EKG- Class 1

Question 1

phases of cardiac pacemaker cell

Answer 1

phase 4: Na influx If channels
phase 0: Ca influx
phase 3: K efflux

Question 2

difference between cardiac muscle and pacemaker cell AP voltages:

Answer 2

muscle cell: -90 to +10

pacemaker cell: -60 to +10

Question 3

Q wave

Answer 3

first negative deflection

Question 4

R wave

Answer 4

first positive defection

Question 5

S wave

Answer 5

second negative deflection

Question 6

PR interval

Answer 6

beginning of P to beginning of QRS

120-200msec (3-5boxes)

Question 7

QTc is corrected with ___ and ___ dependent

Answer 7

HR; sex

Question 8

causes of prolonged QTc:

Answer 8

drugs, genetics, metabolic disturbances (dangerous!)

Question 9

which is longer, segment or interval?

Answer 9

interval is always longer

Question 10

U wave

Answer 10

uncommon; after T wave; indicates purkinje fibers

Question 11

intrinsic pacemaker rhythms:

Answer 11

SA node: 60-100
AV node: 45-50
His: 40-45
Ventr cells/purkinje: 20-40

Question 12

which His bundle has ant/post divisions?

Answer 12

left

Question 13

which type of heart block is considered an escape rhythm?

Answer 13

third degree (bc rhythm not driven by SA node)

Question 14

limb leads:

Answer 14

I, II, III, aVR, aVL, aVF

Question 15

limb lead for forces going to the upper right

heart

Answer 15

aVR

Question 16

limb lead for forces moving to left lateral heart

Answer 16

aVL

Question 17

limb lead for forces moving to inferior heart

Answer 17

aVF

Question 18

electrical trend of precordial leads:

Answer 18

V1/2: negative, V3/4: isoelectric, V5/6: positive

Question 19

Degrees of Limb Leads I-III (when calculating axis)

Answer 19

I: 0
II: +60
III: + 120

Question 20

Degrees of Augmented Limb leads

Answer 20

aVL: -30
aVF: +90
aVR: -150

Question 21

Heart Rate Box intervals:

Answer 21

300/150/100, 75/60/50, 43/37

Question 22

leads used in rule of thumbs

Answer 22

I and aVF (both should be positive)

Question 23

If lead I is + and aVF is negative, which lead should be used to check if true left axis deviation?

Answer 23

lead II (if negative, true LAD)

Question 24

LAD axis:

Answer 24

-30 to -90

Question 25

RAD axis:

Answer 25

+90 to +180

Question 26

no mans land axis:

Answer 26

-90 to +180

Question 27

what does an equiphasic lead mean?

Answer 27

depolarization occurs perpendicular to the lead

Question 28

Causes of Right axis deviation:

Answer 28

lateral MI
COPD
pumonary embolus
Right ventricular hypertrophy
nl in kids/tall thin adults (athletes)
dextrocardia

Question 29

Causes of Left axis deviation:

Answer 29

LBBB
inferior MI
artificial pacing
left ventricular hypertrophy