Afterload 598676 212657236 2008-05-15T18:26:55Z 198.54.202.102 Heart expels blood against diastolic blood pressure [[Image:Heart systole.png|thumb|Ventricular systole. (Red arrow is path from left ventricle to aorta. Afterload is largely dependent upon aortic pressure.]] In [[cardiology|cardiac]] [[physiology]], '''afterload''' is used to mean the tension produced by a chamber of the [[heart]] in order to [[contraction|contract]]. If the chamber is not mentioned, it is usually assumed to be the [[left ventricle]]. However, the strict definition of the term relates to the properties of a single cardiac myocyte. It is therefore only of direct relevance in the laboratory; in the clinic, the term '''end-systolic pressure''' is usually more appropriate, although not equivalent. Afterload can also be described as the pressure that the chamber of the heart has to generate in order to eject blood out of the chamber, and thus is a consequence of the [[arterial pressure]], since the pressure in the ventricle must be greater than the systemic pressure in order to open the [[aortic valve]]. Everything else held equal, as afterload increases, [[cardiac output]] decreases. ==Pathology== Disease processes that increase the [[left ventricle|left ventricular]] afterload include increased [[blood pressure]] and [[aortic valve]] disease. [[Hypertension]] (Increased [[blood pressure]]) increases the [[left ventricle|left ventricular]] afterload because the left ventricle has to work harder to eject blood into the aorta. This is because the aortic valve won't open until the pressure generated in the left ventricle is higher than the elevated blood pressure. [[Aortic stenosis]] increases the afterload because the left ventricle has to overcome the pressure gradient caused by the stenotic aortic valve in addition to the blood pressure in order to eject blood into the [[aorta]]. For instance, if the blood pressure is 120/80, and the aortic valve stenosis creates a trans-valvular gradient of 30 [[mmHg]], the left ventricle has to generate a pressure of 110 mmHg in order to open the aortic valve and eject blood into the aorta. [[Aortic insufficiency]] increases afterload because a percentage of the blood that is ejected forward regurgitates back through the diseased aortic valve. This leads to elevated [[systole|systolic]] blood pressure. The diastolic blood pressure would fall, due to regurgitation. This would result in an increase pulse pressure. [[Mitral regurgitation]] ''decreases'' the afterload. During ventricular systole, the blood can regurgitate through the diseased [[mitral valve]] as well as be ejected through the aortic valve. This means that the left ventricle has to work less to eject blood, causing a decreased afterload. Afterload is largely dependent upon aortic pressure. == See also == * [[Preload (cardiology)|Preload]] * [[Cardiac output]] ==External links== * {{eMedicineDictionary|afterload}} * [http://www.cvphysiology.com/Cardiac%20Function/CF008.htm Overview at cvphysiology.com] {{Cardiovascular physiology}} [[Category:Cardiology]] [[de:Nachlast]] [[pl:Obciążenie następcze]]