Increasing end-diastolic volume alone (inotropicity & afterload held constant) (Figure 2.05A) as in aortic regurgitation, venoconstriction, increased blood volume, etc., augments stroke volume. The area of the pressure-volume loop is increased (increased stroke work), but end-systolic volume always returns to the same point on the isovolumic pressure line, which is generated by momentarily cross-clamping the aorta.
Increasing afterload alone (inotropicity & preload held constant) (Figure 2.05B) as in aortic stenosis or vasoconstriction, depresses stroke volume. Because end-systolic volume increases, loop area and stroke work remain constant although end-systolic pressure increases. A single isovolumic pressure line is defined.
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