Yet his aides carefully maintain the impression that he remains in charge, making personnel appointments, issuing statements and signing decrees. Last Saturday, for example, his press service published a telegram that he had sent to the citizens of Tula, a city south of Moscow celebrating its 850th anniversary.
"Tula guns, samovars, cakes, steelware and powerful modern weapons are famous not only in the country but all over the world. The city is lit up with the flame of blast furnaces and the undying spiritual light of Yasnaya Polyana," the President wrote, referring to Leo Tolstoy's estate, which is in the region.
There is more to the telegram than meets the eye, for Tula recently turned into a battleground between two rival Kremlin factions. Mr Yeltsin sent the message after his former friend and presidential security service chief, Alexander Korzhakov, whom he sacked last June, announced plans to run for parliament in a Tula by-election.
The seat fell vacant after Alexander Lebed resigned it to take up the posts of national security adviser and secretary of Russia's Security Council last June. Mr Lebed later teamed up with Mr Korzhakov, and the two men visited Tula last Sunday. However, anti-Lebed forces in the Kremlin were alarmed at the Lebed-Korzhakov alliance (the former a popular former army general, the latter a hawkish ex-KGB officer) and this week they brought about Mr Lebed's dismissal.
The anti-Lebedites are led by Mr Yeltsin's administrative chief of staff, Anatoly Chubais, and the Prime Minister, Viktor Chernomyrdin, and include the President's daughter, Tatyana Dyachenko, and the hardline Interior Minister, Anatoly Kulikov. The first three clearly have Mr Yeltsin's ear at present and may have persuaded him to sack Mr Lebed against his better judgement.
"Yeltsin's entourage surely forced this decision on him," said Alexander Rahr, a German foreign policy specialist. "Yeltsin has rarely made a political mistake, and this seems to be a very big political mistake."
If so, it may be that Mr Yeltsin's heart condition has seriously sapped his ability to exercise authority. Mr Kulikov said on television last Wednesday: "The President's working regime does not permit him to see people every day. I have a schedule, for instance, and according to this schedule I have to see the President in the next five or six days."
A Moscow radio station said Mr Yeltsin's heart specialists thought there was only a 40 per cent chance that he would undergo an operation. It quoted staff at the Yevgeny Chazov Cardiological Centre as saying that his blood had an extremely low level of haemoglobin, and doctors had been unable to raise it to normal.
Lyudmila Telen, a Russian political commentator, said the main consequence of Mr Yeltsin's illness is that "at the moment, all members of Russia's state hierarchy are trying to swallow up as much power as they think they need".