Patient Care Technician (PCT) AAH Practice Exam

The ST segment on an electrocardiogram indicates what event in the heart cycle?

1. The time during which ventricles are relaxing

2. The time during which atria are contracting

3. The time during which ventricles are contracting and emptying

4. The time between heartbeats

The correct answer is: The time during which ventricles are contracting and emptying

The ST segment on an electrocardiogram represents the brief period during which the ventricles are contracting and emptying. This segment follows the QRS complex, which depicts the depolarization of the ventricles, leading to their contraction. During the ST segment, the ventricles continue to contract and pump blood out of the heart, while the heart muscle cells are in a state of depolarization, preparing for the next phase of the cardiac cycle. This period is essential for evaluating the heart's functionality, especially in diagnosing conditions like ischemia or infarction, where changes in the ST segment can indicate underlying heart problems. Understanding the significance of the ST segment is vital for patient care technicians, as it provides crucial information regarding a patient’s cardiac health. The other components of the heart cycle do not correspond to the ST segment: the time during which the ventricles are relaxing occurs during the T wave, the time during which atria are contracting is indicated by the P wave, and the time between heartbeats is referred to as the cardiac cycle or interval, none of which align with the definition of the ST segment.