SAN ANTONIO -

Like many woman in San Antonio, Bonnie Lundy Kwan has a fairly routine workout regiment, but Kwan’s purpose is not routine. 

The 41-year-old is keeping her heart fit -- a heart she was given when she was 21.

Bonnie Lundy Kwan is a heart transplant patient.

That is the motivation to keep it in the best shape possible, she said.

“You don’t get a heart so you can sit on the couch. You get a heart so you can start living,” Kwan said.

She is not only living but defying odds every day. 

Thursday marked the 20th anniversary of her heart transplant. She credits her workout with her longevity.

“I am alive now because I have taken care of my heart through exercise and eating well,” Kwan said.

"I remember her when she first started -- when she first had the transplant. I can’t even tell you the difference," said Carole Morris, Kwan’s trainer.

There are fewer than 200 heart transplant patients world-wide who have lived to see 20 years, so this is a milestone for Kwan.

"I thought I was rocking when I hit seven years. I thought I defied all the odds,” Kwan said.

At first, her body rejected the heart and was in the hospital four months before doctors finally got her body to accept her new heart.

"She was so complicated, they wrote about her," said Dr. Michael Kwan.

Kwan is a transplant surgeon with the Texas Transplant Physician Group.

Kwan is not only a cardiologist, but he is also Bonnie’s husband. He met her after the transplant. 

They were married four years ago -- 16 years to the day after her transplant.

“She is just incredible in every way,” said Kwan. "I think she's done a lot to break the stereotypes of what a transplant patient is and what a transplant patient is not."

Bonnie’s donor, Shay Ledbetter, was 22 at the time. Kwan named her nonprofit in Shay’s honor and helps transplant recipients stay in shape to take advantage of their second chance.

She is also very close to the family. Her dad and donor father walked her down the isle and her donor mom lit the unity candle.

So Bonnie has a reason to be thankful for life and wedded bliss, and always thinks about the reason.

“I think about her every day. Actually, you can’t get a gift like this and not think  about who gave it to you," said Kwan.