Landmark Study Maps the Normal Child Heart From Birth to 18 With MRI

Every day, pediatric cardiologists around the world face a deceptively simple question: is this child’s heart normal? For adults, decades of population imaging studies have produced robust reference tables, so a measurement that falls outside the expected range immediately raises a flag. For children, and especially for children of Chinese descent, the answer has long been murkier. A child’s heart changes dramatically in size, mass, and pumping performance from infancy through adolescence, and without age-appropriate benchmarks, clinicians have been forced to extrapolate from adult data or from small, heterogeneous cohorts. A new study published in BMC Pediatrics by Shilan Li, Jing Zhang, and colleagues at Lanzhou University Second Hospital now provides one of the most detailed answers yet, establishing cardiac magnetic resonance imaging reference values for both ventricles in healthy Chinese children and adolescents aged from three months to eighteen years.

The technique at the center of the study, cardiovascular magnetic resonance, is widely regarded as the gold standard for measuring the heart’s structure and function. Unlike echocardiography, which relies on ultrasound beams that must be angled through the chest wall and can be distorted by poor acoustic windows, cardiac MRI captures the beating heart in full three dimensions. The researchers used a steady-state free precession sequence, often abbreviated SSFP, which produces bright blood pools against darker muscle tissue and allows the borders of the ventricles to be traced with high precision. From these tracings, the team could calculate end-diastolic volume, the amount of blood in each ventricle when it is fully relaxed; end-systolic volume, the amount remaining after contraction; stroke volume, the difference between the two; and ejection fraction, the fraction of blood expelled with each beat. Ventricular mass, essentially the weight of the heart muscle, can also be quantified directly from the images.

Establishing what is normal, however, requires more than sophisticated hardware. It requires a carefully screened cohort of healthy volunteers, and this is where the study makes its most distinctive contribution. The participants were enrolled at a single center in Lanzhou, in northwest China, with a median age of ten years and a range spanning from just three months to eighteen years. Recruiting very young children for MRI is a formidable logistical challenge, because the technique demands that subjects lie motionless inside a noisy magnet for several minutes at a time. Infants and toddlers typically require sedation or careful feeding-and-swaddling protocols, and ethical oversight is correspondingly strict. The study was conducted according to the principles of the Declaration of Helsinki, approved by the hospital’s institutional ethics committee, and written informed consent was obtained from participants or their legal guardians. All data were anonymized before analysis.

The analytical approach deserves particular attention because it shapes how the results will be used in clinics. Rather than reporting a single average value for each measurement, the researchers constructed age-related reference curves using the lambda mu sigma method, often called the LMS method. This statistical framework, originally developed for pediatric growth charts, models three parameters simultaneously: the median of the measurement at each age, the spread around that median, and the skewness of the distribution. The result is a smooth set of percentile curves, analogous to the height and weight charts pediatricians pin to their office walls, against which any individual child’s ventricular volume, mass, or wall thickness can be plotted. Because children’s bodies grow in bursts and at different rates in different tissues, such continuous curves capture physiological change far more faithfully than coarse age brackets alone.

The findings reveal a striking pattern of sex differences that emerges and disappears depending on the parameter and the age group examined. Across the entire cohort, boys showed significantly larger values than girls for the left ventricular long diameter, the anteroposterior diameter of the right atrium, the thickness of the left ventricular free wall, left ventricular mass, right ventricular end-diastolic volume, right ventricular stroke volume, and the indexed right ventricular end-systolic volume. When the researchers restricted their comparison to children aged six to twelve, the last four of these differences persisted, suggesting that the divergence in right ventricular size and pumping output becomes apparent during the early school years. Yet the picture is not uniform: in the youngest group, from birth to six years, and in the oldest group, from twelve to eighteen, biventricular functional reference values showed no statistically significant sex differences at all.

