"It helps me that I can do all of these things. I try to be as active as I can and be a normal teenager with all this stuff going on," Kash said during a checkup at Children's Hospital of Philadelphia this month.
But it hasn't been easy. After a series of surgeries in infancy, survivors like Kash and their families face an uncertain future filled with lurking complications that can include heart and liver damage.
She is part of the hospital's growing Single Ventricle Survivorship Program, the first of its kind. It has attracted more than 300 patients from around the world since it began in 2010. Patients receive care from a team of specialists.
The program exists because thousands of survivors are making it to their 20s and 30s and are often encountering learning disabilities and delays in puberty and growth. They may have difficulty exercising or playing sports.
Patients' abnormal heart rhythms can raise the risk of blood clots and stroke. They can also develop liver abnormalities and protein-losing enteropathy (loss of protein in the stool).
The program "is an idea that derives from and exists in cancer. You're never fully cured of that particular condition," said physician Jack Rychik, director of the Fetal Heart Program and Single Ventricle Survivorship Program at Children's. "The initial goal was to create survival. Now, our next goal is to create a normal quality life and a normal duration of life."
About 3,000 U.S. children are born each year with single ventricle heart defects, and about three-fourths of them now survive.
Infants with this defect undergo a series of three open-heart surgeries - in the first week after birth, around 6 months, and from 18 to 36 months - while surgeons reconfigure the heart and circulatory systems.
The final surgery, called a Fontan procedure, makes the heart work like a one-sided pump with two chambers. The heart no longer receives deoxygenated blood from the veins. Instead, this blood flows directly to the lungs. The heart receives oxygenated blood from the lungs and pumps it to the body.
Jorge Best Reategui, 12, had the surgeries at Children's, and has returned almost yearly from Lima, Peru, with his parents, Carmen and Jorge. At this year's visit, he exercised on a bike so doctors could check his heart rhythm and measure changes in his heart rate.
His mother, Carmen Reategui de Best, couldn't hold back tears when Rychik told her, "He looks great. He's functioning at the top of his class."
The only indication of something different was a scar across Jorge's chest.
"We treat him like a normal boy at home," she said. "We don't know what will happen next. It's very hard and will continue to be hard, but it's worth it. This is proof that it can work."
Rychik advises Jorge's parents that he should get a liver biopsy in the next two years. One surprising concern is congestive liver fibrosis - the accumulation of tough, fibrous scar tissue in the liver - in patients as young as 14.
"The Fontan circulation isn't perfect . . . . In the absence of a pumping chamber, the blood flows passively to the lung and this can cause congestion in the organs, and that congestion can take its toll," Rychik said.
Liver fibrosis is most often without symptoms, but it can lead to permanent and symptomatic liver damage when not treated early, said Elizabeth B. Rand, medical director of the Liver Transplant Program at Children's.
"We treat the liver by treating the heart," she noted. "The idea is that these are not livers that have a primary liver disease, but livers that are suffering from back pressure due to poor blood flow into the lungs."
Cardiologists can relieve that back pressure by improving blood flow to the lungs with a drug such as sildenafil, better known as Viagra, which relaxes the blood vessels in the lungs so blood can flow easier, or by procedures that expand arteries, she said.
In Kash's case, she is part of a small group with protein-losing enteropathy (PLE), which causes inflammation and protein loss. Symptoms include swelling of the abdomen, shin and ankle areas, and a change in bowel habits, along with diarrhea and abdominal discomfort. It needs to be treated and managed.
"Sometimes the PLE comes unexpectedly and rages through my body," Kash said.
She has also had more serious bouts of illness from a compromised immune system.
Kash did fairly well until 2008, when her aortic valve began leaking. In 2010, she had valve replacement surgery at Nemours/Alfred I. duPont Hospital for Children in Wilmington. After the surgery, the PLE became worse, she said.
"Without any protein, you can't grow or have puberty," said Kash, who stands 4 feet, 11 inches and weighs 81 pounds.
Kash takes budesonide to treat the PLE, but her high dosage puts a lot of stress on her body.
Doctors have recommended that Kash receive a heart transplant. This spring, she will get a gastric tube to give her more nutrition and make her a better transplant candidate.
"I always think there is something else that can help her," said Delores Kash, Nina's mother. "I always look forward."
Contact Anna Nguyen at email@example.com. Read her blog on children's health at www.philly.com/healthykids.