At the start of ventricular systole the AV valves close and the ventricular pressure increases. Left and right ventricular pressure rises to a maximum of about 120 mm Hg and 25 mm Hg, respectively. The AV valves are pulled down into the ventricle by the contraction of the ventricular muscle. About 70-90 ml of blood is ejected with each stroke, but about 50 ml remains in each ventricle. Cardiac output, an important index of cardiac function, is the product of stroke volume and heart rate.
Ventricular diastole begins with as the pressure drops and the aortic and pulmonary valves close.
When the ventricular pressure falls below the atrial pressure the AV valves open and blood begins to quickly fill the ventricles.