Session 7 Lecture Notes - ECG abnormalities

Question 1

What are supraventricular rhythms and give some examples?

Answer 1

They are rhythms that have been generated anywhere up to and including the AV node
Examples:
SA node (normal)
Atrium 
AV node

Question 2

In a supraventricular rhythm what width would the QRS complex be?

Answer 2

3 small squares (0.12 seconds)

The QRS would therefore be normal (narrow)

Question 3

What would the QRS complex look like in ventricular rhythm and why?

Answer 3

It would be wider (over 3 small squares)
This is because in ventricular rhythm the conduction has not spread through the AV node and down the His-Purkinje conduction system
The ventricular myocytes have to spread conduction from cell to cell which takes longer

Question 4

What lead does the rhythm strip of the ECG show?

Answer 4

Limb Lead II

Question 5

What HR is sinus bradycardia?

Answer 5

Less than 60 BPM

Question 6

What HR is sinus tachycardia?

Answer 6

Over 100 BPM

Question 7

What are the key ECG features of AF?

Answer 7

1. No P wave (quiver on baseline as the atrial depolarisation is chaotic)
2. QRS complex = irregularly irregular
   It depends on when the impulse arrives and this is not in a regular fashion
   The QRS complex itself will look normal (depolarisation of ventricle is still taking place)

Question 8

What would you see on an ECG in first degree heart block?

What is the treatment?

Answer 8

You would see a longer PR interval (more than 5 small squares)
The P wave and QRS complex itself would appear normal
You do not need to give treatment

Question 9

Where does heart block usually occur?

Answer 9

At the AV node

Question 10

What is mobitz type 1 secondary heart block also known as?

Answer 10

The wenkebach phenomenon

Question 11

What would you see on an ECG of a person with mobitz type 1 secondary heart block?

Answer 11

PROGRESSIVELY longer PR intervals until 1 P wave is not conducted (No QRS complex follows it)
PR interval resets and the cycle repeats

Question 12

What would you see on an ECG of a person with mobitz type 2 secondary heart block?

Answer 12

Normal PR intervals
Normal P wave and QRS complex
Occasionally a P wave will not be followed by a QRS complex
It is more dangerous than Mobitz type 1 because it can progress to complete heart block

Question 13

Which heart block is more dangerous - mobitz type 1 or 2 secondary heart block?

Answer 13

Type 2 = it can progress to type 3 (complete) heart block

Question 14

What would you see on an ECG of a person with third degree heart block?

Answer 14

The P waves and QRS complex are unrelated (no relationship)

The atria and ventricles are conducting independently from one another

Question 15

In ventricular ectopic beats what would the QRS complex look like on the ECG and why?

Answer 15

It would be wide and an unusual shape because conduction hasn’t gone through the His-Purkinje system so it is much slower to conduct
QRS complexes may appear earlier than expected as they conduct before signal is sent from SA node

Question 16

How many ventricular ectopic beats need to appear in a row before it is defined as ventricular tachycardia?

Answer 16

More than 3 ventricular ectopic beats in a row

Question 17

What can ventricular ectopic beats lead to?

Answer 17

Ventricular fibrillation

Question 18

In ventricular fibrillation will you get a normal QRS complex?
Does this differ to atrial fibrillation?

Answer 18

No there is chaotic, fast and abnormal ventricular depolarisation so no co-ordination contraction = ventricles quiver rather than contract
This differs to AF in which the QRS complex is normal

Question 19

Which 4 leads have a lateral view of the heart?

Answer 19

1. I
2. Chest lead V5
3. Chest lead V6
4. Limb lead aVL (left wrist)

Question 20

What 2 leads have a septal view of the heart?

Answer 20

1. Chest lead V1

2. Chest leads V2

Question 21

What 3 leads have an inferior view of the heart?

Answer 21

1. II
2. III
3. Limb lead aVF (right foot)

Question 22

Which 2 leads have an anterior view of the heart?

Answer 22

1. Chest lead V3

2. Chest lead V4

Question 23

Which area of the heart is most vulnerable to ischaemic damage and why?

Answer 23

The subendocardial region
It is furthest away from epicardium where coronary arteries lie
If these are damaged this is the last place (furthest away) to be perfused

Question 24

What size does a Q wave need to be to be considered pathological?

Answer 24

Over 1 square wide

Over 2 squares deep

Question 25

What is a STEMI and what will it show on ECG?

Answer 25

STEMI = myocardial infarction from complete blockage of coronary artery
You will see raised ST segment
These will merge will tall T waves
You will eventually see Q waves developing = muscle necrosis

Question 26

What are the values for hypo and hyperkalaemia?

Answer 26

Hyperkalaemia = high levels of serum potassium (over 5mmol)
Hypokalaemia = low levels of serum potassium (below 3.5mmol)

Question 27

In hyperkalaemia what will you see on the ECG?

What is this similar to and why?

Answer 27

You will see tall T waves
The ST segment may becomes encorporated into the T wave upstroke
This is similar to acute myocardial infarction
This could be because in M.I you get damaged myocytes (release of larger amount of potassium) which could lead to localised hyperkalaemia

Question 28

What will be the difference in T wave size in hypokalaemia and hyperkalaemia?

Answer 28

Hyperkalaemia = tall T waves
Hypokalaemia = small T waves