Which change would simulate decreased afterload in this model?

Which change would simulate decreased afterload in this model?

• A. Lower pressure in the right beaker
• B. Higher pressure in the right beaker
• C. Lower pressure in the left beaker
• D. Increase left flow tube radius

Answer: (A)

Afterload is the pressure the heart has to push against to eject blood. In this hydraulic model, the load opposing ejection is represented by the pressure in the right-side reservoir. Lowering that reservoir’s pressure reduces the opposing force the ventricle must overcome, so the heart would be working against a smaller afterload. That’s why lowering the pressure in the right beaker best simulates decreased afterload. Raising the pressure in the right beaker would make the ventricle work harder, increasing afterload. Lowering the left-side pressure mainly affects filling or preload rather than the resistance to ejection. Increasing the radius of the left flow path reduces resistance there, but the direct determinant of afterload in this setup is the right-side pressure, so it doesn’t produce the same decrease in afterload.

Afterload is the pressure the heart has to push against to eject blood. In this hydraulic model, the load opposing ejection is represented by the pressure in the right-side reservoir. Lowering that reservoir’s pressure reduces the opposing force the ventricle must overcome, so the heart would be working against a smaller afterload. That’s why lowering the pressure in the right beaker best simulates decreased afterload.

Raising the pressure in the right beaker would make the ventricle work harder, increasing afterload. Lowering the left-side pressure mainly affects filling or preload rather than the resistance to ejection. Increasing the radius of the left flow path reduces resistance there, but the direct determinant of afterload in this setup is the right-side pressure, so it doesn’t produce the same decrease in afterload.