Seventeen-year-old Nicholas McDonald has left his family and mentor Louis Walsh worried ahead of The X Factor final this weekend, due to a rare heart condition.

The Scottish singer suffers from Long QT syndrome, and has spoken in the past about how he needs to take medication daily to slow his heart rate down. Walsh told The Sun newspaper:

"I am worried about the stress and strain on Nicholas. He has this serious heart ­condition. I worry about that for the weekend.

"There is nothing we can do. He is working really hard, we are just going to give him some time off. I think his family are worried but we want him there in the final."

Nicholas has had one incident in the past while playing football, in which he swallowed his tongue and was only saved thanks to his coach, who had to knock two teeth out to clear his air way.

When asked how serious it could be, the judge said: "You just don’t know. When ­somebody dies they’re dead."

Earlier today, Pressparty reported that the X Factor winner will support Beyoncé on her UK tour next year.

Watch Nicholas Mcdonald's first X Factor audition below: