Which complex on an EKG represents a single cycle of systole?

A single cycle of systole is represented by the QT interval on an EKG. The QT interval measures the time from the beginning of ventricular depolarization, indicated by the start of the QRS complex, to the end of ventricular repolarization, marked by the end of the T wave. This interval encompasses both the electrical activation of the ventricles (systole) and their recovery (diastole).

Understanding why the QT interval represents this entire cycle is important. During the QT interval, the heart is completing the process of contraction (systole) followed by relaxation (diastole). This is a critical phase in the cardiac cycle, as it is during this time that the ventricles actively pump blood to the lungs and the rest of the body.

The other components of the EKG, such as the P wave, QRS complex, and T wave, represent different phases of the cardiac cycle. The P wave indicates atrial depolarization, while the QRS complex corresponds specifically to ventricular depolarization. The T wave represents ventricular repolarization. None of these components capture the entire cycle of systole and diastole as effectively as the QT interval does, making it the correct choice in this context.