This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Patients with syncope cannot maintain sufficient cardiac output to meet peripheral perfusion demands. Which of the following BEST describes cardiac output? 
Select and explain. 
A. Cardiac output = end diastolic volume - end systolic volume, B. Cardiac output = hea rate X mean aerial pressure, C. Cardiac output = hea rate X stroke volume, D. Cardiac output = stroke volume X mean aerial pressure
C: Cardiac output = hea rate X stroke volume
Answer: C: Cardiac output = hea rate X stroke volume 
Explanation: Cardiac output = hea rate X stroke volume: is the correct answer. 1st Choice is incorrect: Stroke volume = end diastolic volume - end systolic volume 2nd Choice is incorrect: Double product (estimation of cardiac work) = mean aerial pressure X hea rate 4th Choice is a nonsense distractor Ref: Mohrman D.E., Heller L.J. (2010). Chapter 3. The Hea Pump. In D.E. Mohrman, L.J. Heller (Eds), Cardiovascular Physiology, 7e.