A heart from the Harts
Harts siblings’ lives forever changed, thanks to UF Health Congenital Heart Center
Feb. 2, 2026 — Aubree and Londyn Harts sit in their living room and show off their souvenirs. Aubree, 11, holds a cannula from a Berlin Heart — an external device that helps children who are experiencing heart failure and are awaiting a transplant. Londyn, 10, grips a leadless pacemaker — a leading-edge device that represents breakthroughs in lifesaving pacemaker technology.
Aubree (left) and Londyn Harts (right) holding the pieces of medical equipment that saved their lives
While today, the sisters play and laugh like any other children their age, returning to a sense of normalcy took time, hope and a lot of heart.
A difficult phone call
It all started in 2023 when their mother, Julia Jackson, received a call from Aubree’s daycare, asking her to be picked up because she’d been sick.
“We took her to a walk-in clinic, and they said she probably had a stomach bug or was dehydrated,” Jackson said.
But it wasn’t a stomach bug and it wasn’t dehydration. Careful testing made it clear there was something wrong with Aubree’s heart. As the seriousness of the situation became apparent, Aubree was flown from Lakeland to Orlando, then from Orlando to UF Health Shands Children’s Hospital in Gainesville.
“I didn’t know anything about Shands other than coming as a kid, but they said that’s where the best doctors are, and they sent us,” Jackson said.
The health care team at UF Health Shands explained to Jackson that Aubree had cardiomyopathy, a chronic heart disease that — in her case — would necessitate a heart transplant. She would need to spend several months with a Berlin Heart while on the waitlist.
Jackson decided to move with her daughters from Tampa to Gainesville while they waited for a new heart for the 9-year-old.
Support every step of the way
Being hospitalized with a medical emergency like Aubree’s can be a terrifying experience for young patients and their families, but Jackson said the care teams at UF Health Shands — comprised of a multidisciplinary team from physicians in pediatric cardiology, surgery, critical care medicine and beyond — made her feel safe.
“Everybody was so nice, empathetic and welcoming,” she said. “They went above and beyond.”
Julia holds her daughter Londyn.
Mark Bleiweis, M.D., the William G. Lassiter Jr. and Aneice R. Lassiter Professor and director of the UF Health Congenital Heart Center, was Aubree’s transplant surgeon. He explained her situation to the family, including the difficult news that Aubree would need a heart transplant and the specifics of waiting for a donor organ to become available.
“I totally believed in him,” Jackson said. “I’m a praying woman, so I prayed about it and felt totally at ease that he was the right person for the job.”
Bleiweis said the connections his teams form with families are one of the most special things about practicing medicine at the Congenital Heart Center.
“Every family who walks through our doors places an extraordinary amount of trust in our team,” Bleiweis said. “Being able to provide the level of specialized care these children need, while supporting parents every step of the way, is something we never take for granted.”
Aubree was placed on a Berlin Heart in January 2023, keeping her stable until a successful heart transplant that April. Today, thanks to Aubree’s dedicated care teams at UF Health, 11-year-old is back to doing the things she loves with her sister: watching movies, playing board games and creating videos.
Londyn’s journey
A little over two years later, in September 2025, Jackson received another alarming call from school.
This time, Londyn was sick. The 10-year-old was unable to stay awake, and her eyes were rolling back in her head.
“I took her straight to the emergency room and called Ms. Jen in tears,” Jackson said. “She had me put her on speaker phone, and she and the ER nurse spoke to each other. When I got back on the phone, all she said was ‘OK, we got you.’ That was all I needed to hear.”
“Ms. Jen” is Jennifer Rackley, APRN, a pediatric nurse practitioner. She’d interacted with Jackson during Aubree’s visits to the hospital two years earlier and had built a strong rapport with the family.
“It’s about trust,” said Rackley, who has worked at UF Health Shands for more than 20 years. “You go through some of the worst days with these families. You build relationships with them and you’re on a journey with them. It’s an honor.”
Just like her sister, Londyn ended up with the care team on 10-2, the UF Health Shands pediatric intensive care unit. And just like her sister, Londyn was diagnosed with cardiomyopathy.
Thankfully, Londyn wouldn’t need a transplant. Instead, she would need a pacemaker.
“I know several people in the military who have pacemakers, so I wasn’t too worried about the procedure,” said Jackson, a veteran staff sergeant who served in the U.S. Air Force. “What worried me was her age; I don’t know any kids that have gone through this.”
Jackson was right: Londyn was very young to need a pacemaker. She would be making history as the youngest patient in the world — at the time of her procedure — to ever receive a dual-chamber leadless pacemaker.
Aubree and Londyn at the UF Health Congenital Heart Center
“We were the first center in Florida to implant leadless pacemakers in pediatric patients and were the only center implanting dual-chamber leadless devices in young pediatric patients,” said Londyn’s doctor, Mohammad Al-mousily, M.D., a clinical assistant professor at the Congenital Heart Center. “It’s a newer technology and has a lot of advantages over other types of pacemakers, particularly for children.”
Londyn’s special pacemaker consists of two small pill-shaped devices that sit in the top and bottom chambers of her heart. They communicate with each other wirelessly to ensure the chambers of her heart beat in time with one another.
For Londyn, no wires meant a less invasive procedure, a lower risk of infection, an easier and faster recovery process and the opportunity to have a normal life as she grows up.
“What we do is easy compared to what these families are going through,” Al-mousily said. “We have the expertise and equipment and training facilities, but what drives us is seeing how amazing these families are, how much they care and how strong they are.”
‘Heart from the Harts’
The hospital is a scary place for children, whether they’re patients themselves or are visiting loved ones. The care teams on 10-2 know this and make every effort to attend not only to their patients’ physical needs, but also the emotional needs of their families.
“I lived there every day with Aubree,” Jackson said. “The child life specialists were always kind and would make sure I had any resources I needed or answered any questions I have.”
Sarah Meurer, a certified child life specialist at UF Health Shands, worked with both girls during both of their patient experiences on 10-2. Her job is to help patients and families cope with the hospital experience with a mix of guided activities and patient education.
“We do day-to-day activities that help them express their emotions and feelings,” Meurer said. “We also help them understand what’s going on with their bodies. ‘What is a Berlin Heart? Why am I sick? Why do I have to take this medicine?’”
According to Meurer, the most important part of her job is helping the kids normalize their hospital experience. That means giving them opportunities for play and letting them do the kinds of things they’d be doing at home.
“I had so much fun with those girls,” she said. “They’re hilarious and fun; they’re real and authentic.”
To this day, Meurer wears a heart pin on her hospital identification badge — a gift from Aubree and Londyn.
“It’s my heart from the Harts,” she said.
Found family
The girls still have regular check-ins with their care teams, but as they continue their amazing recoveries, the visits are less often than they used to be. That means less time at the hospital and more time living their lives.
No parent wants to go through Jackson’s experience, but every parent wants to ensure their children have the very best care in the very worst moments of their lives.
“I was trying to move away from Gainesville because Aubree was stable,” Jackson said. “I thank God that I didn’t go anywhere, because when Londyn got sick, I knew she would get the same amazing care my other baby got.”
“They’re not doctors or anesthesiologists at this point,” she continued. “They’re the screen savers on my phone. They’re family.”
