Stroke Volume and Heart Rate: The Inverse Relationship

Stroke volume (the amount of blood ejected by the left ventricle per beat) and heart rate (pump rate) share an inverse relationship.

• As heart rate increases, stroke volume decreases. The ventricles have less time to fill with blood during diastole, reducing preload and thus stroke volume.
• As heart rate decreases, stroke volume increases. Longer diastolic filling time allows more complete ventricular filling, increasing preload and stroke volume (up to a physiological limit).

This relationship is a key component of cardiac output regulation (Cardiac Output = Stroke Volume × Heart Rate). The Frank-Starling mechanism also plays a role: increased venous return stretches cardiac muscle fibers, enhancing contractility and stroke volume.