Cardiac Biomarkers in Children With Congenital Heart Disease: A Medical-Legal Guide for Attorneys

Introduction

Few areas of pediatric cardiac litigation generate as much confusion — on both sides of the aisle — as the role of blood tests in children with congenital heart disease (CHD). Three biomarkers dominate the discussion: B-type natriuretic peptide (BNP) and its companion N-terminal pro-B-type natriuretic peptide (NT-proBNP), which reflect cardiac wall stress and strain, and cardiac troponin (troponin T or troponin I), which reflects injury to heart muscle cells.

In adult medicine, these tests have crisp, widely accepted decision thresholds. A troponin above a defined cut-off helps diagnose a heart attack; a BNP above a defined cut-off helps diagnose heart failure. Attorneys who import those adult certainties into a pediatric case — whether to argue that a "missed" biomarker would have saved a child, or to argue that a "normal" biomarker proved the child was fine — are building on sand. In children, and especially in children with structurally abnormal hearts, these tests behave very differently. They are genuinely useful adjuncts, but they are not definitive, their normal ranges shift dramatically with age, and validated pediatric cut-off values largely do not exist.

This white paper explains, in plain language, what these tests do and do not tell us in children with CHD, where they legitimately become litigation targets, and where defense themes are well supported by the medical evidence. It is written for attorneys, insurers, and healthcare organizations evaluating potential pediatric cardiac malpractice claims.

Clinical Vignette

The following scenario is entirely fictional and is provided only to illustrate common medical-legal themes. It does not depict any real patient or case.

A 5-month-old infant with a large ventricular septal defect, followed by pediatric cardiology and being managed medically while awaiting surgical repair, is brought to a community emergency department with three days of poor feeding, rapid breathing, and sweating during feeds. The parents report the baby seems "more tired." Vital signs show mild tachypnea and tachycardia; oxygen saturation is normal. The infant is well-appearing on examination.

The treating physician orders a chest radiograph (read as mild cardiomegaly, unchanged from prior) and a basic metabolic panel. No natriuretic peptide is drawn. The infant is diagnosed with a viral respiratory illness and discharged with reassurance. Three days later, the infant returns in decompensated heart failure requiring intensive care.

In subsequent litigation, the plaintiff alleges that an NT-proBNP would have been markedly elevated and would have prompted admission. The defense counters that the diagnosis of worsening heart failure is clinical, that no validated outpatient NT-proBNP threshold exists to mandate admission in this setting, and that the known baseline cardiac disease — not any failure of testing — drove the deterioration. This single hypothetical captures nearly every biomarker dispute discussed below.

What These Biomarkers Actually Measure

Natriuretic peptides (BNP and NT-proBNP). When the heart's pumping chambers (ventricles) are stretched by pressure or volume overload, they release BNP; NT-proBNP is an inactive fragment produced in the same process. Both rise when the ventricle is working against an abnormal load or beginning to fail. In children with CHD, levels have been shown to correlate with ventricular volumes, ventricular function, the pressure and volume load on the ventricle, and worsening heart failure class. They are, in essence, a blood-based signal of cardiac strain. BNP and NT-proBNP convey similar information; most laboratories offer one or the other.

Cardiac troponin. Troponin is a protein released into the blood when heart muscle cells are injured or die. In adults it is the cornerstone of diagnosing myocardial infarction. In children, heart attacks are vanishingly rare, so troponin is used instead to detect myocardial injury from other causes — most commonly suspected myocarditis (heart-muscle inflammation) or chest trauma, and less often heart failure or strain. In children with CHD, troponin can rise from volume or pressure overload, from reduced oxygen delivery to the heart muscle, and markedly after cardiac surgery.

The Central Problem: No Firm Pediatric Thresholds

The single most important concept for an attorney to grasp — and the one that governs almost every expert dispute — is that the adult decision thresholds do not transfer to children.

