The pressure required to establish this volume is the preload. The ventricle must develop sufficient pressure to exceed that in the aorta before ventricular volume can decrease during the cardiac cycle. Aortic pressure during ejection is the afterload . D. Left ventricular function throughout the cardiac cycle can be visualized as a pressure volume loop, which combines the two pressure volume relationships. Shortly after ventricular contraction begins, the mitral valve closes and the ventricle contracts isovolumetrically until intraventricular pressure exceeds aortic pressure.
Ejection begins as pressure in the ventricle exceeds that of the aorta and the aortic valve opens.
Pressure continues to rise during ejection until the ejection curve intersects the active tension curve. Further ejection and relaxation cause ventricular pressure to fall. When ventricular pressure falls below aortic pressure, the aortic valve closes and isovolumetric relaxation ensues. When ventricular pressure falls below atrial pressure the mitral valve opens and the filling phase begins. Tension increases at constant radius causing increased pressure.