ECGs

Question 1

ECG lead I measures conduction in what aspect of the heart?

Answer 1

Left lateral

Question 2

ECG lead II measures conduction in what aspect of the heart?

Answer 2

Left lateral

Question 3

ECG lead III measures conduction in what aspect of the heart?

Answer 3

Inferior

Question 4

aVR lead measures conduction in what aspect of the heart?

Answer 4

Right atrium

Question 5

aVL lead measures conduction in what aspect of the heart?

Answer 5

Left lateral

Question 6

aVF lead measures conduction in what aspect of the heart?

Answer 6

Inferior

Question 7

V1 lead measures conduction in what aspect of the heart?

Answer 7

Right ventricle

Question 8

V2 lead measures conduction in what aspect of the heart?

Answer 8

Right ventricle

Question 9

V3 lead measures conduction in what aspect of the heart?

Answer 9

Interventricular septum

Question 10

V4 lead measures conduction in what aspect of the heart?

Answer 10

Interventricular septum

Question 11

V5 lead measures conduction in what aspect of the heart?

Answer 11

Left ventricle

Question 12

V6 lead measures conduction in what aspect of the heart?

Answer 12

Left ventricle

Question 13

Which leads are said to be bipolar?

Answer 13

Red, yellow and green limb leads

Question 14

What is first degree heart block (also called AV block)?

Answer 14

Slowing of conduction through the AV node meaning ventricles take longer to depolarise

Question 15

How is first degree/AV block recognised on an ECG?

Answer 15

Prelonged P-R interval of more than 0.2 seconds

Question 16

What is third degree heart block?

Answer 16

Complete blockage of conduction anywhere downstream of the AV node

Question 17

How is third degree/complete heart block recognised on an ECG?

Answer 17

P wave : QRS complex appear completely unrelated with distorted firing ratio (eg. 8 p waves for each QRS complex)

Bradycardia

Question 18

Third degree heart block is complete blockage of conduction anywhere downstream of the AV node. Based on this, why is there still ventricular firing seen on an ECG trace?

Answer 18

Ventricles form a ventricular subsidiary pacemaker. This is able to initiate a separate heart beat at around 40bpm

Question 19

What is atrial fibrillation?

Answer 19

Rapid and irregular beating of the atria initiated by electrical activity independent of the SA node

Question 20

What are the consequences of prelonged and sustained courses of AF?

Answer 20

Irreversible electrical remodelling

Question 21

AF is initiated by rapid electrical activity independent of the SA node. From where does this independent activity of AF often come from?

Answer 21

Arrythmogenic foci located in muscular sleeves of pulmonary veins

Question 22

How is AF recognised on an ECG?

Answer 22

Irregularly irregular pulse
Absence of a clear P wave
PR interval immeasurable

Question 23

How is ST elevation recognised on an ECG?

Answer 23

ST segment elevated greater than 1mm in 2 or more limb leads OR 2mm or more in 2 or more chest leads

Question 24

What limb lead measures conduction in the horizontal axis?

Answer 24

Lead I

Question 25

What limb lead measures conduction in the vertical axis?

Answer 25

aVF

Question 26

What are the precordial ECG leads? What do they measure?

Answer 26

V1 to 6 Electrical activity on a transverse plane

Question 27

What are the augmented leads?

Answer 27

aVR aVL aVF

Question 28

What are the bipolar limb leads?

Answer 28

Lead I Lead II Lead III

Question 29

What are the two factors that determine ECG deflection?

Answer 29

``` Flow direction (towards/away from the electrode) Depolarisation/repolarisation ```

Question 30

Depolarisation travelling towards an electrode would produce a ......... deflection?

Answer 30

Positive

Question 31

Repolarisation travelling towards an electrode would produce a ......... deflection?

Answer 31

Negative

Question 32

Depolarisation travelling away from an electrode would produce a ......... deflection?

Answer 32

Positive

Question 33

Repolarisation travelling away from an electrode would produce a ......... deflection?

Answer 33

Negative

Question 34

A current travelling neither towards nor away from an electrode would produce a ........ deflection?

Answer 34

No deflection