Natriuretic peptide levels are strongly age-dependent. They are highest in newborns and infants and fall with age, and they are further influenced by sex, kidney function, obesity, and pulmonary hypertension. A value that would be alarming in a 10-year-old may be entirely normal in a neonate. The 2024 American Heart Association (AHA) scientific statement on chronic heart failure in CHD acknowledges that while natriuretic peptides correlate with disease severity, the supporting pediatric data are limited.

Troponin also varies by age. Healthy newborns and infants have relatively high troponin concentrations, which fall to a nadir around 1–3 years of age and then rise again through puberty toward adult levels. There is no formal guideline establishing troponin thresholds for diagnosing myocardial injury in children, and most reported pediatric values are extrapolated from adult 99th-percentile reference limits or derived from small studies.

Pediatric cut-offs remain largely unvalidated. Across the literature, authors repeatedly emphasize that reliable, consensus upper reference limits for these biomarkers in children — particularly in children with CHD — are not established, and that most current practice rests on expert opinion and small, often retrospective studies. One consequence is that different hospitals and laboratories may use different assays and different reference values, so results are not always directly comparable between institutions.

For litigation, this means a biomarker result is rarely a "bright line." An expert who testifies that a specific number mandated a specific action, or conclusively excluded disease, is making a claim the underlying evidence often cannot support.

What the Evidence Does Support

Despite the absence of firm cut-offs, these biomarkers carry real, evidence-based value — which is precisely why their misuse (or non-use) becomes litigable.

Natriuretic peptides track heart failure severity and prognosis. In children with CHD and heart failure, NT-proBNP rises progressively with worsening clinical severity, and markedly elevated levels have been associated with death. A JACC systematic review found BNP elevated in complex CHD even in asymptomatic patients, though with a wide range of values that limits interpretation for any individual child. A 2025 systematic review concluded that (NT-pro)BNP has demonstrated clinical value for predicting mortality and composite adverse outcomes in both adult and pediatric CHD — the biomarker with the strongest evidence base.

In single-ventricle physiology, where clinical heart-failure diagnosis is especially difficult, BNP and NT-proBNP have been shown to help detect heart failure, including across different stages of surgical palliation.

Around cardiac surgery, both NT-proBNP and high-sensitivity troponin T measured postoperatively predict adverse in-hospital outcomes, correlating with cardiopulmonary bypass time, ventilation duration, and intensive care stay; preoperative levels also carry prognostic value, and combining the two markers improves risk stratification.

Age-adjusted interpretation improves utility. Research using age-adjusted NT-proBNP has shown strong prediction of major adverse cardiovascular events across the full pediatric age range, suggesting that the age-dependence problem can be partially overcome with proper adjustment rather than raw adult thresholds.

Litigation Targets (Plaintiff-Side Themes)

The following are the categories in which biomarker use — or non-use — most often becomes a focus of litigation. Each is only as strong as the specific facts and, critically, the causation evidence.

1. Failure to obtain a biomarker when clinically indicated. The most common theme is that a natriuretic peptide (or, in a suspected-myocarditis presentation, a troponin) should have been drawn and was not. This theory is strongest where the biomarker is an established part of the relevant evaluation — for example, in distinguishing cardiac from pulmonary causes of respiratory distress in an infant with known CHD, or in evaluating suspected myocarditis in a child with viral illness and disproportionate cardiac signs. It is weakest where the diagnosis is fundamentally clinical and the test would have been confirmatory at best.

2. Misinterpreting a "normal" value as excluding disease. A defense built on a single normal biomarker can itself become a plaintiff target when the value was misapplied — for example, treating a "normal-for-adults" troponin as reassuring in an infant whose age-specific range is different, or over-reading a modestly elevated natriuretic peptide as benign in a child whose baseline is unknown. Because wide value ranges and overlapping normal/abnormal zones are well documented, point estimates can mislead.

3. Failure to act on a clearly abnormal result. Distinct from failure to test is failure to respond. A markedly elevated NT-proBNP in a symptomatic child, or a rising postoperative troponin, that is documented but not escalated can support an allegation of failure to recognize deterioration — particularly given evidence linking high levels to death and adverse outcomes.

