What symptom indicates left heart failure?

Frothy sputum is a key symptom that indicates left heart failure, primarily due to pulmonary congestion. In left heart failure, the left ventricle struggles to effectively pump blood out to the body. As a result, blood can back up into the lungs, leading to increased pressure in the pulmonary circulation. This pressure causes fluid to leak from the pulmonary capillaries into the alveoli, resulting in pulmonary edema. The fluid in the lungs can mix with air, producing the characteristic frothy sputum, which is often pink-tinged and is a hallmark sign seen in cases of left heart failure and pulmonary edema.

The other symptoms mentioned do not specifically point to left heart failure. For example, fluid buildup in the extremities, while related to right heart failure, does not directly indicate dysfunction of the left ventricle. Decreased heart rate and increased contractility are more associated with different cardiac conditions rather than being direct indicators of left heart failure.