ECG

Question 1

What is an ECG?

Answer 1

ECG is a recording of the electrical activity of the heart from the skin

Question 2

What does the P wave represent?

Answer 2

Atrial depolarisation

Question 3

What does the QRS complex represent?

Answer 3

Ventricular depolarisation

Question 4

What does the PQ interval represent?

Answer 4

Delay through the AV node

Question 5

What does the St segment show?

Answer 5

Plateau phase of repolarisation

Question 6

What does the T wave show?

Answer 6

Repolarisation of ventricle

Question 7

What are the 2 types of lead-in ECG and what is the difference between the two?

Answer 7

Unipolar: measures the potential variation at a single point (single electrode)

Bipolar: measures the potential difference between two points

Question 8

How many leads does a typical ECG have?

Answer 8

12

Question 9

What is the name of the wiring you attach the actual skin?

Answer 9

Electrode

Question 10

What are the unipolar leads?

Answer 10

Augmented Limb leads:
aVR (right shoulder), aVL (left shoulder), aVF (left Leg)
Chest leads: V1-V6

Question 11

what are the bipolar leads?

Answer 11

Limb leads: I, II, III
I = Right Arm to Left Arm
II = Right Arm to Left Leg
III = Left Arm to Left Leg

all should make a triangle

Question 12

What is a lead?

Answer 12

Lead = electrical vector: angle and direction of an electrical impulse

Question 13

What planes do each of the leads work in:

Answer 13

Coronal plane: Limb leads

Transverse plane: Chest leads

Question 14

Whats the rule for placing electrodes?

Answer 14

Either put them all on proximally or all on distally

e.g. either wrist and ankles or shoulder and thighs

Question 15

What is the anterior heart surface assessed by?

Answer 15

V1-V4 e.g. damage to Anterior Left Descending Artery

Question 16

What is the inferior heart surface assessed by?

Answer 16

Limb leads: II, III and aVF (foot lead)

Question 17

What is the lateral heart surface assessed by?

Answer 17

V5, 6, Lead I, aVL

Question 18

What gives a positive deflection on the ECG?

Answer 18

DEPOLARISATION OF THE HEART towards the positive electrode

Question 19

What gives a negative deflection on the ECG?

Answer 19

Depolarisation of the heart away from the positive electrode

Question 20

what effect does depolarisation of the heart parallel to the positive electrode have?

Answer 20

Positive deflection as it approaches and negative deflection as it moves away

Question 21

outline a systemic approach to the interpretation of ECG

Answer 21

Get clinical context of patient 
Check patient details match (date, time)
Assess technical quality 
if many artefacts then redo
check paper speed
Gain

Go to the rhythm strip (continuous across page)
identify P/QRS/T
measure heart rate 
check ECG intervals 
determine QRS axis 

Looking at 12 leads:
Look at PQRST morphology

Question 22

How do you calculate the HR from ECG?

Answer 22

count the number of squares between each QRS interval and then do 300 divided by the number

Question 23

What is the normal QRS interval speed

Answer 23

120 ms

Question 24

what is a normal QRS axis?

Answer 24

between +90 to - 30 degrees

Question 25

What is bundle branch block and what effect will it have on QRS complex?

Answer 25

When one of the limbs of the conducting system is not working. QRS Complex is longer than 120 ms.

Question 26

what effect does acute coronary occlusion have on ECG?

Answer 26

Elevated ST segment