Like all things in Medicine, it is crucial to be systematic when approaching the ECG. This gives a breakdown of the important parts of the ECG trace to be aware of and questions to ask yourself when interpreting a recording. Read ‘the ECG made easy’ to learn more!
1. Check Patient name, details, date and time of ECG and the indication
Knowing the indication will help you to focus in on the problem. However, it is also important to look at the whole ECG.
2. Rate
A tachycardia is a rate more than 100 bpm, bradycardia is a rate of less than 60 bpm.
3. Rhythm
Is the rhythm irregular or regular? (regularly irregular or irregularly irregular?)
Is it sinus rhythm? (i.e. are there P waves a regular distance before each QRS complex, and is each P wave followed by a QRS complex?)
4. Axis
This essentially represents the direction in which the heart depolarises. It should be between -30° and +90°. A full explanation of this is complex and best left to other sources e.g. the ‘ECG made easy’.
5. P waves
Are there P waves present? Are there P waves present before every QRS complex?
Is every P wave followed by a QRS complex?
6. PR interval
Is the distance between the start of the P wave and the start of the QRS complex less than 0.2 seconds (less than 5 of the small squares)? Is this distance always the same?
7. QRS complex
Is this narrow (less than 3 small squares, normal) or broad (more than 3 small squares)
8. ST segment
Is the ST segment raised or lowered relative to the PR interval? What leads are these changes seen in?
These are the typical patterns of myocardial infarction and ischaemia respectively
9. T waves
Are there any T waves inverted? This is seen in myocardial infarction.
Are there tented T waves? This is seen in hyperkalaemia
10. Summary of findings and differential diagnosis
This will get better with practice!