In aortic stenosis, you get a decrease in stroke volume and cardiac output, thus you eject less blood and thus have a larger end systolic volume [increased residual volume]. But WHY does end diastolic volume and pressure increase? According to texts, the NORMAL venous return adds to the increased residual volume thus increasing preload or end diastolic volume and pressure. But why is this? If you eject less then shouldn't that smaller stroke volume return to the heart thus maintaining end diastolic volume? Since the circulatory system is a closed system, then cardiac output has to equal venous return. Thus, if you have a decreased cardiac output, which you do with aortic stenoisis, then you should have a reduce venous return, thus maintaining your end diastlic volume and pressure [preload].
So, when texts say that the normal venous return adds to the increased residual volume causing an increase in end diastolic pressure and volume [preload] isn't that wrong? Shouldn't the end diastolic pressure and volume [preload] stay the same since the previous stroke volume was less?
Following is the link which shows the PV-loop for aortic senosis for your reference:
http://www.oucom.ohiou.edu/cvphysiology/HD009.htm
So, when texts say that the normal venous return adds to the increased residual volume causing an increase in end diastolic pressure and volume [preload] isn't that wrong? Shouldn't the end diastolic pressure and volume [preload] stay the same since the previous stroke volume was less?
Following is the link which shows the PV-loop for aortic senosis for your reference:
http://www.oucom.ohiou.edu/cvphysiology/HD009.htm