4. Failure to trend serial values. Because single values are difficult to interpret, the direction of change over time is often more informative. Allegations may focus on a failure to repeat a biomarker in a deteriorating child, where a rising trend would have signaled worsening strain or ongoing injury.

5. Postoperative monitoring gaps. In the surgical setting, where biomarkers have the clearest prognostic validation, alleged failures to measure or respond to elevated postoperative NT-proBNP or troponin can intersect with intensive-care management claims.

Defense Themes

Several defense positions are well grounded in the same body of evidence, and attorneys evaluating either side should weigh them carefully.

1. The diagnosis is clinical; biomarkers are adjuncts. No major guideline establishes a biomarker value that, standing alone, mandates a specific disposition in a child with CHD. The AHA statement frames natriuretic peptides as helpful for guiding therapy response and prognosis — not as standalone diagnostic gatekeepers — and notes the limited pediatric data. A defensible clinical judgment supported by examination, vital-sign trends, and imaging is not negated by the absence of a blood test.

2. No validated threshold existed to breach. Where plaintiffs assert that a particular number mandated admission or intervention, the defense can point to the documented absence of consensus pediatric cut-offs and the heterogeneity of assays and reference ranges across institutions. One cannot breach a bright line that the literature has not drawn.

3. Age- and physiology-dependent confounding. Elevated levels in a child with CHD may reflect the underlying anatomy, prematurity, kidney function, pulmonary hypertension, or normal infant physiology rather than a new, actionable process — making a single elevated value non-specific.

4. Causation is usually the decisive battleground. As with most CHD litigation, the defense is often strongest on causation rather than breach. Even if a biomarker had been drawn and was abnormal, the plaintiff must still prove that earlier knowledge would, more likely than not, have changed the outcome — a difficult showing when the deterioration is driven by the natural history of the underlying heart defect.

5. A normal value can be legitimately reassuring in context. When used appropriately — with the correct age-specific reference frame and alongside clinical findings — a normal or low natriuretic peptide carries real negative predictive value, with low levels identifying children at minimal short-term risk. The defense weakness is misapplication, not use.

Common Misconceptions

"A normal troponin rules out serious heart disease in a child." False. Troponin detects myocyte injury, not all cardiac pathology; a child can have significant structural disease, heart failure, or arrhythmia with a normal troponin. Age-specific interpretation is also essential.

"An elevated BNP or NT-proBNP proves negligent heart failure management." False. Levels rise from the underlying anatomy and multiple non-cardiac factors, vary widely between individuals, and lack validated pediatric cut-offs.

"Adult cut-off values apply to children." False. Both natriuretic peptides and troponin have age-dependent normal ranges that differ substantially from adult thresholds, and using adult numbers is a recognized interpretive error.

"If the test had been drawn, the outcome would have changed." Not necessarily. This conflates a diagnostic signal with a modifiable outcome; causation must be proven separately, against the backdrop of the child's natural disease course.

Medical Records That Matter

Meaningful review of a biomarker-related CHD case typically depends on:

• The specific assay and laboratory reference range used (results are not comparable across assays)
• Age-specific context and any available baseline values for that child
• Serial/trended results rather than isolated single values
• Pediatric cardiology notes establishing the baseline anatomy, physiology, and prior biomarker levels
• Vital-sign trends and serial examinations documenting clinical trajectory
• Timing of each draw relative to symptom onset, presentation, and any surgery
• Operative and intensive-care records for postoperative biomarker interpretation
• Documentation of clinical reasoning showing how (or whether) results were integrated into decisions

Isolated lab values, divorced from assay, age, baseline, and clinical context, rarely tell the real story.

