American Association of Critical-Care Nurses (AACN) Certification Practice Test

What is the relationship between preload and ventricular filling?

1. Inversely related; as preload increases, ventricular filling decreases

2. Directly related; as preload increases, ventricular filling increases

3. Unrelated factors

4. Varies based on heart rate

The correct answer is: Directly related; as preload increases, ventricular filling increases

Preload refers to the degree of stretch of the heart muscle at the end of diastole, representing the volume of blood in the ventricles just before contraction. This relationship is essential in understanding how the heart functions during various physiological conditions. When preload increases, it typically means that there is more blood returning to the heart, resulting in greater filling of the ventricles. The heart muscle responds to this increased volume—up to a physiological limit—by stretching more, which enhances its contraction force due to the Frank-Starling mechanism. Thus, as preload increases, the volume of blood that fills the ventricles also increases, leading to greater ventricular filling. This relationship is crucial for maintaining adequate cardiac output during varying levels of physical activity and fluid status in the body. It underpins why adequate venous return and preload are vital for optimal cardiovascular function and why it is a significant consideration in clinical assessments and treatments for heart-related conditions.