What is the primary consequence of decreased preload on the heart?

Decreased preload, which refers to the lower amount of blood filling the ventricles of the heart during diastole, directly impacts stroke volume, the amount of blood ejected with each heartbeat. When preload diminishes, the heart receives less blood to work with, resulting in a reduced stretching of the ventricular walls, which leads to a decrease in stroke volume. According to the Frank-Starling Law of the heart, the amount of blood filling the heart (preload) influences how much the heart can contract; less preload means less contractile force, which ultimately results in a smaller volume of blood being pumped out into circulation.

This concept is essential for understanding cardiac function, particularly in conditions such as heart failure or hypovolemia, where preload can be significantly reduced, leading to diminished cardiac output and affecting the overall circulation and oxygen delivery to tissues. Through this mechanism, the importance of preload in maintaining adequate stroke volume and ensuring efficient heart function becomes very clear.