OSCE interpretation Flashcards
What is the normal calibration of an ECG
25 mm/s and 10 mm/1mV
Normal adult’s heart rates?
Normal: 60-100 bpm
Tachycardia: > 100 bpm
Bradycardia: < 60 bpm
2 methods to calculate HR on ECG
Why might you choose one over the other?
- 300 / number of large squares
- 6 x number of QRS in 10 seconds
Only the second option works for irregularly irregular rhythms
Normal cardiac axis?
In healthy individuals, you would expect the axis to lie between -30° and +90º
Normally, if the electrical activity is towards a lead then this lead positive. The closer to it, the more positive the lead is.
Describe right axis deviation
- Depolarisation is distorted to the right
- Between 90 and 180
- Moves toward leads III, away from lead II and massively away from lead I
- See increased positivity in III, slightly less positivity in II and almost negativity in lead I
Describe left axis deviation
- Depolarisation is distorted to the left
- Between - 30 and - 90
- Moves towards aVL, far away from III, and away from II to the other side of I
- Lead III is hugely negative
- Lead II is negative
- Lead I is positive
What to look for with P waves
- Are they present?
- Is so, are they each followed by a QRS?
- Do the P waves look normal? Duration, direction, shape
- If P waves are absent, is there any atrial activity?
o Sawtooth baseline –> flutter waves
o Choatic baseline –> fibrillation waves
o Flat line –> no atrial activity at all
Normal PR interval
120 - 200 ms (1.2 - 2 s)
3-5 small squares
Shortened PR interval causes?
- P wave is originating from somewhere closer to AV node so conduction takes less time - some people have smaller atria, or SA node is not in fixed place
- Atrial impulse is getting to the ventricle via a faster shortcut, e.g. accessory pathway, Wolf-Parkinson White syndrome
- Would see delta waves in WPW syndrome
Three things to look at with QRS
- Width
- Height
- Morphology
Width of QRS
- Narrow (< 0.12 seconds)
- Broad (> 0.12 seconds)
Causes of broad QRS
- Bundle branch block
- Ventricular ectopics
- Ventricular arrhythmias
Causes of narrow QRS
- Atrial ectopics
Height of QRS
- Small (< 5 mm in limb leads or < 10 mm in chest leads)
- Tall - imply ventricular hypertrophy
Morphology problems of QRS
- Delta waves (WPW if with tachyarrhythmias)
- Q waves
What are pathological Q waves
> 25% the size of the R wave that follows it
OR
2mm in height and > 40ms in width
R and S waves
- In lead V1 the S wave is larger than the R wave
- The transition to R being the larger wave should occur in lead V3 or V4
- If it occurs into V5 or V6 this is poor R wave progression
- Can be a sign of previous MI or in very large people due to poor lead position
ST elevation in mm/squares
- > 1 mm (1 small square) in 2 or more contiguous limb leads
OR - > 2 mm in 2 or more chest leads
ST depression in mm/squares
- > 0.5 mm in > 2 contiguous leads
T waves
Tall
> 5 mm in limb leads
AND
10 mm in chest leads
T waves
Tall
Height
> 5 mm in limb leads
AND
10 mm in chest leads
T waves
Tall
Causes
- Hyperkalaemia
- Hyperacute STEMI
T waves
Inversion
Causes
- Ischaemia
- Bundle branch block
- PE
- LVH
- HOCM
- General illness
Biphasic T waves
Causes
- Ischaemia
- Hypokalaemia
Flattened T waves
Causes
- Ischaemia
- Electrolyte imbalances
U waves
What are they?
- > 0.5 mm deflection after the T wave
- Best seen in V2 or V3
U waves
Causes
- Electrolyte imbalances
- Hypothermia
- Secondary to antiarrhythmic therapy (digoxin, amiodarone)
What does a small square on an ecg represent
0.04 seconds
What does a large square on an ecg represent
0.2 seconds
ECG: How many large squares in 1 second
5
ECG: How many large squares in 1 minute
300
Spirometry
Reference ranges
FEV1: >80% predicted
FVC: >80% predicted
FEV1/FVC ratio: >0.7
Spirometry
Details that need to be checked
Name Age Gender Height Ethnicity
