Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Pathogenesis and diagnosis of Q waves on the electrocardiogram

Ary L Goldberger, MD
Section Editor
David M Mirvis, MD
Deputy Editor
Gordon M Saperia, MD, FACC


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".)

The presence of a Q wave does not indicate any specific electrophysiological mechanism. To the contrary, Q waves can be related to one or more of the following four factors (table 1) [1,2]:

Physiologic and positional effects

Myocardial injury or replacement

Ventricular enlargement

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Apr 03, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Goldberger, AL, Goldberger, ZD, Shvilkin AS. Goldberger’s Clinical Electrocardiography: A Simplified Approach, 9th edition, Elsevier, Philadelphia, 2017.
  2. 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.
  3. Delewi R, Ijff G, van de Hoef TP, et al. Pathological Q waves in myocardial infarction in patients treated by primary PCI. JACC Cardiovasc Imaging 2013; 6:324.
  4. 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.