Name one common symptom of heart failure.

Shortness of breath, or dyspnea, is a hallmark symptom of heart failure. This occurs because the heart is unable to pump efficiently, leading to fluid buildup in the lungs (pulmonary congestion) and resulting in difficulties with breathing, especially during exertion or when lying flat. Patients often describe a feeling of breathlessness that can be exacerbated by physical activity or position changes. Understanding the physiological mechanisms behind heart failure helps in recognizing this symptom as critical for diagnosis and management.