What does the T-wave denote in an ECG?

The T-wave in an electrocardiogram (ECG) represents ventricular repolarization, making it a crucial component in understanding cardiac function. During the cardiac cycle, the heart undergoes electrical changes that lead to muscle contraction and relaxation.

After the muscle cells of the ventricles have contracted to pump blood out of the heart, they must reset their electrical state to prepare for the next heartbeat. This resetting process is known as repolarization, which is indicated by the T-wave. It follows the QRS complex, which represents ventricular depolarization—when the ventricles contract. The T-wave shows that the ventricular muscle fibers are returning to their resting state, allowing the heart to fill with blood again before the next contraction.

In summary, the T-wave is essential because it reflects the recovery phase of the ventricles and signals that they are ready for the next cycle of contraction, making it a critical marker in assessing the heart's health and rhythm.