In right bundle-branch block, ST-segment depression in the anterior precordial leads is not useful for diagnosing what condition?

In the context of right bundle-branch block, the presence of ST-segment depression in the anterior precordial leads primarily indicates altered ventricular repolarization patterns rather than directly signifying the presence of ischemia. While ST-segment depression is often associated with ischemic conditions, in the case of right bundle-branch block, this pattern can occur without any underlying ischemic process occurring, making it a non-specific finding.

The physiological changes that occur with right bundle-branch block can mask or mimic ischemic changes. Therefore, relying on ST-segment depression in this specific scenario would not reliably contribute to a diagnosis of ischemia since it could arise from other conduction abnormalities or repolarization effects. This distinguishes it from the other conditions listed which can be assessed more accurately in the presence of right bundle-branch block.