Randy Travis had heart surgery on Monday following his admission to a Texas hospital
the previous day in critical condition, his sister-in-law tells PEOPLE.
"We have been told he has had surgery," Teresa Traywick, the wife of Randy's brother Ricky Traywick, said. "Our prayers are going out to him because my husband just had a heart attack last year, so it is in their family."
The Grammy-winning country singer, 54, born Randy Traywick, is "suffering from complications of recently acquired viral cardiomyopathy," a rep has said. Viral cardiomyopathy is a weakening of the heart muscles due to infection.
"Their mother passed away at an early age with her heart, so it is like these boys are following right in their footsteps," Teresa Traywick said. "My prayers are with them. That's all I can say right now."
Travis had been scheduled to play the Deadwood Mountain Grand in Deadwood, S.D., on Wednesday, but that show has been cancelled.
Meanwhile, friends and fans have been offering messages of support.
"Sending a get well message out to my buddy @randytravis tonight. Thinking of you and wishing you a speedy recovery," singer Tracy Lawrence wrote on Twitter.
Added Lance Armstrong
: "Thoughts go out to @randytravis. Heal up soon my man! One of country music's greatest voices ever."
Reporting by ALICIA DENNIS and PATRICK GOMEZ