Question 5

left arm electrode

Answer 5

yellow

Question 6

left leg electrode

Answer 6

green

Question 7

right leg electrode

Answer 7

black - neutral/dummy

Question 8

types of coronal leads (limb leads)

Answer 8

bipolar leads - 1, 2, 3
unipolar leads - aVL, aVR, aVF

Question 9

the qrs axis

Answer 9

represents the net overall direction of the hearts electrical activity

defined as ranging from -30 to +90 degrees

Question 10

what can abnormalities in the qrs axis hint at

Answer 10

ventricular/structural abnormality
conduction abnormality

Question 11

left axis deviation

Answer 11

-30 to -90

Question 12

right axis deviation

Answer 12

+90 to +180

Question 13

3 waves produced during cardiac cycle

Answer 13

p wave
qrs complex
t wave

Question 14

p wave

Answer 14

caused by atrial depolarisation

Question 15

qrs complex

Answer 15

caused by ventricular depolarisation

Question 16

t wave

Answer 16

from ventricular repolarisation

Question 17

pr interval

Answer 17

time to conduct through av node/bundle of His

Question 18

qrs duration

Answer 18

time for ventricular depolarisation

Question 19

st segment

Answer 19

start of ventricular repolarisation

Question 20

st elevation

Answer 20

acute infarction

Question 21

st depression

Answer 21

ischaemia
LV strain

Question 22

woldd-parkinson-white ecg

Answer 22

a to v conduction through accessory pathway on rest ecg
delta wave with short pr interval

Question 23

when is there a risk of ventricular fibrillation

Answer 23

if patient develops atrial fibrillation and if accessory pathway is capable of rapid conduction

Question 24

left ventricular hypertrophy

Answer 24

r wave in v5 or v6
plus
s wave in v1 > 35 mm

Question 25

normal ventricular conduction

Answer 25

fibres of left bundle branch begin conduction
impulse travels across interventricular septum from left to right
- small r wave v1
- small q wave v6
travels across ventricles causing depolarisation of both RV and LV
LV contributed most to complex
- deep s wave v1
- tall r wave v6

Question 26

right bundle branch block in v1

Answer 26

no change in initial impulse travel - small r wave
impulse depolarises LV by itself sing RBBB (s wave)
RV depolarises late by impulse through muscle (r’ wave)
hence rsr’ pattern - M shape
‘MaRRoW’ pattern

Question 27

left bundle branch block in v1

Answer 27

initial deflection altered since travels right to left - q wave/negative deflection
RV depolarises unopposed - may produce small r wave
travels across septum to depolarise LV - deep s wave
w pattern in v1
WiLLiaM pattern
**ST segment uninterpretable in LBBB

Question 28

st segment

Answer 28

begins at end of qrs complex
ends at beginning of t wave

Question 29

what can st segment elevation or depression indicate

Answer 29

myocardial ischaemia or infarction

Question 30

anterior st elevation

Answer 30

left anterior descending occlusion

Question 31

inferior st elevation

Answer 31

right coronary artery 80%
left circumflex 20%

Question 32

widespread ischaemia

Answer 32

probably LMS

Question 33

calculating HR - regular cardiac rhythm

Answer 33

count number of large squares between r waves
rate = 300/number

Question 34

calculating HR - irregular cardiac rhythm

Answer 34

use rhythm strip at bottom - 10 second recording
rate = number of qrs complexes x6

Question 35

bradycardia

Answer 35

any abnormality of cardiac rhythm resulting in a slow heart rate
HR < 60 bpm

Question 36

tachycardia

Answer 36

any abnormality of cardiac rhythm resulting in a fast HR
HR > 100bpm

Question 37

bradyarrhythmias

Answer 37

heart block
- first degree
- second degree
- third degree/complete HB

Question 38

1st degree av block

Answer 38

regular rhthm
pr interval > .2 seconds and is constant
causes - IHD, conduction system disease, seen in healthy children or athletes
usually doesnt require treatment

Question 39

2nd degree av block - mobitz 1/wenckebach

Answer 39

irregular rhythm
pr interval continues to lengthen until a qrs is missing (non-conducted sinus beat)
pr intervant not constant
rhythm usually benign unless associated with underlying pathology

Question 40

2nd degree av block - mobitz 2

Answer 40

irregular rhythm
qrs complex may be wide
non-conducted sinus impulses appear at irregular intervals
rhythm is somewhat dangerous as the block is lower in the conduction system
may cause syncope of may deteriorate into complete HB
appearance in setting of an acute MI identifies high risk patients
cause - IHD, fibrosis of conduction system
treatment - pacemaker

Question 41

complete heart block

Answer 41

atria and ventricles beat independent of one another - av dissociation
QRS’s and P waves each have own rhythm
may be caused by inferior MI and presence worsens the prognosis
may cause syncopal symptoms or angina, especially is ventricular rate is low
treatment - usually pacemaker +/- temporary pacing/isoprenaline

Question 42

narrow complex tachyarrhythmias

Answer 42

uncontrolled - ie fast - atrial fibrillation or flutter
atrial tachycardia
avnrt/avrt

Question 43

broad complex tachycardia

Answer 43

ventricular tachycardia
ventricular fibrillation