Stroke Volume

Stroke volume is the volume of blood pumped out of the left ventricle during systole (the contraction phase of the heartbeat).

It is a core component of cardiac output, which is calculated as:

[ \text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate} ]

A typical adult has a stroke volume of 60–100 mL per beat, with an average of 70 mL.¹

📏 How stroke volume is calculated

Stroke volume is determined by the difference between two ventricular volumes:

[ \text{Stroke Volume} = \text{End-Diastolic Volume (EDV)} - \text{End-Systolic Volume (ESV)} ]

• EDV: Blood in the ventricle after filling (diastole)
• ESV: Blood left after contraction (systole)
  National Center for Biotechnology Information Quizlet

🔧 What determines stroke volume

Stroke volume is shaped by three major physiological factors:

• Preload — the stretch of the ventricle before contraction; higher preload increases stroke volume. Fiveable
• Contractility — the strength of the heart’s contraction; stronger contractions increase stroke volume. Fiveable
• Afterload — the resistance the heart must pump against; higher afterload decreases stroke volume. Fiveable

These three factors interact through the Frank–Starling mechanism, where increased filling leads to stronger contractions. Fiveable

🧠 Why stroke volume matters

Stroke volume is essential for understanding:

• Cardiac output and overall circulatory efficiency
• Heart failure assessment, including ejection fraction (EF = SV/EDV) National Center for Biotechnology Information
• Exercise physiology, where stroke volume rises to meet oxygen demand
• Critical care, where it helps assess perfusion and hemodynamic stability

If you'd like, I can also break down cardiac output, ejection fraction, or how exercise affects stroke volume.

References

1. Bruss ZS, Raja A. Physiology, Stroke Volume. [Updated 2022 Sep 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547686/?redirect=false&utm_source=copilot.com. National Center for Biotechnology Information