Blood proteins reveal right ventricular remodeling after tetralogy of Fallot repair

Adolescents with repaired tetralogy of Fallot who have moderate to severe dilation of the right ventricle carry a measurably different fingerprint of proteins in their blood compared with peers whose right ventricles are less enlarged, according to a new proof-of-concept study published in Pediatric Research. The team, led by investigators at the Children's Hospital of Philadelphia, combined untargeted serum proteomics with cardiac magnetic resonance imaging (CMR) to characterize right ventricular remodeling in youth after surgical repair of the congenital heart defect. The researchers report that the altered proteins point toward a shift in the heart's fuel sources and toward oxidative stress responses, offering some of the first circulating molecular clues about how the right ventricle adapts, and potentially begins to fail, after childhood repair.

Although long-term survival after surgical repair of tetralogy of Fallot is now excellent, most patients are left with residual lesions. These residuals, typically pulmonary insufficiency or residual pulmonary stenosis, impose chronic hemodynamic stress on the right ventricle. The chamber initially responds with an adaptive state of dilation and compensatory hypertrophy, but over time this can transition to a maladaptive state marked by dysfunction, failure, and increased risk of death.

In adulthood, the prevalence of right ventricular failure after tetralogy of Fallot repair increases by approximately 10 percent every 10 years. Patients are routinely followed with echocardiography and CMR, which is considered the gold standard for measuring right ventricular volumes, hypertrophy, and function, quantifying residual pulmonary regurgitation and stenosis, and assessing myocardial fibrosis. What has been missing is a complementary molecular window into the remodeling process itself.

Circulating proteins associated with adverse ventricular remodeling have been described in adult conditions such as atrial fibrillation, hypertensive heart failure, and dilated cardiomyopathy, but their role in tetralogy of Fallot has been understudied. Earlier work by the same group and others had shown that children and adolescents with repaired tetralogy of Fallot display altered regulation of metabolic and extracellular matrix remodeling proteins. The new study set out to demonstrate the feasibility of measuring the serum proteome in this population and to identify candidate markers of right ventricular remodeling, specifically dilation measured on CMR.

The stakes are high because right ventricular failure is notoriously difficult to treat and does not respond to standard therapies developed for left ventricular failure. There is also an unresolved clinical question about the optimal timing of pulmonary valve replacement. The study was a cross-sectional observational investigation of patients with repaired tetralogy of Fallot presenting for a clinically indicated CMR at the Children's Hospital of Philadelphia between February 2021 and July 2021.

Participants had undergone complete surgical repair, defined as ventricular septal defect closure with or without right ventricular outflow tract intervention such as a valve-sparing procedure, transannular patch, or a conduit from the right ventricle to the pulmonary artery. Patients who had already undergone pulmonary valve replacement were excluded. Blood samples were collected at the time of intravenous placement for the CMR, and serum was processed for proteomic analysis.

CMR studies were performed on room air without sedation on a 1.5 Tesla scanner, using balanced steady-state free-precession cine acquisitions with contiguous short-axis imaging from the base of the heart to the apex. Fourteen adolescents were enrolled, with a median age of 16 years and an interquartile range of 15 to 18 years. Most had originally presented with tetralogy of Fallot with pulmonary stenosis, and 13 of the 14 had been repaired with a transannular patch.

The investigators divided the cohort into two phenogroups based on the median indexed right ventricular end-diastolic volume. Group 1 comprised nine patients with a median indexed end-diastolic volume of 146 milliliters per square meter, while Group 2 comprised five patients with a median of 114 milliliters per square meter, a statistically significant difference. Indexing the volume to body surface area raised to the power of 1.3, an alternative normalization scheme, produced the same grouping, indicating the result was robust to the indexing method used.

Several clinical and imaging differences emerged between the groups. Patients in Group 1 were younger at the time of CMR, with a median age of 15 years compared with 18 years in Group 2, which the authors suggest may indicate two distinct populations of right ventricular remodeling rather than a single trajectory of disease progression. Group 1 also exhibited a shorter native T1 relaxation time, 993 milliseconds versus 1023 milliseconds, though both values were within normal limits and there was no significant difference in extracellular volume, suggesting no clinically meaningful difference in diffuse fibrosis between the groups.

Group 1 had a higher indexed right ventricular stroke volume, 85 versus 59 milliliters per square meter, with a similar ejection fraction. The right ventricular mass-to-volume ratio was lower in Group 1, though not statistically significantly, a pattern the authors note could be consistent with maladaptive remodeling. There were no significant differences in pulmonary regurgitant fraction, ventricular efficiency, or outflow tract obstruction.

