Which of the Following Defines Cardiac Output

Question

Which of the following defines cardiac output?
A) Cardiac index ´ ejection fraction
B) Heart rate ´ stroke volume
C) Stroke volume ´ ejection fraction
D) Afterload ´ heart rate

Accepted Answer

Cardiac output is the amount of blood pumped by the heart per minute. It is the product of heart rate (the number of heartbeats per minute) and stroke volume (the volume of blood pumped by the heart per beat). Therefore, choice B, which is heart rate multiplied by stroke volume, best defines cardiac output. The other choices are incorrect because cardiac index is a measure of cardiac output normalized to body surface area, ejection fraction is the percentage of blood ejected from the heart with each beat, and afterload is the load against which the heart has to work to eject blood.