Electrocardiogram

Question 1

ECG

Answer 1

Body surface recording of a change in electrical potential which is a projection of the net potential changes occurring in hearth

Question 2

Horizontal axis ECG

Answer 2

1 mm section, One square equals 0.04 sec

Question 3

Vertical axis ECG

Answer 3

A 10 mm deflection equals 1 mV

at rest placed as vert midpoint

Question 4

Isoelectric line

Answer 4

Vert midpoint of paper 0 mv
Upward deflection is +
Downward deflection is -

Question 5

P-wave

Answer 5

represents atrial depolarization

sum of all phase 0’s in atrial tissue

Question 6

P-R interval

Answer 6

Amount of time from beginning of P wave to beginning of QRS complex. ). 0.12 to 0.20 sec.
(less embryo kent bundle)

Question 7

First degree block

Answer 7

PR excessively long
Conduction through AV node is reduced.
All P wave still have a QRS

Question 8

Second degree block

Answer 8

Not all P waves have a QRS .

Some do not pass through AV node. 1:1

Question 9

Third degree block

Answer 9

No P waves conduct through AV node complete block

Question 10

QRS complex

Answer 10

sequential depolarization of the ventricular cells.

Duration 80ms over 120 ms conduction defect R & L block

Question 11

S-T segment

Answer 11

Long period through phase 2. Non polar plateau

Question 12

Acute injury and S-T

Answer 12

Phase 2 would be something other than 0
Lack of current flow
OLD INFARCTS don’t show ST shift

Question 13

T wave

Answer 13

Ventricular depolarization Summation of phase 3’s

Question 14

U wave

Answer 14

May represent repolarization of the papillary muscles or purkinje conduction system

Question 15

ECG Phase 0 atrial

Answer 15

P wave

Question 16

ECG Phase 0 ventricular

Answer 16

QRS complex

Question 17

ECG Phase 3 ventricular

Answer 17

T wave

Question 18

Normal duration of PR and QRS

Answer 18

PR 140 ms

QRS 80-120 ms

Question 19

ECG Unipolar limb leads

Answer 19

AVR, AVL & AVF.

Compare voltage diff btw 1 point and ground

Question 20

ECG AVR ex

Answer 20

+ lead on R arm, - lead on L arm & L leg.

R lead bisects the angle created by intersection of Leads I and II perpendicular to lead III

Question 21

ECG bipolar limb leads

Answer 21

Measures diff btw two points on the body.
Equilateral ( Einthoven’s) triangle formed.
Analyzes ECG in frontal plane
Ex RA, LA & LL

Question 22

Describe the unipolar chest leads

Answer 22

i. V1 – 4th intercostal space, rt sternal border
ii. V2 – 4th intercostal space, lt sternal border
iii. V3 – midway between V2 and V4 on line joining two points
iv. V4 – 5th intercostal space, midclavicular line (left side)
v. V5 – Anterior axillary line same level as V4
vi. V6 – Mid axillary line same level as V4 and V5
b. Analyze ECG in horizontal plane

Question 23

Formula

Answer 23

HR = 1/n x chart speed
Select 2 points
Count number of large boxes (n)

Question 24

Counting method

Answer 24

Memory 6 300,150,75, 60 & 50

Question 25

Division by 300

Answer 25

number of boxes

ex: 300/4 = 75

Question 26

Marked paper

Answer 26

hospital use paper with intervals in seconds

ex: 3 sec measure six and multiply by 10

Question 27

Describe the hexaxial reference system in the frontal plane

Answer 27

Utilizes equilateral triangle leads I, II, III & unipolar chest lead
Center point id AV
Axis leads move to intersect AV at midpoint
Augemented voltage lead superimposed to get degree

Question 28

Normal axis

Answer 28

0 to 90 degree

Question 29

Right axis deviation

Answer 29

90 to 180 degree
End of deep inspiration
Moving to standing position
Tall stature
Hypertrophy (pulmonary valve stenosis, pulmonary hypertension, congenital malformations)
Right bundle branch block (signal travels faster in normal LV)
Wide QRS

Question 30

Left axis deviation

Answer 30

0 to - 90 degree
End of deep expiration
Supine posture
Obesity
Hypertrophy (systemic hypertension, valvular disease, congenital)
Left bundle branch block (signal travels faster in normal RV)
Also shows wide QRS

Question 31

Approximation of mean degree

Answer 31

a. Select any two leads 90 degrees apart from each other (lead I and AVF are convenient because they are horizontal and vertical respectively)
b. Evaluate the QRS in lead I (if deflected in positive direction, vector point to left (positive pole))
c. Evaluate QRS in AVF (if deflection is positive, arrow points down (towards positive pole))
d. Use vector addition to determine the resultant mean axis