ECG Quiz Topic - Pathologic Q Waves

Pathologic Q Waves

Remember that Q waves can be normal or abnormal. When abnormal, they indicate the presence of an ongoing or an old myocardial infarction. The ECG findings of a pathologic Q wave include a Q wave duration of > 40 milliseconds (one small box) or size > 25% of the QRS complex amplitude. These need to be present in at least 2 contiguous leads to be considered abnormal (lead II and III for example, not leads II and aVF). The exception is the lateral leads V6, I, and aVL where the Q wave duration only needs to be 30 milliseconds to be deemed abnormal. Remember you can localize the area of infarction with an inferior infarct showing Q waves in leads II, III, and aVF and an anterior infarction having Q waves in leads V1-V4 (causing poor R wave progression). Below are some images of examples of pathologic and normal Q waves:

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