ECG reading Flashcards
A small square on an ECG graph represents how many seconds?
40ms (0.04 seconds)
One large square on an ECG graph represents how many seconds?
200ms (0.2 seconds)
What does the ‘P’ wave represent?
Atrial contraction
What does the ‘QRS’ complex represent?
Ventricular contraction
What does the ‘T’ wave represent?
Ventricular relaxation
What does a broad QRS complex indicate?
Left and right ventricles aren’t contracting at the same time
Which ECG leads are measuring the inferior region of the heart? (3)
Leads II, III and AVF
Which ECG leads are measuring the anterior region of the heart? (4)
Leads V1, V2, V3 and V4
On an ECG, 5 large squares represent how much time?
1 second
Heart rate can be measured by the number of large squares between R - R intervals. What does 1 large square equate to in terms of heart rate?
300bpm
If there are 3 squares in the R - R interval, what is the heart rate?
100bpm
What is the normal time of the PR interval?
120-200ms (3-5 small squares)
Where should the chest leads V1 and V2 attach on the body?
VI on the (patients) right hand side, 4th intercostal space sternal edge
V2 on the (patients) left hand side, 4th intercostal space sternal edge
Where should chest leads V3 and V4 attach on the body?
V4 should attach on the patients left hand side, 5th intercostal space in the midclavicular line
V3 should attach in between V2 and V4 (on the 4th rib)
Where should chest leads V5 and V6 be placed on the body?
V6 should be in the mid axillary line along from V4
V5 should be in between V4 and V6.
To work out if the cardiac axis is in the normal direction, which leads parts of the ECG should be used?
I, II and III.
Which part on the ECG recording will indicate the cardiac axis?
QRS complex
In an ECG reading with a normal cardiac axis, which QRS complex should be most positive?
II
In a right axis deviation, which QRS complex is most positive?
III (this is the right inferior-lateral region of the heart, which makes sense for right axis deviation as it is generally caused by right ventricular hypertrophy).
How does left axis deviation occur on an ECG reading in leads II and III?
Both have negative QRS complexes.
What would first degree heart block look like on an ECG reading?
- P-R interval prolonged = 360ms
- One P wave per QRS complex
(essentially just prolonged P - R interval)
What pathologies can first degree heart block signify?
- Coronary artery disease
- Acute rheumatic carditis
- Digoxin toxicity
- Electrolyte disturbances
What are the two types of second degree heart block?
Type 1 Mobitz - AKA Wenckebachs
Type 2 Mobitz
What will the ECG reading look like in Wenckebachs second degree heart block?
There is a progressive lengthening of the P-R interval, for example it could go; 260ms, 280ms, 320ms. A QRS complex will then be dropped, and another P wave will come along, and the progressive lengthening recommences.
What happens in type 2 Mobitz second degree heart block?
The ‘P-R’ interval of the conducted beats is constant, but there is a dropped QRS complex, often in a pattern of for example 2:1 or 3:1. Meaning after 3 normal cycles, a QRS complex is dropped. There is sometimes no pattern though.
There is another type of second degree heart block, called 2:1, what does this refer to?
There are two P waves for every QRS complex. The anomaly/initial P wave may be disguised in the T wave or S wave.
What is third degree heart block?
Atrial contraction is normal, but no beats are conduced to the ventricles. The ventricles natural pacemaker which is a lot slower, than takes over. The ECG reading will show regular P waves, but they have no relation to the random QRS complexes.
Why might third degree heart block have occurred?
In patients with an MI or it may be a chronic state due to fibrosis of the bundle of His.
If the P wave is tall on an ECG, what can this indicate?
P pulmonale - right atrial hypertrophy (most commonly due to tricuspid stenosis)
If the P wave is broad on an ECG, what can this indicate?
P mitrale - left atrial hypertrophy (most commonly due to mitral stenosis)
