A first look at the ECG

Question 1

In which direction is an electrical signal travelling if the ECG blip is positive going?

Answer 1

The signal is travelling towards the electrode

Question 2

In which direction is an electrical signal travelling if the ECG blip is negative going?

Answer 2

The signal is travelling away from the electrode

Question 3

Which leads are the standard limb leads?

Answer 3

I, II & III

Question 4

Which leads are the augmented limb leads?

Answer 4

aVR, aVL & aVF

Question 5

Which leads are the chest leads?

Answer 5

V1-V6

Question 6

Which plane do the standard limb leads (I-III) look at the heart in?

Answer 6

The frontal plane

Question 7

Which limbs are connected by standard limb lead I?

Answer 7

Left and right arm

Question 8

Which limbs are connected by standard limb lead II?

Answer 8

Left and right arm

Question 9

Which limbs are connected by standard limb lead III?

Answer 9

Left leg and right arm

Question 10

What does each aspect of the QRS represent?

Answer 10

Q= The small negative going blip at the start of the QRS is the inter ventricular septum depolarising from left to right

R= depolarisation of the ventricle towards the electrode (positive going blip)

S= The upper part of the interventricular septum depolarises in a cranial direction (away from the the electrode)

Question 11

In which direction does the heart repolarise?

Answer 11

From the top towards the apex (same direction as depolarisation)

Question 12

What causes a change in the size of the QRS complex on the ECG tracing?

Answer 12

Hyper or hypotrophy will cause the anatomy of the heart, and therefore the orientation of electrical signals, to shift slightly

As the position of the interventricular septum shifts, the direction that the electrical signal travels changes slightly and it may be detected more or less on certain leads.

Question 13

What is a normal PR interval?

Answer 13

0.12-0.2s

Question 14

What is happening in the heart during the PR interval?

Answer 14

The electrical signal is bing transmitted through the AV node

Question 15

What is the usual time associated with the QRS complex??

Answer 15

0.8s

Question 16

What is a normal QT interval at a resting heart rate of around 60?

Answer 16

0.42 seconds

Question 17

Why is it not possible to see atrial repolarisation on an ECG?

Answer 17

Atrial repolarisation is lost within the QRS complex because there are far more ventricular cells than atrial cells so the electric signal is much stronger coming from the ventricles

Question 18

In which augmented limb lead is depolarisation picked up best?

Answer 18

aVF

Question 19

Why is the ECG trace inverted in aVR?

Answer 19

Because the depolarisation is moving away from this lead

Question 20

Why is the trace very small in aVL?

Answer 20

because this lead is the furthest from the direction of depolarisation

Question 21

In which plane do the chest leads look at the heart?

Answer 21

Horizontal

Question 22

Describe what is meant by “progression” in the chest leads

Answer 22

Progression is when the ECG trace flips from a negative-going blip to a positive-going blip between the chest leads (Progression usually occurs somewhere between leads V2/V3/V4)

Question 23

Whic chest leads should always show;
A) A negative-going blip
B) A positive-going blip

Answer 23

A) V1

B) V6

Question 24

At what speed should ECG paper run at?

Answer 24

25mm/s

Question 25

How can you tell if the ECG paper is running at the correct speed

Answer 25

If the paper is running at the correct speed, the calibrating pulse should take up one large box

Question 26

How can you work out heart rate from a rhythm strip?

Answer 26

Count how many QRD complexes there are in 30 large boxes then multiply it by 10

Question 27

What is classed as tachycardia?

Answer 27

A heart rate >100BPM

Question 28

What is classed as bradycardia?

Answer 28

A heart rate <60BPM

Question 29

What is a normal heart rate?

Answer 29

60-100BPM

Question 30

What is the acronym used to read an ECG.

Answer 30

ARIBAR

A= any electrical activity?
R= Rate 
I= Irregular or regular rhythm
B= Broad QRS complexes 
A=Any P-waves?
R= Relationship between the P-wave and the QRS complex?