Wednesday’s Guardian newspaper quoted the aide as saying that the news was not made public for fear it would “creat panic”.
"Although he has had a slight heart attack, the doctors say he will make a full recovery. He is in full control. There is nothing to worry about," the aide, who did not wish to be named, told the London-based paper.
The official added that the news would “have created panic at a critical time when Israelis are threatening Arafat’s life”.
Health 'not a factor'
Israeli officials said Arafat's health was not a factor as the government considered whether or not to carry out its threat to "remove" the 74-year-old Palestinian leader, who has appeared pale in recent days.
"It would be very convenient if nature were to take its course," Jonathan Peled, an Israeli foreign ministry official said.
"But Mr Arafat is a cat with nine lives and we do not believe he has used all of them yet."
Arafat would most likely travel to Egypt or Jordan if he requires medical treatment not available in Ram Allah. But it is unlikely he would leave unless Israel guarantees his return to the West Bank.
Peled told the daily that the Israeli government would be happy to see Arafat leave, but was unlikely to allow him to return.
The Israeli security cabinet approved in principle Arafat's removal on 11 September, two days after twin resistance attacks in occupied Jerusalem and Tel Aviv.
The decision prompted outrage among Palestinians and international condemnation.