This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
Cardiac output is decreased by 
Select and explain. 
A. Increased Hea rate, B. Decreased Hea rate, C. Increased stroke volume, D. Increased strength of contraction
B: Decreased Hea rate
Answer: B: Decreased Hea rate 
Explanation: The amount of blood pumped out of the hea per beat is the stroke volume, is about 70 mL.The output of the hea per unit of time is the cardiac output cardiac output = stroke voume*hea rate Therefore decrease in hea rate decrease cardiac outputIncrease in either of hea rate or stroke volume or both increase cardiac outputRef: Ganong's Review of Medical Physiology Twenty-Third Edition Page No:514