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AfterloadIn cardiacphysiology, afterload is the tension produced by a chamber of the heartin order to contract. If the chamber is not mentioned, it is usually assumed to be the left ventricle. 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. In the case of the left ventricle, the afterload is a consequence of the blood pressure, since the pressure in the ventricle must be greater than the blood pressure in order to open the aortic valve. Disease processes that increase the left ventricularafterload include increased blood pressureand aortic valvedisease. Hypertension(Increased blood pressure) increases the left ventricularafterload 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 stenosisincreases 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 150 mmHg in order to open the aortic valve and eject blood into the aorta. Aortic insufficiencyincreases afterload because a percentage of the blood that is ejected forward regurgitates back through the diseased aortic valve. This leads to elevated systolicblood pressure. Mitral regurgitationdecreases the afterload. During ventricular systole, the blood can regurgitate through the diseased mitral valveas 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.de:Nachlast Categories: Cardiology
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