Final answer:
Distended jugular veins are usually the first clinical indication of right-sided heart failure due to the backlog of blood in the venous system.
Step-by-step explanation:
The question seeks to identify the earliest indicator of right-sided heart failure. Among the options provided, distended jugular veins typically offer the earliest clinical sign of right-sided heart failure.
This occurs because when the right side of the heart fails, it cannot effectively pump blood to the lungs, leading to a backlog of blood in the venous system, which manifests as jugular vein distension.
On the other hand, options like peripheral edema, ascites, and hepatomegaly usually develop later as the condition progresses.
These conditions result from chronic venous congestion that occurs as a consequence of ongoing right heart failure.