What ECG change is typically associated with cardiac ischemia?

T-wave inversion is typically associated with cardiac ischemia due to its role in reflecting changes in the repolarization process of the heart's ventricular myocardium. During ischemia, the affected myocardial cells experience a disturbance in their electrical activity. This disturbance can lead to alterations in the T-wave appearance on an ECG. Specifically, T-wave inversion indicates that the repolarization of the ventricle is taking place in a manner that is atypical, often resulting from underlying ischemic conditions.

T-wave inversion can be seen during both acute and chronic ischemic events and serves as a significant marker for the presence of myocardial ischemia. It suggests that there may be an insufficient blood supply to the heart muscle, affecting its electrical activity.

The other changes to the ECG mentioned, such as significant Q waves and ST-segment elevation, while also related to ischemia, tend to indicate more severe or more advanced events such as myocardial infarction, rather than murkier states of ischemia that would present primarily with T-wave inversions. U-waves are generally not associated with ischemia and may indicate other conditions, such as electrolyte imbalances.