ECGs Flashcards
What happens to potential for the heart to contract? [1 mark]
Changes from negative to positive (relative to the inside of the cell)
What is a dipole in a heart? [1 mark]
When there’s a potential difference between one part of a myocyte and another
What is set up around a dipole in the heart? [1 mark]
An external electrical field
What happens to the potential difference in depolarisation or repolarisation? [1 mark]
No potential difference (so no electrical field)
What is a lead? [1 mark]
An electric dipole consisting of two equal and opposite charges (+q and -q)
Where does most depolarisation occur in the heart? [1 mark]
Bottom right corner
What are the three bipolar leads? [4 marks}
I, II and III (to form aVR, aVL and aVF)
Where is the V1 chest lead placed? [2 marks]]
- 4th intercostal space
- Right sternal edge
Where is the V2 chest lead placed? [2 marks]]
- 4th intercostal space
- Left sternal edge
Where is the V3 chest lead placed? [1 mark]
Equidistant to V2 and V4
Where is the V4 chest lead placed? [2 marks]]
- 5th intercostal space
- Midclavicular line
Where is the V5 chest lead placed? [2 marks]]
- Left anterior axillary line
- In horizontal line with V4
Where is the V6 chest lead placed? [2 marks]]
- Mid axillary line
- Horizontal with V4 and V5
Which leads measure the septal surface? [2 marks]
- V1
- V2
Which leads measure the anterior surface? [2 marks]
- V3
- V4
Which leads measure the lateral surface? [4 marks]
- V5
- V6
- I
- aVL (left wrist)
Which leads measure the inferior surface? [3 marks]
- II
- III
- aVF (left ankle)
What does Bachmann’s bundle do? [1 mark]
It carries impulses from the right side of the heart to the left side.
What does the left bundle of His divide into? [2 marks]
- Anterior fascicle
- Posterior fascicle
How long does the AV node delay impulses for? [1 mark]
.2 seconds
What does the P wave show? [1 mark]
Depolarisation of both atria
What is the line between the P wave and QRS complex? [1 mark]
The delay of depolarisation at the AV node.
What is the QRS complex and how long does it last for? [2 marks]
- The depolarisation and subsequent contraction of ventricles
- Lasts for 80-110ms
What is the QT interval? [2 marks]
- Ventricular depolarisation and repolarisation
- Lasts for 350-420ms
What is the ST segment? [1 mark]
Repolarisation of ventricles
What does a depressed ST segment tell us? [1 mark]
Ischaemia
What does an elevated ST segment tell us? [1 mark]
Myocardial infarction
How long does the PR interval last for? [1 mark]
~200ms
What is tachycardia? [1 mark]
Fast heartbeat
What is bradycardia? [1 mark]
Slow heartbeat
What does sinus mean? [1 mark]
It starts from the sino-atrial node
What happens to the R-R interval in sinus bradycardia? [1 mark}]
Increases
In what group is sinus arrhythmia normal? [1 mark]
Young people
What are the two types of arrhythmias? [2 marks]
- Conduction abnormalities
- Abnormal impulse initiation
What happens in sino-atrial block? [3 marks]
- No impulse from SA node
- Impulse from elsewhere
- R-R interval is irregular
What happens in atrio-ventricular block? [2 marks]
- No impulse from AV node
- No ventricular contraction
What happens in ventricular ectopics and what causes them? [2 marks]
- Extra systoles
- Caused by stimulants
What causes tachycardia? [3 marks]
- Altered automaticity
- Normal AP swings to positive again (extra depolarisations)
- Reentry of calcium
What happens in atrial fibrillation? [2 marks]
- No distinct P wave
- Abnormal R-R interval
What happens in atrial flutter? [2 marks]
- Saw tooth pattern in wave
- Because AV node keeps getting re-stimulated
Which group is most likely affected by supraventricular tachycardia? [1 mark]
Young people
What does supraventricular mean? [1 mark]
Tachycardia that originates from a location within the heart above the bundle of His.
What can cause supraventricular tachycardia? [5 marks]
- Nothing
- Exertion
- Stimulants
- Alcohol
- Beta-agonist
