(CNN) More than 20 years ago, Terri Mattula's dog Gator passed out while her husband was walking him.

They took Gator to the vet and learned he had a third-degree heart block and needed a pacemaker. However, they were both students at the time and couldn't afford one.

"That's urgent arrhythmia," Mattula said. "If a person had that kind of block, within 24 hours they'd have a pacemaker."

Now a nurse, Mattula -- who has worked in cardiology for about 17 years -- has started a donation program to recycle used pacemakers to help animals like her old friend, Gator.

"I get a lot of arrhythmia patients and there is a large amount of pacemaker work," Mattula said. "Explanted pacemakers are normally thrown away."

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