Former Italian prime minister and billionaire Silvio Berlusconi, 79, will undergo heart surgery to replace an aortic valve after suffering an attack his doctor said could have killed him.

"He arrived at the hospital in a severe state, he risked his life, he risked dying and he knew it," Berlusconi's doctor Alberto Zangrillo told a press conference on Thursday, saying the operation would take place by the middle of next week.