Final answer:
The QT interval on an ECG is the measure of time from the onset of the QRS complex, representing ventricular depolarization, to the end of the T wave, which indicates ventricular repolarization.
Step-by-step explanation:
The QT interval on an electrocardiogram (ECG) represents the period starting from the onset of the QRS complex to the end of the T wave. It is a measure of the time taken for both ventricular depolarization and repolarization, which essentially represents the total time taken by the ventricles to undergo a single cycle of depolarization and repolarization.The QRS complex is a crucial part of the ECG and represents the depolarization of the ventricles, the main pumping chambers of the heart. The T wave follows the QRS complex and signifies the repolarization of the ventricles, essentially when the ventricles are preparing for the next heartbeat. Both are key elements in understanding the cardiac cycle, which is the period of time between the onset of atrial contraction (atrial systole) and ventricular relaxation (ventricular diastole).