Editing Afterload (section)

{{Short description|Pressure in the wall of the left ventricle during ejection}}
[[File:Heart systole.svg|thumb|Ventricular systole. Red arrow is path from left ventricle to aorta. Afterload is largely dependent upon aortic pressure.]]
'''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.<ref name=":0">{{Cite book|title=Cardiovascular Physiology, 9e|author=Mohrman, David E.|date=2018|publisher=McGraw-Hill Education LLC|isbn=9781260026115|oclc=1055827575}}</ref> 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 [[Circulatory system|cardiovascular system]].<ref name=":0" /> Afterload is proportional to mean systolic blood pressure and is measured in [[millimeters of mercury]] (mm Hg).