I am consulting a doctor for heart failure and aortic valvereplacement. i have a feeling of fluid on the ball of my left foot and my big toe feels a little numb. what could be thereason?

Might be a ganglion: If you notice a localized area of swelling in the ball of the foot, it might be a ganglionic cyst, bursa, or neuroma. Impingement on the nerve can cause numbness. Usually in congestive heart failure, swelling looks more generalized in the feet, ankles and legs. If you press on the swelling, and it leaves a dent, that is fluid retention and might be due to your heart.

See a podiatrist: You need to see a podiatrist to establish the problem. The numbness could be related to the swelling.