<prompt> Cardiac output varies under different physiological conditions. It is decreased by?Increased hea rateDecreased hea rateIncreased stroke volumeNone of the above  <response>: Cardiac output is the product of the hea rate and stroke volume CO HR x SV. Therefore, cardiac output decreases by bradycardia. Ref: Mohrman D.E., Heller L.J. 2010. Chapter 3. The Hea Pump. In D.E. Mohrman, L.J. Heller Eds, Cardiovascular Physiology, 7e. 