Final Answer:
A decrease in preload results in B. Decrease in cardiac output.
Step-by-step explanation:
When preload decreases, it results in a decrease in the amount of blood returning to the heart during diastole. Preload is the initial stretching of the heart muscle fibers before contraction, and it directly influences stroke volume—the amount of blood ejected with each heartbeat. According to the Frank-Starling law of the heart, an increase in preload leads to an increase in stroke volume. Conversely, a decrease in preload results in a reduced stretch of the heart muscle fibers, leading to a decrease in stroke volume.
The relationship between preload, stroke volume, and cardiac output can be explained through the equation:
Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)
As preload decreases, stroke volume diminishes. Since cardiac output is the product of heart rate and stroke volume, a decrease in stroke volume will consequently lead to a decrease in cardiac output. This is critical in understanding cardiovascular physiology, as cardiac output is a key determinant of overall blood flow to the body's tissues and organs.
Therefore, a decrease in preload ultimately results in a decrease in cardiac output, making option B the correct answer. This concept is fundamental in the study of cardiovascular dynamics and plays a crucial role in the understanding and management of various cardiac conditions.