Which of the following can indicate myocardial ischemia on an ECG?

Myocardial ischemia refers to a condition where there is insufficient blood flow to the heart muscle, often due to blockages in the coronary arteries. One of the main ways to detect myocardial ischemia is through changes observed on an electrocardiogram (ECG). The elevation or depression of the ST segment is particularly significant in this regard.

When myocardial ischemia occurs, the heart muscle may not receive enough oxygen and nutrients, affecting its electrical activity. This can lead to characteristic changes in the ST segment on an ECG. Specifically, ST segment elevation can indicate myocardial infarction (a more severe form of ischemia), while ST segment depression may suggest angina or less severe ischemic conditions. These changes arise due to altered repolarization of the cardiac muscle and can be crucial for diagnosis and determining the urgency of treatment.

The other options may provide useful information about the heart's electrical activity, but they do not specifically indicate myocardial ischemia. For instance, the QRS complex duration can reflect the conduction velocity through the ventricles but does not directly signal ischemia. The RR interval, which measures the time between heartbeats, is useful for assessing heart rate but is not indicative of ischemic events. Changes in the P wave could suggest abnormalities in