When analyzing the pressure-volume loop for decreased venous compliance, would afterload be increased or decreased?
Here is where I am at so far: Decreased venous compliance-->decreased pooling-->greater amount of blood that returns to the heart--> increased filling-->increased preload-->frank-starling mech. activated so contractility increases thus you have an inc. in stroke volume-->increased cardiac output--> higher areterial pressure thus increased afterload.
BUT: When you analyze the pressure-volume loop for decreased venous compliance the end diastolic volume is increased [as it should be] and end systolic volume is decreased [as it should be due to inc. stroke volume cardiac output]---but according to my reasoning afterload should be increased due to inc. cardiac output, because an inc. cardiac output will leave more blood in the artery [aorta] --> inc. aortic pressure --> inc. afterload.
I thought that on a pressure-volume loop diagram afterload-increases are represented by a shift to the RIGHT [meaning end systolic volume (ESV) goes up], but the actual PV-loop diagram for decreased venous compliance has a shift to the LEFT (dec. ESV). I thought that ESV is the single best measure of afterload, i.e and inc. in ESV would indicate an inc. in afterload and a dec. in ESV would indicate a dec. in afterload.?
What's going on or what am I missing??
-Thank you for any help
-Richard
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