"We must understand that the person is getting ready for a very serious operation," said Sergei Mironov, head of the presidential health centre. "It needs sufficiently extensive balanced and serious preparations. You all understand what is at stake."
Russian cardiologists and Western consultants, including the pioneering US surgeon Michael DeBakey, will meet on Wednesday to set a date for the bypass, an operation in which veins are grafted on to coronary arteries to improve the flow of blood to the heart.
Renat Akchurin, the Russian surgeon who is most likely to lead the operation, said much depended on the overall strength of the patient. "Success rates are about 98 per cent if you are dealing with an uncomplicated generally healthy patient." But he added: "If you have some problems with other systems and organs, the percentage of success might decrease to 90 per cent."
Dr Mironov admitted that his heart was not all that troubled Mr Yeltsin. "All of us during our lives acquire quite a lot of different problems with our organs and unfortunately Boris Nikolayevich has them too," he said.
Mr Yeltsin has moved to stop any power struggle in his absence by declaring that his prime minister, Viktor Chernomyrdin, will be acting president with control over the nuclear button while he is incapacitated.