Afterload

Afterload is the pressure that the heart must work against to eject blood during systole (ventricular contraction). Afterload is proportional to the average arterial pressure.^[1] As aortic and pulmonary pressures increase, the afterload increases on the left and right ventricles respectively. Afterload changes to adapt to the continually changing demands on an animal's cardiovascular system.^[1] Afterload is proportional to mean systolic blood pressure and is measured in millimeters of mercury (mm Hg).