ECGs Flashcards
(43 cards)
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
