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NASHVILLE, Tennessee (AP) -- Doctors say country music star Randy Travis, 54, was in good health until three weeks before he was hospitalized, and is now in congestive heart failure because of a viral respiratory illness he contracted.

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The information came in a video statement from Drs. William Gray and Michael Mack of the Baylor Health Care System on Wednesday.

Although Travis remains in critical condition, Mack says "his condition has stabilized and he has shown signs of improvement."

On Sunday, the Grammy winner, best known for his hits "Forever and Ever, Amen" and "Three Wooden Crosses," was admitted to a Texas hospital with viral cardiomyopathy, a condition that can lead to heart failure. The cardiomyopathy caused his heart to weaken and enlarge, so it could not pump properly. To assist his heart function, "placement of an IMPELLA peripheral left ventricular assist device," according to his publicist Kirt Webster. Although not common, alcohol and cocaine abuse can cause viral cardiomyopathy.

"Our prayers are going out to him because my husband just had a heart attack last year, so it is in their family," Travis' sister-in-law Teresa Traywick said in a statement via USA Today on July 9. "Their mother passed away at an early age with her heart, so it is like these boys are following right in their footsteps. My prayers are with them. That's all I can say right now."

Travis, who pleaded guilty to a charge of driving while intoxicated in Texas earlier this year, was hospitalized in 2012 after a fight near a church in Plano, Texas.

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