A client comes to the emergency department complaining of chest pain. An electrocardiogram (ECG) reveals myocardial ischemia and an anterior-wall myocardial infarction (MI). Which ECG characteristic indicates myocardial ischemia?*1 pointa. Prolonged PR intervalb. Absent Q wavec. Elevated ST segmentd. Widened QRS complex

The ECG characteristic that indicates myocardial ischemia is c. Elevated ST segment.

Here's a step-by-step explanation:

1. An ECG, or electrocardiogram, is a test that measures the electrical activity of the heartbeat.

2. Each beat of the heart is represented on the ECG as a series of waves. The "P" wave represents the electrical impulse starting in the right atrium and spreading to the left atrium, causing them to contract. The "QRS" complex represents the rapid depolarization of the right and left ventricles. They have a larger muscle mass than the atria, so the QRS complex usually has a much larger amplitude than the P wave. The "T" wave represents the ventricles returning to their resting state, or repolarizing.

3. Myocardial ischemia, a condition in which blood flow to the heart muscle is obstructed, usually by a blood clot in the coronary arteries, can cause changes in the ST segment of the ECG.

4. The ST segment is the flat section of the ECG between the end of the S wave (the second part of the QRS complex) and the beginning of the T wave. It represents the interval between ventricular depolarization and repolarization.

5. In myocardial ischemia, the ST segment is often elevated (above the baseline). This is because the lack of blood flow alters the action potential of the affected heart muscle cells, changing the way they repolarize and thus changing the appearance of the ECG.

6. Therefore, an elevated ST segment on an ECG is a characteristic sign of myocardial ischemia.