Former NFL linebacker and Detroit Lions general manager Matt Millen has undergone a successful heart transplant and is recovering in a New Jersey hospital.

"Doctors said the heart was a perfect match and he is doing well," Millen's wife, Pat, told NBC Sports via text. "The surgery went smoothly."

Before the surgery, Matt Millen told NBC Sports that the transplant was set to begin at 1 a.m. ET and would take up to six hours.

Newark Beth Israel Medical Center confirmed to Outside the Lines that the procedure was performed in its hospital Monday morning.

Millen has been suffering from amyloidosis, a rare disease that necessitated the surgery. In October, Millen stepped away from his work as a broadcaster with the Big Ten Network to focus on his health.

A former ESPN employee, Millen had been in the hospital for nearly three months waiting for a transplant.

Millen, 60, went public about his disease in April, when he told the Morning Call of Allentown, Pennsylvania, that his heart was working at 30 percent of its capacity. Amyloidosis occurs when amyloid, a starchlike protein, builds up in bone marrow and spreads to organs and other body tissue. As it does, it can cause organs to fail. The Mayo Clinic has reported that 70 percent of people diagnosed with amyloidosis are men between the ages of 60 and 70.

A second-round pick by the Raiders out of Penn State in 1980, Millen was a linebacker for 12 seasons in the NFL for Oakland, San Francisco and Washington. He was an All-Pro twice and a Pro Bowler once and won four Super Bowls.

After becoming a broadcaster following his playing days, Millen was hired by the Lions in 2001 to become team president and general manager. Detroit fired Millen in the middle of the 2008 season -- a year that ended with the league's first 0-16 campaign.

Information from ESPN's Michael Rothstein was used in this report.