Session 7 Lecture Notes - ECG abnormalities Flashcards
What are supraventricular rhythms and give some examples?
They are rhythms that have been generated anywhere up to and including the AV node Examples: SA node (normal) Atrium AV node
In a supraventricular rhythm what width would the QRS complex be?
3 small squares (0.12 seconds)
The QRS would therefore be normal (narrow)
What would the QRS complex look like in ventricular rhythm and why?
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
What lead does the rhythm strip of the ECG show?
Limb Lead II
What HR is sinus bradycardia?
Less than 60 BPM
What HR is sinus tachycardia?
Over 100 BPM
What are the key ECG features of AF?
- No P wave (quiver on baseline as the atrial depolarisation is chaotic)
- 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)
What would you see on an ECG in first degree heart block?
What is the treatment?
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
Where does heart block usually occur?
At the AV node
What is mobitz type 1 secondary heart block also known as?
The wenkebach phenomenon
What would you see on an ECG of a person with mobitz type 1 secondary heart block?
PROGRESSIVELY longer PR intervals until 1 P wave is not conducted (No QRS complex follows it)
PR interval resets and the cycle repeats
What would you see on an ECG of a person with mobitz type 2 secondary heart block?
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
Which heart block is more dangerous - mobitz type 1 or 2 secondary heart block?
Type 2 = it can progress to type 3 (complete) heart block
What would you see on an ECG of a person with third degree heart block?
The P waves and QRS complex are unrelated (no relationship)
The atria and ventricles are conducting independently from one another
In ventricular ectopic beats what would the QRS complex look like on the ECG and why?
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
How many ventricular ectopic beats need to appear in a row before it is defined as ventricular tachycardia?
More than 3 ventricular ectopic beats in a row
What can ventricular ectopic beats lead to?
Ventricular fibrillation
In ventricular fibrillation will you get a normal QRS complex?
Does this differ to atrial fibrillation?
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
Which 4 leads have a lateral view of the heart?
- I
- Chest lead V5
- Chest lead V6
- Limb lead aVL (left wrist)
What 2 leads have a septal view of the heart?
- Chest lead V1
2. Chest leads V2
What 3 leads have an inferior view of the heart?
- II
- III
- Limb lead aVF (right foot)
Which 2 leads have an anterior view of the heart?
- Chest lead V3
2. Chest lead V4
Which area of the heart is most vulnerable to ischaemic damage and why?
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
What size does a Q wave need to be to be considered pathological?
Over 1 square wide
Over 2 squares deep
What is a STEMI and what will it show on ECG?
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
What are the values for hypo and hyperkalaemia?
Hyperkalaemia = high levels of serum potassium (over 5mmol) Hypokalaemia = low levels of serum potassium (below 3.5mmol)
In hyperkalaemia what will you see on the ECG?
What is this similar to and why?
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
What will be the difference in T wave size in hypokalaemia and hyperkalaemia?
Hyperkalaemia = tall T waves Hypokalaemia = small T waves
