Which condition involves the heart's inability to pump all returning blood, causing a backup?

Heart failure is a condition characterized by the heart's inability to pump effectively, leading to inadequate blood flow to meet the body's needs. This inefficiency results in a backup of blood in the veins, causing congestion in the lungs and other areas. The heart’s compromised ability to manage the incoming blood volume impacts its function, leading to symptoms such as fatigue, shortness of breath, and fluid retention.

In contrast, other conditions such as a heart attack involve a sudden blockage of blood flow to a part of the heart muscle, which can lead to damage but does not specifically describe the chronic inability to pump blood that characterizes heart failure. Heart block refers to an electrical conduction issue within the heart that can disrupt the heart's rhythm but does not inherently involve the pumping capacity itself. Hematocrit, while a measure of the proportion of blood volume that is occupied by red blood cells, is not related to heart function and, therefore, does not pertain to the heart's ability to pump blood.