Which of the following is a component of the cardiac cycle depicted on an ECG?

The U wave is a recognized component of the cardiac cycle as depicted on an ECG. It typically follows the T wave and can represent the repolarization of the Purkinje fibers or the ventricular myocardium. While it is not always present in every ECG tracing and tends to be small and not always clinically significant, its presence can give insight into the heart's electrical activity, particularly in conditions such as hypokalemia or other electrolyte imbalances.

The other options, such as V wave, X wave, and Y wave, do not have established roles or representations within the standard cardiac cycle as analyzed through an ECG. Therefore, while the U wave is an integral part of the ECG, the other waves listed do not contribute to the common interpretations of the cardiac cycle and are not recognized components within standard ECG analysis.