The Role of Pediatric Cardiology Expertise

Interpreting these biomarkers requires expertise that general cardiology or adult emergency medicine often cannot supply. A pediatric cardiology expert can explain how a given value should be read against a child's age and specific anatomy, whether a result was genuinely actionable given the absence of validated thresholds, whether a trend rather than a point value was the relevant signal, and — most importantly — whether earlier knowledge of a biomarker would plausibly have altered the clinical course. Because so much of this field rests on expert opinion rather than firm guideline cut-offs, the quality and objectivity of expert analysis is frequently decisive.

Key Takeaways for Attorneys

1. BNP, NT-proBNP, and troponin are useful adjuncts, not definitive tests, in children with CHD.
2. Adult cut-off values do not apply to children; normal ranges are strongly age-dependent.
3. Validated pediatric thresholds largely do not exist, so claims that a specific number mandated a specific action are often unsupportable.
4. Natriuretic peptides have the strongest evidence base, correlating with heart-failure severity and predicting adverse outcomes and mortality.
5. Troponin in children is mainly for suspected myocarditis or trauma, not heart attack, and is non-specific in CHD.
6. Trends over time are often more informative than single values.
7. Biomarkers carry the clearest prognostic validation in the surgical/postoperative setting.
8. A normal value does not exclude serious cardiac disease, and an elevated value does not by itself prove negligence.
9. Causation is usually the decisive issue — the plaintiff must show earlier knowledge would more likely than not have changed the outcome.
10. Assay, age, baseline, and clinical context are essential to any credible interpretation; isolated numbers mislead.

References

1. Aakre, Kristin M., et al. "Current and Future Indication for Testing and Use of Cardiac Troponin in Children." Clinical Chemistry, 2026.
2. Amdani, Shahnawaz, et al. "Evaluation and Management of Chronic Heart Failure in Children and Adolescents With Congenital Heart Disease: A Scientific Statement From the American Heart Association." Circulation, 2024.
3. Bohn, Mary Kathryn, et al. "Cardiac Biomarkers in Pediatrics: An Undervalued Resource." Clinical Chemistry, 2021.
4. Chowdhury, Rajarshi R., Sumeet Kaur, and Rani Gera. "N-Terminal Pro-B-Type Natriuretic Peptide as a Marker of Severity of Heart Failure in Children With Congenital Heart Diseases." Pediatric Cardiology, 2023.
5. Eindhoven, Jannet A., et al. "The Usefulness of Brain Natriuretic Peptide in Complex Congenital Heart Disease: A Systematic Review." Journal of the American College of Cardiology, 2012.
6. Ferraro, Simona, et al. "High-Sensitivity Cardiac Troponin and the Management of Congenital Heart Disease in Newborns and Infants." Clinical Chemistry, 2024.
7. Lowenthal, Alexander, et al. "Usefulness of B-Type Natriuretic Peptide and N-Terminal Pro-B-Type Natriuretic Peptide as Biomarkers for Heart Failure in Young Children With Single Ventricle Congenital Heart Disease." American Journal of Cardiology, 2012.
8. McEvoy, John W., et al. "Myocardial Injury Thresholds for Four High-Sensitivity Troponin Assays in a Population-Based Sample of US Children and Adolescents." Circulation, 2023.
9. Mori, Yoshiki, et al. "Risk Factors for Cardiac Adverse Events in Infants and Children With Complex Heart Disease Scheduled for Bi-ventricular Repair: Prognostic Value of Pre-operative B-Type Natriuretic Peptide and High-Sensitivity Troponin T." Pediatric Cardiology, 2020.
10. Palm, Jonas, et al. "Predicting Major Adverse Cardiovascular Events in Children With Age-Adjusted NT-proBNP." Journal of the American College of Cardiology, 2021.
11. Shen, Hua, et al. "Predictive Value of NT-proBNP and Hs-TnT for Outcomes After Pediatric Congenital Cardiac Surgery." International Journal of Surgery, 2024.
12. van Genuchten, Wouter J., et al. "Clinical Impact of Circulating Biomarkers in Prediction of Adverse Cardiac Events in Patients With Congenital Heart Disease: A Systematic Review." International Journal of Cardiology, 2025.