Perhaps the most clinically reassuring result concerns ejection fraction, the single most quoted number in cardiac imaging. For both the left and right ventricles, the age groups were statistically comparable, meaning that the heart’s pumping efficiency remains remarkably stable throughout childhood even as chamber volumes and muscle mass expand several-fold. This stability matters because it gives clinicians a relatively fixed target: a child whose ejection fraction drifts below the expected percentile band is signaling trouble regardless of age. By contrast, absolute volumes and masses must always be interpreted against the age- and sex-specific curves, since a right ventricular volume that is perfectly normal for a sixteen-year-old boy would be alarming in a toddler. The study’s stratified reporting, which presents values across defined age bands as well as continuous percentiles, is designed to support both styles of interpretation.

The right ventricle, in particular, stands to benefit from this new dataset. It is the ventricle most often implicated in congenital heart disease, from tetralogy of Fallot to pulmonary valve disorders, and it is also the chamber whose function is hardest to assess with ultrasound because of its crescent shape and position directly behind the sternum. Conditions such as arrhythmogenic right ventricular cardiomyopathy, a rare but serious disorder in which heart muscle is progressively replaced by fat and fibrous tissue, are diagnosed in part by detecting subtle enlargement of the right ventricle. Without pediatric reference values, distinguishing early disease from normal variation has been one of the most difficult judgment calls in pediatric cardiology. Percentile curves derived from healthy children directly address this gap, giving follow-up protocols a quantitative anchor for deciding when a dilated ventricle truly warrants intervention.

The study also fills a population-specific need. Reference values for cardiac dimensions are known to vary with body size, body composition, ethnicity, and environmental factors, and most existing pediatric MRI norms have been derived from North American or European cohorts. Chinese children have historically been underrepresented in such databases, leaving clinicians in China and in Chinese diaspora communities to apply standards that may not perfectly fit. By enrolling a healthy Chinese pediatric population and reporting both raw and indexed measurements, the Lanzhou team has created a resource that can be cross-referenced against international norms, potentially illuminating how cardiac growth differs across populations and refining the global picture of pediatric cardiovascular development.

Several limitations are worth keeping in view. The cohort was drawn from a single center, which ensures consistent imaging protocols but means the curves may need validation in multicenter samples before being adopted universally. The published version is also an early-release, peer-reviewed accepted manuscript that will be replaced by a final version of record, so some details may be refined. Nevertheless, the core contribution is unlikely to change: a systematically acquired, openly accessible set of biventricular MRI reference values spanning the entire pediatric age range. Because the article is published open access under a Creative Commons license, clinicians and researchers anywhere can consult the full percentile tables without subscription barriers.

The broader significance of the work lies in how it converts a fundamental gap in medical knowledge into a practical tool. Growth charts for height and weight transformed pediatrics in the twentieth century by making deviation from normal visible at a glance. Reference curves for the child’s heart, built from magnetic resonance images of both ventricles, promise a similar transformation for pediatric cardiology in the years ahead. For the family of a child undergoing follow-up after congenital heart surgery, or for the teenager with an incidental finding on a sports screening, the difference between anxiety and reassurance may now rest on a curve drawn from hundreds of healthy hearts, each one imaged, measured, and folded into a map of what a growing heart should look like.

Subject of Research: Cardiac MRI reference values for biventricular structure and function in healthy children aged 0 to 18 years

Article Title: Cardiac magnetic resonance imaging reference values of biventricular structural and functional parameters for children aged 0–18 years

Article References: Li, S., Zhang, X., Wang, J., Tao, J., Guo, R., Zhang, H., Ma, Y., Yue, S., Liu, G., Wang, J., & Zhang, J. (2026). Cardiac magnetic resonance imaging reference values of biventricular structural and functional parameters for children aged 0–18 years. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07718-1

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07718-1

Keywords: cardiac MRI, pediatrics, reference values, biventricular function, SSFP sequence, ventricular volumes, ejection fraction, LMS method, Chinese children, pediatric cardiology, growth charts, congenital heart disease