Stroke volume index is the volume of blood pumped by the heart with each beat (in milliliters) divided by the body surface area (square meters). This allows direct comparison of the stroke volume index of large and small patients.
Stroke volume index is determined by three factors:
- Preload: The filling pressure of the heart at the end of diastole.
- Contractility: The inherent vigor of contraction of the heart muscles during systole.
- Afterload: The pressure against which the heart must work to eject blood during systole.
Starling's Law is the relationship between preload and stroke volume .