Q wave
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Introduction
The 1st negative deflection in the QRS complex.
Differential diagnosis
- physiologic or positional factors
- normal variant septal Q waves
- normal variant Q waves in V1 to V2, aVL, III & aVF
- left pneumothorax or dextrocardia
- loss of lateral R wave progression
- myocardial injury or infiltration
- acute processes
- myocardial ischemia or infarction
- myocarditis
- hyperkalemia
- chronic processes
- acute processes
- ventricular hypertrophy or enlargement
- left ventricular hypertrophy
- poor R wave progression
- right ventricular hypertrophy
- poor or reversed R wave progression, especially with COPD
- hypertrophic cardiomyopathy
- may simulate anterior, inferior, posterior or lateral myocardial infarcts
- left ventricular hypertrophy
- conduction abnormalities
- left bundle branch block (poor R wave progression)
- Wolf-Parkinson-White syndrome
Abnormal QRS deflection associated with myocardial infarction, should be at least 30 ms in duration, > 1/4 the size of the R-wave & present in 2/3 inferior leads.
| Q wave | infarction | |
|---|---|---|
| V1, V2 | anteroseptal | |
| V1, V2 | (if tall R) | posterior |
| V3, V4 | apical | |
| I, aVL, V5, V6 | anterolateral | |
| II, III, aVF | inferior | |
| V1, V2, V3 | Wolf-Parkinson-White (WPW) |