Cleveland Clinic EKG Practice Test

Pathologic Q waves are defined as what criteria?

Q waves ≥0.04 seconds (1 small box) and ≥25% of the following R wave

Pathologic Q waves reflect a prior transmural myocardial infarction with scar tissue that no longer conducts normally. For a Q wave to be considered pathologic, it has to be both wide and deep: duration at least 0.04 seconds (the width of one small box) and depth at least one-quarter the amplitude of the following R wave. This combination distinguishes a true scar-related Q wave from normal, small Q waves seen in healthy hearts or in certain leads. The other patterns either miss one of these criteria or require an unusually large depth, so they don’t fit the standard definition.

Q waves ≥0.06 seconds and ≥50% of the next R wave

Q waves ≥0.02 seconds and ≥10% of the following R wave

Q waves ≥0.04 seconds and ≥75% of the following R wave