Which of the following would decrease stroke volume?

Decreased stroke volume refers to a reduction in the amount of blood ejected by the heart with each contraction. The primary factor influencing stroke volume is venous return, which is the volume of blood returning to the heart. When venous return decreases, there is less blood available in the heart for the ventricles to pump out, leading to a lower stroke volume.

In this context, decreased venous return can occur for various reasons, such as blood loss, dehydration, or conditions that affect blood volume and pressure. Consequently, with less blood filling the heart, the ventricles have a smaller preload (the initial stretching of the heart muscle), which directly impacts the stroke volume according to the Frank-Starling law of the heart.

This law states that an increase in the volume of blood filling the heart leads to a more forceful contraction, while a decrease in this volume results in a weaker contraction. Therefore, in situations where there is diminished venous return, stroke volume inevitably decreases due to reduced preload.

In contrast, a positive inotropic agent would enhance the force of cardiac contractions, thus increasing stroke volume. Systemic vasodilation can impact afterload and potentially increase stroke volume depending on the context, while increased venous return generally raises stroke volume as