Pathogenesis and diagnosis of Q waves on the electrocardiogram
- Ary L Goldberger, MD
Ary L Goldberger, MD
- Section Editor — Electrocardiography
- Professor of Medicine
- Harvard Medical School
By definition, a Q wave on the electrocardiogram (ECG) is an initially negative deflection of the QRS complex. Thus, a Q wave indicates that the net direction of early ventricular depolarization forces is oriented away from (by more than 90º) the positive axis of the lead in question. Although prominent Q waves are a characteristic finding in myocardial infarction (MI), they can also be seen in a number of noninfarct settings. Failure to appreciate the other causes of Q waves can lead to important diagnostic errors. (See "Basic principles of electrocardiographic interpretation".)
●Physiologic and positional effects
●Myocardial injury or replacement
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- PHYSIOLOGIC AND POSITIONAL EFFECTS
- MYOCARDIAL DAMAGE AND REPLACEMENT
- ALTERED CONDUCTION
- Left bundle branch block
- Wolff-Parkinson-White syndrome
- Left anterior fascicular (hemi-) block
- VENTRICULAR ENLARGEMENT
- Chronic obstructive pulmonary disease
- Acute pulmonary embolism
- Hypertrophic cardiomyopathy
- Depressed left ventricular function
- AIDS TO DIFFERENTIAL DIAGNOSIS