093014 EKG

Question 1

P wave represents

Answer 1

atrial depolarization (first right, then left, but both are combined into the P wave)

Question 2

if you prolong AP duration, what happens on the EKG?

Answer 2

prolongation of QT interval (QT interval changes can be arrhythmia-genic)

Question 3

in the heart the sequence of repolarization is opposite to that of

Answer 3

depolarization, b/c AP duration is shorter near the outer epicardium (the last cells to depolarize)

so you get a positive T wave

Question 4

precordial leads

Answer 4

in transverse plane (V1-V6)

Question 5

limb leads

Answer 5

front plane leads

Question 6

bipolar leads are leads

Answer 6

I, II, III

Question 7

aVL’s degree deflection

Answer 7

-30 degrees

Question 8

lead II’s degree deflection

Answer 8

60 deg

Question 9

if you have RBBB, what will happen on EKG?

Answer 9

prolongation of total time to depolarize the two ventricles (the left will depolarize first and then the right)

this prolongation widens out the QRS

also, get deflection of electrical activity to the right

Question 10

septal depolarization is from

Answer 10

left to right

Question 11

as lateral wall of LV is depolarized, why is depolarization directed leftward as opposed to rightward?

Answer 11

bc electrical forces of thick LV outweigh those of RV

electrical forces of thick LV-depolarization is directed leftward and posteriorly toward V6

Question 12

interpreting EKG-what to look for?

Answer 12

check voltage calibration
check heart rhythm
HR
measure intervals (PR, QRS, QT)
calculate mean QRS axis
evaluate P wave 
evaluate QRS (hypertrophy, bundle branch block, infarction)
evaluate ST/T wave

Question 13

in standard cases along vertical axis 1 mm represents?

Answer 13

0.1 mV

Question 14

time in standard horizontal axis on EKG-with recording speed of 25 mm/sec, 1mm = ?

Answer 14

0.04 seconds

Question 15

PR interval should be btwn

Answer 15

120-200 ms

Question 16

normal sinus rhythm criteria

Answer 16

every P followed by QRS
upright P in I, II, III
PR interval btwn 120 and 200 ms
HR btwn 60-100 bpm

Question 17

how to calculate HR from EKG

Answer 17

1500/ number of small boxes between two beats
or
count off 300-150-100-75-60-50

if rhythm is irregular, can count number of QRS during 6 seconds and multiply by 10

Question 18

corrected QT interval

Answer 18

measured QT/square of RR interval (seconds)

you do this because QT can vary with heart rate

other thing you can do–QT interval should normally be less of half of RR

Question 19

mean QRS axis is defined as

Answer 19

average of instantaneous lectrical ofrces generated during ventricular depolarization in the frontal plane

Question 20

normal mean QRS axis is

Answer 20

-30 to 90 deg

Question 21

how do you roughly estimate the QRS mean axis?

Answer 21

look at leads I and II- if net deflection is positive in both of these leads, the mean QRS axis is within normal range of -30 to +90 degrees.

Question 22

how to use geometric method to find mean QRS axis

Answer 22

pick any two frontal leads

draw perpendiculars from them and where they intersect is the mean axis

Question 23

how to use inspection method to find mean QRS axis

Answer 23

look for isoelectric frontal lead, then draw a perpendicular line to this lead. this perpendicular line is the mean QRS axis, but to determine which direction it’s pointing, you need to look at another lead to determine which direction

Question 24

if you have R atrial enlargement what would you see on P wave in leads II and V1?

Answer 24

in lead II-taller P wave

in lead V1-taller right atrium wave

Question 25

L ventricle hypertrophy-what would you see in lead V1?

Answer 25

deeper S wave

Question 26

L ventricle hypertrophy-what would you see in lead V6?

Answer 26

bigger QRS

Question 27

if you have L atrial enlargement what would you see on P wave in leads II and V1?

Answer 27

in lead II-a second left atrium peak

in lead V1-a deeper left atrium depression

Question 28

if you have R ventricular hypertrophy, what would you see on EKG?

Answer 28

in V1: increased R-R is greater than S

in V6: deep S

Question 29

with fascicular blocks, QRS interval is

Answer 29

reasonably normal, as opposed to bundle branch block

Question 30

with left anterior fascicle block, what is the direction of activation?

Answer 30

initial inferior followed by dominant superior direction of activation

Question 31

with left posterior fascicle block, what is direction of activation?

Answer 31

initial superior followed by dominant inferior direction of activation

Question 32

in bundle branch block, why is activation of the blocked part slow?

Answer 32

because relies on activation from cell to cell rather than rapidly conducting HIs purkinje system

Question 33

in left bundle branch block, why does the Q wave disappear in V6?

Answer 33

because you don’t have the normal left to right ventricular septum depolarization

Question 34

criteria for RBBB

Answer 34

QRS complex
RsR’ (M shaped ) QRS complex in lead I
widened or “slurred” S wave in leads I and V6

Question 35

when you have ST segment elevation, can you have reciprocal ST depression in some leads for the case of myocardial infarction?

Answer 35

yes