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This application outlines Control of Blood Pressure - Afterload
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Afterload is the pressure against which the heart must work to eject blood during systole (systolic pressure). The lower the afterload, the more blood the heart will eject with each contraction.
Like contractility, changes in afterload will raise or lower the Starling curve relating stroke volume index to LAP.
The effect of afterload on stroke colume is due to the fact that the maximum pressure that the heart can develop is smaller at lower ventricular volumes.
Therefore, if the systolic pressure is lower, the heart will be able to contract to a smaller volume at the end of systole. This will result in an improved stroke volume.
Conversely, if the systolic pressure is higher, the heart will be unable to contract to as small a vollume at the end of systole and the stroke volume index will be decreased.
