Which of the following conditions might be indicated by a reduced LVEF?

A reduced left ventricular ejection fraction (LVEF) is a significant clinical finding that indicates the heart's diminished ability to pump blood effectively. Heart failure can arise from various underlying conditions, but it is frequently associated with a reduced LVEF. In heart failure, the heart may be unable to maintain adequate blood flow to meet the body's needs, which can manifest as symptoms like fatigue, shortness of breath, and fluid retention.

In contrast, hypertrophic cardiomyopathy typically involves a normal or increased LVEF due to the thickening of heart muscle, which may not directly correlate with reduced pump function, especially in mild cases. The normal physiological response to exercise would not lead to a reduced LVEF; in fact, exercise can improve cardiac performance due to increased contractility. While coronary artery stenosis can lead to various issues, its direct effect on LVEF can vary widely depending on the severity and how well the heart compensates for reduced blood flow.

Thus, C—heart failure—is the condition most clearly indicated by a reduced LVEF, highlighting the heart's compromised function in maintaining adequate circulation.