Speaking on The X Factor tonight (October 20), Arthur said that he felt "dizzy" before and after performing live on the show last week.
After coming off stage, an ambulance was called for Arthur, who was revealed to be experiencing a panic attack. After explaining that he had suffered from pains and that he believed he might be having a heart attack, Arthur said: "I thought I was going to die."
The 24-year-old singer performed LMFAO's 'Sexy and I Know It' for this week's theme, Club Classics.
Arthur won praise from the judges, and Gary Barlow called his rendition of the song "the performance of the series so far".
Reacting to Barlow's comments, Arthur said: "Thanks Gary. That's amazing. Coming from you, that's awesome."
Watch James Arthur perform 'Sexy and I Know It' on The X Factor below:
Photo gallery - The X Factor Club Classics Week:
Copyright: Ken McKay/Thames/Rex Features