Ex-Wales rugby international Rhys Thomas is to undergo heart surgery in preparation for a transplant.
The ex-Scarlets and Dragons player undergoes surgery in Birmingham on Tuesday, 2 September.
Seven-time capped prop Thomas, 32, retired from rugby in 2012 after collapsing during Scarlets training.
"I can confirm he is having an operation today to prepare him for a heart transplant in the near future," said his agent Christian Abt.
Thomas underwent surgery in 2012 after being taken ill during a training session at Parc y Scarlets and announced his retirement from the sport later the same year.
The news prompted former team-mates to send messages of support on social media.
Scarlets and Wales centre Scott Williams tweeted: "All the best with the op."
Racing Metro's Wales scrum-half Mike Phillips said on Twitter: "All the best mate!".
And Dragons number eight Andy Powell tweeted: "Hope everything goes well."
|Rhys Thomas Fact File|
|Born: 31 July 1982 in Johannesburg|
|Wales caps: Seven. Debut: v. Argentina in Buenos Aires, 2006.|
|Clubs/Regions: Newport, Dragons, Scarlets.|
|Did you know? Thomas attended King Edward VII School in Johannesburg along with South African rugby players Joe van Niekerk and Bryan Habana.|
Among those to post similar messages were Wales centre Jamie Roberts, Dragons lock Ian Gough, Worcester forward Jonathan Thomas, Bath prop Paul James, and ex-Wales centre Matthew Watkins.
South Africa-born tight-head Thomas, a former schoolmate of Springbok winger Bryan Habana, won seven Wales caps between 2006 and 2009.
In November 2006, his career with Newport Gwent Dragons was disrupted by what was subsequently described as a "mystery" chest problem.
He had begun his professional career in Wales, making his debut for Newport, the town of his father's birth, in 2003.
He came through the youth ranks at Rodney Parade and made a try-scoring debut for the Dragons following the advent of regional rugby in a 27-5 win over Glasgow in October 2003, before establishing himself as a Dragons regular in the 2004-05 season as the team finished fourth in the Celtic League.
The tight-head made his international debut in Wales' 45-27 defeat by Argentina in Buenos Aires in June 2006, replacing Adam Jones in the second half.
He joined Scarlets from the Dragons in 2009 after making 119 appearances for the Newport-based region.
Thomas scored nine tries in 52 Scarlets appearances and scored four times in his 17 games in his final season.