Dogs have different needs than humans, but all dogs have the same needs.

IAMS Pet food Investigation

 A nine month investigation by PETA has uncovered animal cruelty in the IAMS pet food laboratories.

Armstrong's dog Rex – a 9-month-old yellow Lab who was a gift from the cyclist's fiancée Sheryl Crow – had been born with a leaky heart valve, which gradually made him listless and would inevitably prove fatal. So Armstrong had Rex flown to Colorado State University for open-heart surgery on Aug. 31, a 4 1/2-hour procedure that cost over $10,000.

"He's our family dog," the 7-time Tour de France champ tells PEOPLE. "I didn't want to sit down with the kids and say, 'He's only going to live three more months.'"

Armstrong has three children with his former wife Kristen: son David Luke and twin daughters, Isabelle Rose and Grace Elizabeth.

Said their father: "I was prepared to do whatever it took; I just wanted (Rex) to live."

The operation, performed about 25 times a year at CSU, worked; Rex is taking blood thinners and recuperating between Armstrong's Austin ranch and Crow's California home.

"He's going great," says Armstrong of his dog Rex. "It's wild how dogs and kids recover fast."