Milan: Former controversial Italian Prime Minister Silvio Berlusconi will undergo heart surgery next week for a defective aortic valve, his doctor has said. "A series of cardiovascular checks enabled us to identify a severe aortic insufficiency," Berlusconi's personal physician Alberto Zangrillo told reporters in Milan on Thursday. "There is only one way to correct this -- to substitute the aortic valve. Berlusconi's life was in danger, he risked dying," Zangrillo stated, adding that the 79-year-old had accepted his diagnosis "with great courage and determination". At least 10 percent of patients with disease of the aortic valve die within a year unless they are operated on, Zangrillo stated. He said the operation will last around four hours and will be performed by Ottavio Alfieri, a heart surgeon at Milan's San Raffaele hospital, where Berlusconi was admitted earlier this week. Berlusconi will then spend a couple of days in intensive care before being transferred to a ward to undergo rehabilitation for about a month, Zangrillo said. The billionaire media mogul was hospitalised on Tuesday with 'cardiac deficiency' after feeling unwell at the weekend. Berlusconi had a pacemaker fitted in a hospital in the US when he was 70. The leader of Italy's centre-right, Berlusconi has held the office of, a record four times, the last being from May 2008 to November 2011, but his political influence has declined since he left government.