Auricular depolarization, ventricular diastole and
auricular systole are the events that occur in cardiac cycle
simultaneously. Cardiac cycle is the rhythmic contraction
(systole) and relaxation (diastole) of the heart chambers
that corresponds to one heartbeat. During the cardiac cycle,
blood is pumped out of the heart into the aorta and the
pulmonary artery, and blood re-enters the heart from the
vena cava and the pulmonary veins.