Prince Phillip, the Duke of Edinburgh, was rushed to hospital Friday where he underwent treatment for a blocked coronary artery.
Royal officials said Friday that the 90-year-old prince was airlifted from Sandringham, Queen Elizabeth II's estate in Norfolk, to a cardiac unit in Cambridge for "precautionary tests" after he complained of chest pains.
The Royal Family was gathering at the sprawling estate for the holidays.
The palace refused to confirm if Philip had suffered a heart attack, and instead said the tests showed a blocked coronary artery.
"This was treated successfully by the minimally invasive procedure of coronary stenting," the palace said in a statement. "Prince Philip will remain in hospital under observation for a short period."
A spokeswoman for the palace would not say if other members of the Royal Family were with Philip. A hospital spokeswoman referred all calls to the palace.
Doctors said Philip could have suffered a heart attack, but without more information it was impossible to know for sure.
Stenting involves pushing a balloon into the artery and blowing it up to remove the blockage. A metal sleeve that is fitted over the balloon remains in the artery after the balloon is removed.
Dr. Jonathan Tobis, director of interventional cardiology at UCLA, said coronary stenting is much less invasive than surgery because it is typically done through a catheter method, inserting a balloon down a blocked artery, blowing it up to open the blockage, then putting in a stent to keep the artery wall open.
Tobis said that any procedure carries risks, but advances in coronary medicine over the past 30 years means the procedure can be done "remarkably safely -- even in people in their 90s."
"Nowadays, patients typically go home the next day," Tobis said.
It was uncertain how this family emergency will affect the Royal's plans for the holiday weekend which traditionally includes public appearances at a church service, a televised address from the Queen and a private family lunch.
Philip, who has been married to Queen Elizabeth II since 1947, has been known to enjoy good health throughout his life and rarely misses royal engagements. Upon his 90th birthday in June, he announced plans to cut back his official duties.
Earlier this year the prince cancelled an overnight visit to Italy when came down with a cold in October.
He also spent three days in the hospital in 2008 for treatment of a chest infection.
