ECG - Normal ECG Flashcards
What does the P-wave correspond to?
Atrial depolarisation

What does the QRS complex correspond to?
Ventricular depolarisation

What does the T-wave correspond to?
Ventricular repolarisation

What does positive deflection indicate on an ECG wave?
Depolarisation moving towards the positive electrode causes a positive, or upwards, deflection on the ECG.

What does a negative deflection on an ECG wave indicate in terms of direction of electrical flow?
- Depolarisation moving away from the positive electrode
- Repolarisation towards a positive electrode
Draw the vectors of leads I, II and III, aVR, aVF and aVL
I = L Arm to R Arm
II = R Arm to L leg
III = L Arm to L Leg
What are the positions of V1 to V6 chest leads?
- V1 - 4th intercostal space, right parasternal edge
- V2 - 4th intercostal space, left parasternal edge
- V3 - between V2 and V4
- V4 - 5th intercostal space, midclavicular line
- V5 - 5th intercostal space, anterior axillary line
- V6 - 5th intercostal space, midaxillary line

Which leads look at the left lateral surface?
I and aVL, V5 and V6

Which leads look at the inferior surface?
II, III and aVF

Which leads look at the right atrium?
aVR

Which leads look at the IV septum?
V1 + V2

Which leads look at the anterior walls of the left ventricle?
V3 and V4

What should the ECG running speed be set to?
25 mm/s
How many seconds are in a large square?
0.2 seconds
How many seconds are in a small square?
0.04 seconds
How long should the PR interval be?
0.12 - 0.2 s (3-5 small squares)
How long should a QRS complex be?
<0.12 s (<3 small boxes)
How long should the QT interval last in men at 60 BPM?
< 0.45 s
What determines the magnitude of deflection (either up or down) on an ECG recording?
The magnitude of the deflection is determined by how parallel the electrical force is to the axis of the lead being examined. The more parallel, the greater the magnitude of deflection

If the electrical force was directed perpendicular to an ECG lead, what would be recorded?
The lead would not register any activity

What is the sequence of normal cardiac activation?
https://www.youtube.com/watch?v=zBj6btjdYHU
- Atrial depolarisation (right and left)
- Delay at AV node
- Impulse travels to bundle of His
- Impulse moves into the right and left bundle branches
- Impulse carried along purkinje fibres

What does the R wave of the QRS complex represent?
https://www.youtube.com/watch?v=zBj6btjdYHU
Depolarisation of the bulk of the ventricle from the endocardial to the epicardial surface

What are the criteria for normal sinus rhythm?
- HR - 60–100 BPM
- Regular Rhythm
- “P” wave present - ratio of 1:1, represents SA node is pacing
- Normal PR interval - between 0.12 and 0.20 second.
- Normal QRS complex - <0.12 second.
How can you calculate HR from an ECG?
Rhythm strip at the bottom
Method 1
- Count the number of R-waves in 30 large squares (6 seconds)
- Multiply by 10 to get number of beats over 60 seconds
Method 2
- Rate = 300 / number of large squares in between each consecutive R wave.
Method 3
- Rate = 1500/number of small squares between R waves


