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. Technically, a Q wave indicates that the net direction of early ventricular depolarization (QRS) electrical forces projects toward the negative pole of the lead axis in question. Although prominent Q waves are a characteristic finding in myocardial infarction, 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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- Mirvis, DM, Goldberger, AL. Electrocardiography. In: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 11th ed, Zipes DP, Libby P, Bonow RO, et al (Eds), W.B. Saunders Company, Philadelphia 2017.
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- Pirwitz MJ, Lange RA, Landau C, et al. Utility of the 12-lead electrocardiogram in identifying underlying coronary artery disease in patients with depressed left ventricular systolic function. Am J Cardiol 1996; 77:1289.
- 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