Certified Emergency Nurse (CEN) Test 2025 – 400 Free Practice Questions to Pass the Exam

Preload refers specifically to the degree of stretch of the ventricles of the heart at the end of diastole, just before the heart contracts. This stretch is influenced by the volume of blood returning to the heart, but it is more precisely defined as the pressure within the ventricles that occurs due to this volume of blood.

In the context of cardiac physiology, as the ventricles fill with blood, they stretch to accommodate the incoming volume; the greater the volume, the greater the preload. This relationship is critical because it governs the heart's stroke volume based on the Frank-Starling law, which states that an increase in the volume of blood filling the heart results in a more forceful contraction.

The other choices primarily refer to different concepts in cardiovascular physiology. For example, the pressure in the aorta during systole pertains to afterload, which is the resistance the heart encounters during contraction. Meanwhile, the volume of blood returning to the heart does relate to preload but does not capture the essence of what preload is, which specifically addresses the stretch of the ventricular walls. Therefore, the accurate definition aligns with the understanding that preload is intricately related to the pressure stretching the ventricles.