Grant Wahl died after an undetected aortic aneurysm ruptured, the American journalist's wife Dr. Celine Gounder has revealed.

The 49-year-old collapsed in his seat while reporting on last Friday's World Cup quarter-final between Argentina and the Netherlands at Lusail Stadium.

Wahl was attended by medics inside the ground and taken to hospital, but his death was later announced and an outpouring of tributes soon followed.

He was flown back to New York City on Monday, and an autopsy revealed the cause of his death, with wife Gounder ruling out any sort of foul play.

"Grant died from the rupture of a slowly growing, undetected ascending aortic aneurysm with hemopericardium," Gounder posted on her husband's blog. 

"The chest pressure he experienced shortly before his death may have represented the initial symptoms. No amount of CPR or shocks would have saved him. 

"His death was unrelated to COVID. His death was unrelated to vaccination status. There was nothing nefarious about his death."

Wahl, who was best known for his long career with Sports Illustrated, attended a medical clinic at Qatar 2022's Main Media Centre four days prior to his death after feeling unwell and was diagnosed with bronchitis.

The much-respected reporter was at the centre of controversy earlier in the World Cup when he sported a rainbow t-shirt in support of LGBT rights as he attempted to attend a match.

He was initially prevented from entering Ahmad bin Ali Stadium for the United States' group game against Wales, although he was later allowed inside.

Wahl's brother suggested he had been "killed" in the immediate aftermath of his death, but he later said he "regretted" those comments and no longer believed that to be true ahead of Wednesday's announcement.

Paying her own respects to her husband, Gounder said: "We will forever cherish the gift of his life; to share his company was our greatest love and source of joy.

"Grant was an incredibly empathetic, dedicated and loving husband, brother, uncle and son, who was our greatest team-mate and fan. 

"While the world knew Grant as a great journalist, we knew him as a man who approached the world with openness and love."