The Dallas Morning News quoted Michael Mack, director of cardiovascular disease at the Baylor Health Care System in Dallas, as saying the 54-year-old singer, while still critical, is stable and "has shown signs of improvement" since being admitted Sunday.
The country music star last month completed his court-ordered rehab stemming from a 2012 drunken driving arrest and was touring again when he was struck down by pneumonia, which led to complications of viral cardiomyopathy.
He was airlifted Sunday to the hospital and his publicist told People.com Travis Tuesday "underwent placement of an Impella peripheral left ventricular assist device for stabilization prior to transferring hospitals."
Travis' planned concert at South Dakota's Deadwood Mountain Grand Wednesday has been canceled.
2014: The Year in Music [PHOTOS]