SIR Paul McCartney is fighting fit after undergoing a secret heart procedure, according to friends.

The former Beatle had a coronary angioplasty in September last year to open blocked arteries.

A friend of the star said yesterday: “It was a routine procedure and Paul is in excellent health. Fans certainly have no need to worry.

“He immediately returned to a busy schedule, performing in Paris and London the following month.

“Anyone who saw him singing with Kylie on Jools Holland’s BBC2 show on New Year’s Eve will know he is back on top form.”

Sir Paul, 65, underwent the procedure at a private hospital after consulting a Harley Street doctor.

He is understood to have grown concerned about heart problems in 2006, and doctors monitored his health.

A coronary angioplasty is usually carried out under local anaesthetic and involves a fine catheter tube through an incision in the groin.

The tube is pushed up into an artery around the heart and a tiny balloon is inflated to widen the artery, allowing better blood flow.

David Beckham’s father, Ted, had the same procedure last year.

The operation comes as Sir Paul continues to battle estranged wife Heather Mills in the divorce courts. They split in 2006, after four years of marriage, but have failed to reach a settlement over the musician’s £800m fortune and custody of their daughter Beatrice, four.