Cardiac output depends on two factors heart rate and stroke volume.

Additional Information

Cardiac output is the volume of blood ejected by each ventricle per minute. This varies from about 5 l/min at rest to around 25 l/min during strenuous exercise. Note that the blood volume of an adult is between 4 and 6 litres. This means that the heart ejects a volume of blood equivalent to the total blood volume every minute.

Heart rate is the number of beats per minute - normally 70 beats/min though the heart rate may be increased up to a maximum of around 200 beats/min during strenuous exercise. Usually the maximum heart rate may be estimated from 220-age (years) beats per min.

Stroke volume is the volume of blood ejected by each ventricle per beat. At rest this is approximately 70-80 ml though during exercise it may increase to 145-180 ml . It should be noted that the ventricles only eject a proportion (50-75%) of their contents with each beat. At rest the volume of blood in each ventricle at the end of filling is 130 ml (end diastole volume) and the volume after ejection is about 50 ml (end systolic volume).