Lecture 05/06: Basic Concepts of ECG: Lead System, Measurement, Normal Rhythms (Sosa, Estrada)

Question 1

Magnitude of potential is dependent on 3 things:

Answer 1

1) strength of the source
2) distance from the electrodes to the dipole
3) angle of line from the electrode to the midpoint of the dipole

Question 2

standard lead system

Answer 2

bipolar lead system. Lead II most often read

Question 3

Lead I lead placement in bipolar lead system

Answer 3

RA -

LA +

Question 4

Lead II lead placement in bipolar lead system

Answer 4

RA-

LL+

Question 5

Lead III lead placement in bipolar lead system

Answer 5

LA-

LL+

Question 6

Augmented Unipolar limb leads

Answer 6

avR (RA+), avL (LA+), avF (LF+)

Question 7

ECG is good for detecting ______ but not as good at detecting _____

Answer 7

rhythm abnormalities; chamber enlargement

Question 8

Positioning animal for ECG

Answer 8

RLAT recumbency with limbs perpendicular to body preferably on mat

Question 9

faster paper speed is good to use when HR is

Answer 9

fast

Question 10

slow paper speed is good for:

Answer 10

rhythm analysis

Question 11

ECG artifact

Answer 11

ECG abnormality not due to cardiac disorder (i.e. electrical interference, purring, trembling). Do NOT change the HR

Question 12

Four basic determinations of ECG

Answer 12

1) heart rate
2) rhythm analysis
3) measurements for analysis of cardiac size
4) MEA

Question 13

coupling interval

Answer 13

interval between normal sinus beat and ensuing premature beat

Question 14

ectopic beat

Answer 14

disturbance of cardiac rhythm, usually because rhythm is being generated from somewhere other than SA node

Question 15

sinus rhythm

Answer 15

normal rhythm with P for every QRS

Question 16

nonconductive P wave

Answer 16

P wave not followed by QRS

Question 17

Supraventricular rhythm

Answer 17

“above the ventricle.” narrow, upright in lead II. Uses rapid conduction system. +/- P wave

Question 18

ventricular rhythm

Answer 18

cannot use the rapid conduction system; wide/bizarre rhythm with no related P wave. less than 90% like normal

Question 19

ventricular premature complex

Answer 19

negative premature complex, wide, bizarre, less than 90% like normal

Question 20

supraventricular premature complex

Answer 20

narrow, upright, more than 90% like normal, but premature beat

Question 21

width of P wave relates to:

Answer 21

duration

Question 22

height of P wave relates to:

Answer 22

voltage

Question 23

PR interval

Answer 23

start of P to start of QRS complex

Question 24

QRS width

Answer 24

beginning of Q to baseline after S

Question 25

R wave height

Answer 25

baseline to R peak

Question 26

ST segment (height)

Answer 26

depression or elevation relative to baseline

Question 27

QT interval

Answer 27

from beginning of QRS to end of T

Question 28

ST segment (width)

Answer 28

from end of QRS to beginning of T

Question 29

Can there be ST without S wave?

Answer 29

Yes

Question 30

QT interval varies inversely with:

Answer 30

HR

Question 31

Mean Electrical Axis

Answer 31

average direction that a wavefront of dipoles is moving in the heart. Applied to QRS complex

Question 32

2 methods for determining MEA:

Answer 32

1) Isoelectric lead method (look at lead that is perpendicular to isoelectric lead)
2) Major Deflection Method (look at lead with major deflection. all 6 leads required for this method)

Question 33

Normal MEA range

Answer 33

+30 to +120 degrees

Question 34

Left axis shift range

Answer 34

-90 to +30 degrees

Question 35

Right axis shift range

Answer 35

-90 to +120 degrees

Question 36

Axis shift indicates:

Answer 36

mean depolarization wave had to take a different path to get to lead. (i.e. more mass –> more shift)