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Q wave
The 1st negative deflection in the QRS complex.
Differential diagnosis:
1) physiologic or positional factors
a) normal variant septal Q waves
b) normal variant Q waves in V1 to V2, aVL, III & aVF
c) left pneumothorax or dextrocardia
- loss of lateral R wave progression
2) myocardial injury or infiltration
a) acute processes
- myocardial ischemia or infarction
- myocarditis
- hyperkalemia
b) chronic processes
- myocardial infarction
- idiopathic cardiomyopathy
- myocarditis
- amyloid
- tumor
- sarcoid
- scleroderma
- Chagas disease
- echinococcus cyst
3) ventricular hypertrophy or enlargement
a) left ventricular hypertrophy
- poor R wave progression
b) right ventricular hypertrophy
- poor or reversed R wave progression, especially with COPD
c) hypertrophic cardiomyopathy
- may simulate anterior, inferior, posterior or lateral myocardial infarcts
4) 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)
Related
ECG QRS complex
electrocardiogram (ECG, EKG)
Specific
septal Q wave
General
electrocardiogram feature
Figures/Diagrams
EKG: AF, PVC, anterior infarct
References
- Harrison's Principles of Internal Medicine, 13th ed.
Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 965
- Harrison's Principles of Internal Medicine, 13th ed.
Companion Handbook, Isselbacher et al (eds), McGraw-Hill
Inc. NY, 1995, pg 332