Abstract The cardiac cycle is a series of physiological events in which blood moves through the chambers of the heart in alternating phases of systole and diastole. Movement of blood throughout the cardiac chambers is dependent on pressure changes and gradients, generated by alternating contraction and relaxation of myocardium. The cardiac cycle is generally described as having four phases: filling phase, isovolumetric contraction, ejection phase, and isovolumetric relaxation. Each of these phases is regulated by the cardiac conduction system, a complex network of specialized myocytes that ensures synchronized contraction and relaxation of myocardium.