Final answer:
Heart failure is a chronic condition in which the cardiac muscle cells lose their pumping strength, leading to inadequate oxygen supply.
Step-by-step explanation:
Heart failure is a chronic condition in which the cardiac muscle cells lose their pumping strength. This means that the heart can't pump with sufficient force to transport oxygenated blood to all the vital organs. The weakened pumping action of the heart impairs the flow of oxygen to the tissues, resulting in inadequate oxygen supply.