Contraction (systole) begins after an approximately 50 ms delay and results in closure of the mitral valve. The left ventricle contracts isovolumetrically until the ventricular pressure exceeds the systemic pressure, which opens the aortic valve and results in ventricular ejection.

When does the period of ejection begin?

Ejection begins when the intraventricular pressures exceed the pressures within the aorta and pulmonary artery, which causes the aortic and pulmonic valves to open. Blood is ejected because the total energy of the blood within the ventricle exceeds the total energy of blood within the aorta.

What happens ejection phase?

As pressure in the ventricles rises above two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase. Following ventricular repolarization, the ventricles begin to relax (ventricular diastole), and pressure within the ventricles drops.