Stroke volume

Stroke volume is the amount of blood ejected with each beat of the heart.

Men, on average, have higher stroke volumes than women due to the larger size of their hearts.

Stroke volume can also be increased by long term (aerobic) exercise, which frequently results in a slower heart rate. A slower heart rate allows the ventricles to fill up with more blood, which ultimately allows more blood to be ejected. This decreases the amount of strain placed on the heart.

Equations involving stroke volume:

Stroke Volume x Heart rate = Cardiac output

Stroke Volume = End Diastolic Volume - End Systolic Volume

Instrinsic factors controlling stroke volume include preload. An increase in volume or speed of venous return will increase stroke volume (e.g. exercise, slow heart rate). On the other hand, low venous return (e.g. severe blood loss or rapid heart rate) could decrease stroke volume.

Extrinsic factors controlling stroke volume include afterload. Though not usually affecting stroke volume in healthy individuals, in hypertension, it will hinder the ventricles in ejecting blood. This causes reduced SV.