Figure 1.

Left ventricular pressure-volume diagram. Pressure-volume loops obtained during an end-expiratory pause. At the lower-left corner (red circle), the mitral valve opens, and the ventricle starts rapidly to fill up during diastole. This stage concludes with the atrial contraction at the end-diastolic pressure (P_ed) and volume (EDV) (lower-right corner, blue circle). Then, the mitral valve closes, and the isovolumetric contraction phase starts. When the intraventricular pressure exceeds the aortic pressure, the aortic valve opens (upper-right corner, red circle), and the ventricle ejects decreasing intraventricular volume until end-systolic volume (ESV) and end-systolic pressure (P_es) (upper-left corner, blue circle). When the aortic valve closes, there is an intraventricular pressure decrease without any change in volume (the isovolumetric relaxation phase). When the intraventricular pressure drops below the atrial pressure, the mitral valve opens, and the cardiac cycle starts again.