Isovolumetric Relaxation:
The Beginning of Diastole

• Ventricular diastole begins with the ventricles continuing to relax and intraventricular pressure falling to a point where the total energy of the blood within the ventricles is less than the energy of blood in the outflow tracts
• This pressure reversal causes the aortic and pulmonic valves to abruptly close
• Ventricular pressures decrease despite the fact that volumes remain constant because all the valves are closed