What indicates a pathological Q wave on an EKG?

A pathological Q wave on an EKG is characterized by its significant amplitude relative to the preceding R wave. The correct choice highlights that a Q wave is considered pathological when it is greater than 1/3 the amplitude of the R wave. This threshold is important because it signifies that there has been notable myocardial damage or necrosis, typically associated with a previous myocardial infarction.

In a healthy heart, Q waves are generally small and transient. However, when significant damage occurs, as noted in conditions like acute coronary syndrome, the heart tissue becomes electrically altered, leading to deeper and wider Q waves. Therefore, the greater amplitude in relation to the R wave serves as a critical diagnostic indicator of underlying heart pathologies, including past myocardial infarctions.

The other options do not meet the criteria set for pathological Q waves. For instance, Q waves that are less than 1/4 the amplitude of the R wave or even exactly 1/2 the amplitude do not indicate significant myocardial damage. Furthermore, a Q wave simply being present in lead V1 does not provide sufficient diagnostic information without considering its amplitude and the context of the overall EKG.