How can the heart stay alive during heart surgery?

It varies.. Depending on the operation, different strategies are employed to make sure the heart's metabolic demands are met. Sometimes the heart is kept beating with its normal blood supply. Sometimes the heart is stopped temporarily and cooled so it doesn't need as much oxygen. In these situation, some oxygen can still be delivered to the heart through it's arteries or veins.

Related Questions

Can increased heart rate sometimes during the day cause mitral valve leakage? Had mitral valve heart surgery three months ago.

Mitral regurgitation. Mitral valve leakage, referred to as mitral regurgitation, is a steady state and doesn't come and go but can fluctuate in intensity under certain circumstances. It can cause disturbances in the heart rhythm and cause the heart to race.