How does aortic stenosis affect cardiac output?

Aortic stenosis results in the narrowing of the aortic valve, which impedes blood flow from the left ventricle into the aorta during systole. This narrowing increases the resistance to flow, which is referred to as afterload. When afterload is elevated, the heart must work harder to generate enough pressure to eject blood through the narrowed valve.

As the left ventricle encounters this increased afterload, its ability to efficiently pump blood can be compromised. Consequently, the overall cardiac output—defined as the volume of blood the heart pumps per minute—tends to decrease, particularly in severe cases. The heart may initially compensate for this added workload through hypertrophy (thickening of the ventricular walls), but over time, the compensatory mechanisms can falter, leading to reduced cardiac output.

In summary, the relationship between aortic stenosis and cardiac output is characterized by increased afterload affecting the heart's efficiency, ultimately resulting in a decrease in the amount of blood pumped out by the heart.