09/14/2012 12:14 pm ET

Leroy Haynes' Artificial Heart First Successful Implant In Illinois History (VIDEO)

A 64-year-old Illinois man left the hospital Thursday without a human heart in his body, but very much alive.

Leroy Haynes, a retired letter carrier from Monee, Ill., walked out of Advocate Christ Medical Center on Thursday after more than three months of treatment for end-stage heart failure, Fox Chicago reports.

Replacing Haynes' failing human heart is a completely artificial device powered by a portable pneumatic pump, a major advance that allows Haynes to live comfortably at home, the Chicago Sun-Times reports. He previously had an implanted battery-powered pump that supported his weak heart, but is now the first Illinois resident to have an entirely artificial device.

Haynes is one of around 50 people in the country living with so-called "freedom drivers": artificial hearts powered by external pumps in small backpacks that allow unprecedented mobility, according to ABC Chicago. The device, which has a distinctive sound similar to a train passing, will buy him a few years while waits on a waiting list for a donor heart.

"It feels different," Haynes said at a press conference, according to CBS Chicago, "but I’m alive."