Approach to ECGs
- Rate
- Rhythm
- Axis
- Intervals
- P wave
- QRS complex
- ST segment / T wave
Rate
- Normal: 60-100 bpm
Rhythm
- Are P waves present?
- Is each P wave associated with each QRS, and vice versa?
Axis
- Use Leads I, II, and aVF
- Normal axis: (+) Lead I, (+) Lead II, (+) Lead aVF
Intervals (normal)
- PR: 120-200 ms (3-5 little boxes)
- QRS: 120 ms (%3C 3 little boxes)
Intervals (abnormal)
- PR interval
- Short: likely AV node origin (junctional rhythm), accessory pathways (e.g. WPW)
- Long: slow conduction through AV node (i.e. 1st degree heart block)
- QRS complex
- Wide: slow conduction - ventricular myocyte origin (myocyte to myocyte conduction is much slower than fast conducting fibres), diseased conducting fibres (bundle branch block, BBB)>)
*** P wave, etc