Narrowing of aortic valve in aortic valve stenosis

In aortic valve stenosis, the aortic valve opening is narrowed (top row). The narrowing requires increased pressure within the heart to pump blood across a smaller opening. Eventually this reduces the heart's ability to pump blood to the body. This is similar to attaching smaller and smaller nozzles to the end of a garden hose (bottom row). The narrowing from the nozzle slows the forward flow of water and results in pressure buildup within the garden hose.