Introduction/Objectives: In the cardiac cycle, should a coupling phase be considered between systole and diastole where cardiac suction occurs? Shouldn't the left ventricular ejection fraction be considered a poor reliability index? According to these considerations, would it not be more logical to speak of cardiac energy of suction and ejection as parameters that summarize the cardiac potential and to which variables that are not independent would concur. Materials and Methods: The concept of energy is incorporated by means of a detailed evaluation of the cardiac ability developed by both ventricles as a counterpart of ejection fraction values to assess ventricular function. The heart in its pump function, presents a dynamic effect that is greater than the volume it ejects. Data involving patients will have informed consent. Results: Understanding the active mechanism of the suction phase as a link between systole and diastole opens a wide scenario on surgical techniques and medical treatments for many cardiac diseases that are still the focus of attention. Conclusion: The important incorporation of other disciplines such as physics and hydraulics has allowed the evaluation of cardiac mechanics from pre-existing laws that denote and justify what the heart really represents: a mechanical suction pump. The understanding of cardiac functions is achieved from the cardiac structure-function and from a physico/hydraulic point of view.