What would other doctors do if the doctor performing surgery has a heart attack?  

I think that they would rush the doctor out of the surgery room, and get other doctors tot end to him or her. Then the remaining doctors would tend to the patient. If there was no doctor to tend to the patient, I am not sure what would happen. I suppose they'd have to stop the surgery and close the patient up or keep watch of their vitals.

thats the reason why the doctor have an assistant doctor with him during operation for this kind of incident as if the main doctor suffered heart attack the assistant can immediately continue with the operation while the main doctor is being rush to emergency. before i undergo operation my doctor introduce me to his assistant doctor so that i know that theres 2 doctor with me during operation.

I agree with the other respondants. Surgeons usually have assistants at the table with them...they don't need to stick around to do the closing for instance. If the surgeon had a heart attack someone on the team would call a code and help would arrive to care for the doctor. Another surgeon would then take over.