What does the Q-T portion of an EKG represent?

The Q-T interval on an electrocardiogram (EKG or ECG) represents the time it takes for the heart to depolarize and then repolarize the ventricles, which corresponds to the electrical activity involved in the ventricular contraction phase. This interval begins at the onset of the Q wave and ends at the end of the T wave.

During the Q-T interval, the ventricles are actively contracting (systole) and then transitioning back to a relaxed state as they prepare for the next heartbeat. This period encapsulates both the time the ventricles are contracting (systole) and the time they are in the process of relaxing (diastole), but importantly, the most significant part is the contraction characterized by the rise and fall of electrical activity during a heartbeat.

Understanding this interval is crucial, as abnormalities in the Q-T interval can lead to serious cardiac arrhythmias. Thus, recognizing that the Q-T interval is primarily associated with systolic activity gives an important insight into the dynamics of the cardiac cycle.