Osmosis video - Changes in pressure-volume loops

Pressure-volume loops are graphs used to study the effects of changing preload, afterload, and contractility of the heart. The pressure inside the left ventricle is plotted on the y-axis, whereas its volume is on the x-axis. A loop presents one cardiac cycle or one heartbeat comprising diastole and systole. When preload and contractility increase, it leads to an increase in the size of the pressure-volume loop. When the afterload increases, it leads to an increase in pressure and a decrease in stroke volume. This helps to keep the stroke work stable.