amount of blood ejected by the ventricle with each beat
Ejection fraction In a healthy 70-kilogram (150 lb) man, the stroke volume is approximately 70 mL and the left ventricular end-diastolic volume (EDV) is 120 mL, giving an ejection fraction of  70⁄120, or 0.58 (58%).
Systole When the smaller, upper atria chambers contract in late diastole, they send blood down to the larger, lower ventricle chambers. When the lower chambers are filled and the valves to the atria are closed, the ventricles undergo isovolumetric contraction (contraction of the ventricles while all valves are closed), marking the first stage of systole. The second phase of systole sends blood from the left ventricle to the aorta and body extremities, and from the right ventricle to the lungs. Thus, the atria and ventricles contract in alternating sequence. The left and right atria feed blood, at the same time, into the ventricles. Then, the left and right ventricles contract simultaneously as well.