Shorter Telomeres Reveal Accelerated Biological Aging in Young Fontan Patients

Birthdays count the years a person has lived, but they reveal surprisingly little about how fast the body itself is wearing down. Biological age, unlike chronological age, reflects the actual condition and function of cells and tissues, shaped by a combination of genetics, lifestyle, environment, and disease. In chronic illnesses such as cancer, kidney disease, and cardiovascular disease, researchers have repeatedly observed signs of aging that appear far earlier than a person’s calendar years would predict. This phenomenon, known as accelerated biological aging, has become one of the most intriguing frontiers in modern medicine, and a new study suggests it may hold critical clues for one of the most complex patient populations in cardiology: children and adults living with a Fontan circulation.

The implications of accelerated biological aging are particularly serious in cardiovascular medicine. In adults with heart failure, markers of accelerated aging have already been linked to worse clinical outcomes. But people born with structural heart defects may also carry an elevated risk of age-related health problems, and until now, few studies had examined whether the biology of aging is measurably altered in these patients from a young age. That gap in knowledge raised an important question: could measuring biological aging help researchers and clinicians better understand the long-term health trajectory of people living with complex congenital heart conditions?

To understand why this question matters, it helps to understand what a Fontan circulation actually is. Some children are born with severe heart defects that leave only one functioning pumping chamber, or ventricle, instead of the usual two. Through a series of surgeries performed in early childhood, surgeons create a new route for blood flow: blood returning from the body travels directly to the lungs without a dedicated ventricle pumping it there, while the single working ventricle sends oxygen-rich blood out to the body. This arrangement, called Fontan circulation, leaves patients living with a fundamentally different system for moving blood through the heart, lungs, and body, one that can impose unique stresses on the circulation over a lifetime.

A team at the Stanford Cardiovascular Institute, led by senior author Sushma Reddy, set out to measure biological aging in this population. The researchers compared 90 children and adults with a Fontan circulation against 59 people with normal heart structure and function. Most participants in the study were adolescents, making the findings especially striking. The work, published in the Journal of the American Heart Association, includes co-first authors Jennifer Woo and Annabelle Grace Binti Vincent, and represents one of the most detailed looks yet at cellular aging markers in young people with single-ventricle heart disease.

The team focused on telomeres, the protective caps found at the ends of chromosomes, the structures that carry our DNA. Telomeres shield genetic material from damage, and they naturally shorten each time a cell divides, which is why their length serves as one of the most widely used markers of biological aging. By measuring telomere length in white blood cells, the researchers discovered that people with Fontan circulation had significantly shorter telomeres than the comparison group, and the differences were apparent even at young ages. In a population made up largely of adolescents and young adults, the presence of a cellular aging signature normally associated with much older bodies points to accelerated biological aging at the molecular level.

The pattern was not uniform across all patients, and the differences carried important clinical signals. Telomere shortening was more pronounced in patients whose right ventricle, rather than the left, served as the main pump sending blood to the body. This detail matters because the right ventricle is not naturally built for the high-pressure job of systemic pumping, and its use in Fontan circulation has long been associated with poorer outcomes. Shorter telomeres were also associated with less favorable measurements of circulation, including a lower volume of blood pumped relative to body size, greater resistance to blood flow through the body’s vessels, and lower oxygen levels in blood returning from the upper body. Together, these connections suggest that a molecular marker of cellular aging tracks with specific, measurable features of how the Fontan circulation functions.

Follow-up measurements added an even more compelling dimension to the findings. When the researchers re-examined patients, typically about a year after the initial assessment, they found that nearly half of the patients who had experienced telomere loss had also accumulated an increase in the number of associated health conditions. By contrast, only about one in five patients whose telomeres remained stable or even lengthened showed a similar growth in their burden of health problems. This link between telomere loss and a mounting burden of medical complications suggests that tracking biological aging over time could offer clinicians an additional window into how a patient’s health is evolving, potentially revealing deterioration before it becomes obvious through conventional measures.

Despite the striking associations, the researchers are careful to emphasize that these findings are a starting point rather than a predictive test for any individual patient. The study could not determine whether telomere shortening actively contributes to health problems or is instead a consequence of them. It also remains unclear whether patients with Fontan circulation were born with shorter telomeres or developed them as a result of their altered circulation over time. Importantly, the study did not establish that telomere length predicts survival or the future need for a heart transplant, and the authors caution against interpreting the results as a forecast of any single patient’s fate.

The next step for the research is to follow changes in telomere length over much longer periods, which will determine whether this cellular marker can provide earlier clues to future health problems in Fontan patients. If the connection is confirmed in longitudinal studies, biological aging could become an additional tool for monitoring patients and refining estimates of their long-term outlook. The work also lays a foundation for investigating whether interventions that influence biological aging, from lifestyle modifications to future therapies, could help slow its effects in this vulnerable population. Such approaches remain speculative for now, but the study opens a door that did not previously exist.

For the growing community of people living with Fontan circulation, many of whom are now reaching adulthood thanks to decades of surgical advances, the goal of this research is to look beyond age in years and understand the changes occurring within the body at a cellular level. If the biology of aging can be measured, tracked, and eventually modified, clinicians may one day be able to intervene earlier, tailor follow-up care more precisely, and ultimately use that knowledge to improve long-term health for patients whose hearts work in fundamentally different ways. The study is a reminder that the passage of time is written not only in calendars, but in the chromosomes of every cell, and that reading that molecular record may transform how medicine cares for its most complex patients.

Subject of Research: Accelerated biological aging measured by telomere length in children and adults with Fontan circulation

Article Title: Biological aging offers clues to long-term health after Fontan surgery

Article References: Biological aging offers clues to long-term health after Fontan surgery. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Fontan circulation, telomeres, biological aging, congenital heart disease, single ventricle, Stanford Cardiovascular Institute, Journal of the American Heart Association, cardiovascular research, right ventricle, health outcomes, white blood cells, pediatric cardiology