Will continuing to smoke make my heart surgery less successful?

Yes, Definitely: Even stopping a few days prior is helpful because the blood is better at carrying oxygen even shortly after exposure is removed. Cigarette smoking is known to cause arterial disease especially in small arteries. Numerous, well devised studies strongly indicate that wound healing is delayed due to smoking. Not to mention that lung function is disrupted in the immediate post op period anyway.

Yes: Continuing to smoke will limit the long-term patency of any bypass graft. It also will adversely affect your heart function and lung function in general.