Which condition prevents the heart from pumping blood effectively?

Heart failure is a condition in which the heart is unable to pump blood effectively to meet the body's needs, leading to a variety of symptoms and complications. It can result from several underlying issues, such as damage to the heart muscle or impaired function of the heart chambers. In heart failure, the heart may still be beating, but the blood flow is insufficient, causing fatigue, shortness of breath, and fluid retention among other symptoms.

This condition can develop as a result of myocardial infarction (often a heart attack), where a part of the heart muscle is damaged. It can also be influenced by arrhythmias, which are irregular heartbeats that can disrupt effective pumping. Cardiomyopathy, which refers to diseases of the heart muscle itself, can likewise lead to heart failure, as it affects the heart's size, shape, and ability to pump.

In contrast, while the other conditions listed may impact heart function or lead to heart failure, heart failure itself explicitly encapsulates the heart's inability to pump blood effectively, fulfilling the requirement in the question.