6. ECG Flashcards
What changes would you see on an ECG from someone with LV hypertrophy?
Taller R wave
What does the Q wave represent?
Depolarisation of the inter ventricular septum , left to right.
Why does the Q wave cause a downward deflection?
Movement obliquely away from the apex
What does the S wave represent, why does it produce a downwards deflection?
Depolarisation to the base of the ventricles, moves away from the apex.
What does the T wave represent?
Ventricular repolarisation
Why is the T wave an upwards deflection?
Repolarisation away from the apex
How many electrodes are used in a 12-lead ECG?
10 electrodes:
4 limb
6 chest
How many views does a 12 lead ECG produce?
12
What plane do the limb leads display?
Coronal plane
What are the 6 limb leads?
Unipolar: aVR, aVF, aVL
Bipolar: I, II,III
Which leads look at the inferior surface of the heart?
II, III and aVF
Which leads look at the left side of the heart?
I and aVL
Which plane do the chest leads show?
Transverse
What are the 6 chest leads?
V1-V6
Which chest leads are the septal leads?
V1 and V2
Which chest leads are the anterior leads?
V3 and V4
Which chest leads are the lateral leads?
V5 and V6
How many seconds does 1 small square on an ECG machine represent?
0.04 seconds
How many seconds does 1 large square represent?
0.2 seconds
How would you calculate the HR using an ECG if the rhythm was irregular?
Count the number of QRS complexes in 30 large squares (6 seconds) then x 10.
How would you calculate the HR using an ECG if the rhythm was regular?
300/ number of large boxes between R peaks
What is the normal length of the PR interval?
0.12-0.20 seconds (3-5 small boxes)
What is the normal length of QRS interval?
<0.12 seconds (< 3 small boxes)
What is a normal length of a QT interval?
11-12 small boxes (corrected for HR)
How would you measure the QT interval?
Start of Q-wave to end of T-wave
How would you measure PR interval?
Start of P interval to start of Q wave
How would you measure the ST segment?
End of S wave to start of T wave
What does a widened QRS suggest?
Ventricular depolarisation that are not initiated by normal conductance mechanism
What does a prolonged PR interval suggest?
Slow conduction from atria to ventricle - first degree heart block
What does a prolonged QT interval suggest?
Prolonged repolarisation of the ventricles, this can lead to arrythmias.
What colour are the limb electrodes?
Ride your green bike Right arm = red Left arm = yellow Left leg = green Right leg = black
Where should the chest leads be attached to?
V1 right 4th intercostal V2 left 4th intercostal V3 Midway between V2 and V4 V4 5th IC space in mid-clavicular line V5 5th IC space anterior axillary line V6 5th IC space mid-axillary line
