w6 electrocardiogram theory

Question 1

what is a lead axis

Answer 1

the that current between two electrodes flows from negative to positive

Question 2

what are the direction of the waves on ecg related to (general answer)

Answer 2

the direction of the current created by leads of ecg

• direction of current flow in cardiac muscle.
• waves on ecg are either up or down this is because there is a directional relationship between the lead axis and cardiac vector.

Question 3

what is cardiac vector

Answer 3

the direction of electrical current produced by the patients heart, it is also known as vector.

Question 4

what is a bipolar lead

Answer 4

two sensors attached to two electrodes, one is positive and one is negative.

Question 5

baseline or isoelectric

Answer 5

thesis when the ecg is turned on but not detecting electrical current, it is a straight line
-occur between waves. waves are then formed when chambers contract

Question 6

what are the waves on ecg

Answer 6

the waves produced are a comparison between the line of electricity set up between sensors on the body and the general direction of the electrical current of patients heart

Question 7

what happens to wave when vector in same direction of lead axis

Answer 7

large positive, upward deflection

Question 8

cardiac vector flow opposite direction of lead axis

Answer 8

large negative or below baseline deflection

Question 9

cardiac current or vector at angle but in same direction of lead axis

Answer 9

small upward or positive deflection

Question 10

cardiac current or vector at an angle to but in the opposite general direction of lead axis

Answer 10

small downward or negative deflection

Question 11

cardiac current or vector parallel to lead axis

Answer 11

isoelectric line or biphasic/equiphasic deflection (equal positive and negative waves)

Question 12

lead 1

Answer 12

electrode on right arm is negative and left arm is positive

-this deflection would be small positive deflection because it is in the same direction but it is not parallel

Question 13

lead 2

Answer 13

electrode on right arm is negative and electrode on left leg is positive (goes across body from right to left)
-this deflection would be large and a positive deflection because it is the same direction as the vector.

Question 14

lead 3

Answer 14

left arm is now negative and electrode on left leg is positive (runs from left shoulder to left leg)
-this deflection would be small and positive because it is in the same direction of vector but not parallel

Question 15

electrical current direction of heart

Answer 15

downward ad to the left and it is the same direction as lead 2 axis

Question 16

rhythm strip

Answer 16

lead 2 is the rhythm strip because it is in the same direction of the heart and it can detect irregularities in the cardiac rhythm it provides the most classical PQRST wave

Question 17

Einthoven’s Triangle

Answer 17

-It is the triangle created by the leads and it related to Einthoven’s law which is the voltage in lead 2 is equal to the sum of the voltages in lead 1 and 3 – you measure the HEIGHT OF THE R WAVES

Question 18

zero point

Answer 18

when lines are draw through midpoint of each lead perpendicular to axis the three lines intersect at the centre of the heart and this is the zero point

Question 19

how are unipolar leads created?/what are they?

Answer 19

two sensors are joined together with the intersection point being zero point at centre of heart. the heart is made the negative terminal and only the exploring positive electrode is used – simplified–the heart is the negative terminal and the sensors on the right arm left leg and left arm are used as single positive terminals

Question 20

A V R L F

Answer 20

a-signals augmented deflections are small without amplification
v-voltage
r-positive electrode on right arm 
l-postive electrode on left arm
f-postive electrode on leg or foot

Question 21

aVR

Answer 21

lead axis connecting the centre of the heart to the positive electrode on the right arm

Question 22

aVL

Answer 22

lead axis connection the centre of the heart to positive electrode at left arm

Question 23

aVF

Answer 23

views heart from axis connection the centre of the heart to the positive electrode at the left leg

Question 24

what is a precordial lead? and what do they view

Answer 24

the v1-v6 leads used on chest- view horizontal plane and record forces moving anteriorly and posteriorly which means front to back and left to right. **horizontal plane

• the precordial leads are unipolar -exploring electrode positive.
• lead axis is from centre of heart to positive exploring electrode

Question 25

what do 6 limb leads view

Answer 25

electrical forces in the frontal plane: up and down left and right

Question 26

where are precordial leads v1 to v6 placed?

Answer 26

v1-4th intercostal space on right side of sternum
v2-4th intercostal rib on left side of sternum
v3- 5th rib
v4-5th intercostal space mid-clavicular
v5- 5th intercostal space shoulder
v6-5th intercostal space mid-axilla(armpit)

Question 27

R wave progression

Answer 27

QRS complex seen as ventricular depolarization occurs. the complex changes from negative in v1 to positive in v6- R wave will get bigger. this is because the leads run in the same direction and parallel to the vector

Question 28

where will tallest r wave be seen

Answer 28

when lead is running parallel and in the same direction to vector, this occurs in lead v5– the change is r wave progression

Question 29

R wave in v1 and v2

Answer 29

start out small

Question 30

r wave in v3

Answer 30

equiphasic which means v3 is perpendicular to the heart

Question 31

r wave in v4

Answer 31

similar to v5

Question 32

r wave in v6

Answer 32

generally smaller in v6

Question 33

why will QRS complex vary in precordial leads?

Answer 33

because each person may have different positioning of their heart in the chest cavity