What ECG changes are most commonly observed in stable angina?

In stable angina, the most commonly observed ECG changes are ST segment depression. This is due to myocardial ischemia, where the heart muscle is not getting enough blood supply during periods of exertion or stress. The transient nature of ischemia that occurs in stable angina typically results in changes that can be seen on the ECG such as horizontal or downsloping ST segment depression. This finding indicates that there is a compromise in the myocardial oxygen supply compared to the demand, but it does not signify a full-thickness heart muscle injury, which is seen in conditions such as myocardial infarction.

ST elevation is associated with acute myocardial infarction or pericarditis and indicates more severe damage to the heart. QT prolongation is related to other cardiovascular issues and not specifically to stable angina, while ST segment normalization doesn't typically occur with stable angina as it suggests that ischemia is resolved rather than a continuous condition experienced during exertion.