What does a Q wave measuring at least one small square in width indicate?

• A. Normal heart activity
• B. Possible myocardial infarction
• C. Healthy myocardial tissue
• D. Temporary ischemia

Answer: (B)

A Q wave measuring at least one small square in width is indicative of a possible myocardial infarction, particularly a previous one. In the context of an EKG, a significant Q wave suggests that there has been damage to the heart muscle, usually due to a lack of blood supply, which leads to cell death. This is associated with the development of a myocardial infarction, where the heart tissue becomes necrotic and leaves a scar.

In normal heart activity, Q waves are typically small and may not even be measurable, indicating that they are not a sign of previous myocardial damage. Healthy myocardial tissue generally does not show significant Q waves on an EKG; any substantial Q waves point towards a past event of myocardial injury. Likewise, temporary ischemia usually manifests through changes in the ST segment or T wave rather than through the presence of abnormal Q waves, which are specifically suggestive of enduring damage to the myocardial tissue from infarction.