RCIS Practice Test 2026 – All-in-One Exam Prep

Stroke volume, which is the amount of blood ejected by the heart with each contraction, is significantly affected by preload. Preload refers to the initial stretching of the cardiac muscle fibers before contraction, influenced primarily by the volume of blood returning to the heart during diastole. An increase in preload typically results in a greater stretch of the ventricular walls, allowing for a more forceful contraction due to the Frank-Starling mechanism. This relationship means that as preload increases, so does stroke volume, up to a certain point.

While other factors like afterload, contractility, and heart rate also play important roles in determining stroke volume, they do so in different contexts. Afterload refers to the resistance the heart must overcome to eject blood; increased afterload can reduce stroke volume if the heart cannot compensate effectively. Contractility refers to the intrinsic strength of the heart's contractions; higher contractility enhances stroke volume but is not the baseline measure before contraction like preload is. Heart rate influences overall cardiac output (the product of stroke volume and heart rate), but it does not directly change stroke volume per beat in the same foundational way that preload does. Therefore, preload is the most significant factor affecting stroke volume.