Normal Q waves are narrow (average 0.02 seconds and less than 0.03 seconds), are usually less than 5mm deep in left precordial leads and aVF but may be as deep as 8mm in lead 3 in children younger than 3 years.
Q waves are abnormal if they:
- Appear in the right precordial leads i.e. V1 (e.g. severe RVH)
- Are absent in the left precordial leads (LBBB)
- Are abnormally deep (ventricular hypertrophy of the volume overload type)
- Are abnormally deep and wide (myocardial infarction or fibrosis)