What clinical sign might indicate a patient is experiencing heart failure?

Persistent shortness of breath is a clinical sign that may indicate a patient is experiencing heart failure. In heart failure, the heart's ability to pump blood efficiently is compromised, leading to fluid buildup in the lungs (pulmonary congestion) and resulting in difficulty breathing, especially during physical activity or when lying flat. This symptom can be due to the lungs becoming congested with fluid, making it hard for oxygen to be exchanged effectively.

In contrast, the other choices do not relate to typical signs of heart failure. Increased appetite and energy, improved mobility and stamina, and reduced body weight are generally not consistent with heart failure, as patients often experience fatigue, decreased exercise tolerance, and fluid retention. Therefore, persistent shortness of breath is a key indicator that warrants further assessment for heart failure.