What does the T wave indicate?

The T wave on an electrocardiogram (ECG) represents the relaxation or repolarization of the ventricles. After the ventricles contract during the QRS complex, they need to return to their resting state. This process is visually represented by the T wave. During this time, the ventricles undergo a recovery phase that prepares them for the next cycle of contraction. The T wave is essential for understanding the heart's electrical activity, as it signifies the time when the ventricles are refilling with blood and getting ready for the next heartbeat. This phase is critical for maintaining proper heart rhythm and function.

The other options refer to different aspects of the cardiac cycle or the electrical activity of the heart. For instance, the contraction of the ventricles occurs during the QRS complex, not the T wave. The electrical activity of the atria is indicated by the P wave. Blood flow through the heart valves is not directly represented on an ECG; rather, it is a physiological process that occurs as a result of the electrical impulses that the ECG records. Understanding the role of the T wave provides insight into the cyclical nature of cardiac depolarization and repolarization, which is vital for effective heart function.