Stan Larkin survived 555 days without a heart, and was still able to engage in sports.

The 25-year-old young man from Ypsilanti, Michigan went along with his daily activities, looking nothing out of the ordinary.

The only unusual thing about him was that he carried a backpack wherever he went. His bag actually contained a device called SynCardia Freedom Total Artificial Heart, which was pumping life into his body in place of his real heart.

Stan's heart was removed from his body in November 2014. Nine years ago, he collapsed without warning while playing basketball. He was then diagnosed with arrhythmogenic right ventricular dysplasia (ARVD), a condition that causes irregular heartbeats and presents immediate risk of sudden cardiac arrest.

According to a report from Washington Post, the University of Michigan Hospital first hooked him up to SynCardia's "Big Blue," a 418-pound self-regulating air pump for patients waiting for transplant. Eventually, Stan was plugged into a portable version of the "Big Blue," the 13.5-pound SynCardia Freedom portable driver, which comes in a SynCardia-made backpack or shoulder bag. The device is connected to Stan's body beneath the ribcage, and features a display panel that shows the patient's heartbeats per minute, fill volume and cardiac output.

Jonathan Haft, cardiac surgeon at the University of Michigan Hospital, said on a local news site that Stan's artificial heart is working well and that he is completely healthy.

The downside was that he couldn't carry his daughters and would have to be careful in taking baths.

But on the brighter side, he wasn't confined in the hospital and he could even play basketball. He would play pickup basketball, carrying his heart in his backpack around the court.

The heart transplant only happened May of this year, and Stan is recovering from the procedure at the University of Michigan Frankel Cardiovascular Center.

"Most people would be scared to go so long with [an artificial heart], but I just want to tell them that you have to go through the fear, because it helps you," Stan told CNN.

"I'm going home so fast after the transplant because it helped me stay healthy before the transplant," he added.

According to data from the U.S. Organ Procurement and Transplantation Network, there are about 4,000 patients in the U.S. waiting for human heart transplants.