What condition may lead to "ST segment depression"?

ST segment depression on an electrocardiogram can indicate underlying cardiac issues, most notably associated with myocardial ischemia. Myocardial ischemia refers to a reduced blood flow to the heart muscle, often due to coronary artery disease. It is characterized by an imbalance between oxygen supply and demand. When the heart muscle is not receiving enough oxygen, it can lead to changes in the ST segment of the ECG, manifesting as depression. Additionally, digoxin toxicity can also produce similar ST segment changes due to its effects on cardiac contractility and electrical conduction.

The other options describe conditions that are either unrelated to the specific changes seen in the ST segment or present different clinical implications. Bradycardia represents a slow heart rate but does not typically produce ST segment changes; chronic hypertension may affect overall heart function over time but is not specifically associated with ST segment depression. Normal physiological responses, such as exercise or increased heart rate, generally lead to ST segment elevation rather than depression, while heart valve disorders primarily influence the structure and function of the heart but do not typically cause ST segment changes directly.