Which physiologic change increases cardiac work but does not enhance cardiac output?
A) Increased preload
B) Increased heart rate
C) Increased contractility
D) Increased afterload

Question

Quizplus · Accepted Answer

A major determinant of stroke volume is afterload,which refers to the impedance or resistance that must be overcome to eject blood from the chamber.The workload imposed on the heart chambers by preload is sometimes called the volume work of the heart.An increase in preload increases the volume work of the heart which must be met by increased oxygen uptake to maintain adequate ATP production.An increase in heart rate results in an increase in cardiac output.However,the increased heart rate is undermined by impaired pumping efficiency.Contractility is independent of fiber end-diastolic length and is therefore not affected by preload.

Which Physiologic Change Increases Cardiac Work but Does Not Enhance