On the proteomics side, the team used data-independent acquisition mass spectrometry on a Q Exactive HF instrument coupled to a nano-scale liquid chromatography system, processing the raw data with Spectronaut software in direct DIA mode against a curated human protein database. More than 400 proteins were quantified in each individual's serum, and after filtering out proteins detected in fewer than half of the patients, 546 proteins remained for statistical comparison. Two proteins, the proteasome subunits PSMA4 and PSMA5, were detected only in Group 1, the more dilated group, and no proteins were unique to Group 2.

In total, the researchers identified 60 differentially abundant proteins at a p value below 0.05 and a log2 fold change of at least 1.2, of which 55 were increased and 5 were decreased in the more dilated group. Because this was a small feasibility study, no correction for multiple comparisons was applied. Pathway enrichment analysis revealed the biological themes behind these differences.

Gene Ontology analysis flagged catabolism, nucleotide metabolism, and detoxification as the top enriched biological processes, with nearly half of the differentially abundant proteins tied to catabolism. Reactome pathway analysis highlighted increases in proteins involved in neutrophil degranulation, the KEAP-NFE2L2 oxidative stress response pathway, interleukin-12 signaling, and the regulation of glucose and carbohydrate metabolism. The pattern points to metabolic reprogramming: proteins involved in glycolysis, including GAPDH, HAGH, FUCA1, and BPGM, were upregulated in the more dilated ventricles, while LGMN, a protein involved in lipid metabolism regulation, was among the few that decreased.

This shift from fatty acid oxidation toward carbohydrate use mirrors findings in animal models of both pressure-loaded and volume-loaded right ventricles, and while glycolysis requires less oxygen, it yields less ATP and promotes inflammation, potentially creating a chronically energy-depleted state. The protein changes also suggested a mixture of adaptive and maladaptive signaling. On the adaptive side, the more dilated group showed increased abundance of proteins that neutralize reactive oxygen species, including members of the peroxiredoxin family, thioredoxin, catalase, and superoxide dismutase, along with proteins involved in protein quality control, calcium signaling such as CALM1 and RYR2, and smooth muscle regulation such as ACTA2.

The authors interpret these as possible attempts to combat oxidative damage to proteins, calcium handling, and vascular tone. On the maladaptive side, the group showed elevations of tenascin C, an extracellular matrix protein associated with cardiac remodeling, inflammation, and fibrosis; hemoglobin subunit beta, a product of heme oxidation linked to inflammation and fibrosis; and EIF5A, a regulator of protein synthesis increased in models of cardiac fibrosis. Meanwhile, telomerase reverse transcriptase, or TERT, which maintains telomeres and chromosomal stability, was downregulated, and loss of TERT has been linked to impaired cardiac recovery and increased risk of arrhythmia and heart failure.

Exploratory analyses, though based on very few patients, added intriguing leads. Seven participants underwent cardiopulmonary exercise testing a median of 1.1 years after their CMR; three were classified as high performers and four as low performers based on percent-predicted maximum oxygen consumption. Compared with high performers, the low performers showed decreased abundance of proteins in pathways involving integrin signaling, peptide metabolism, and extracellular matrix organization, and increased abundance of titin, a sarcomeric structural protein whose circulating fragments have been reported in myocarditis, myocardial infarction, and dilated cardiomyopathy, which the authors suggest may reflect cardiomyocyte structural injury.

Four patients had follow-up CMR about two years later; in the two whose right ventricular mass-to-volume ratio decreased, potentially indicating maladaptive remodeling, proteins involved in the adaptive immune response were more abundant. The authors emphasize that the study's small sample of fourteen patients, the lack of multiple-comparison correction, the age difference between groups, and the inability to confirm that circulating proteins originate from the heart all limit interpretation. Still, they conclude that serum proteomics is feasible in this population and that confirmatory research could eventually integrate protein profiling into prognostication and clinical decision making after tetralogy of Fallot repair.

Subject of Research: Serum proteomic signatures of right ventricular dilation in adolescents after tetralogy of Fallot repair

Article Title: A complementary proteomics and cardiac magnetic resonance approach to characterize right ventricular remodeling after tetralogy of Fallot repair

Article References: Jones, A. L., Edwards, J. J., Fazelinia, H., Frank, D., Clouthier, K. L., Patel, C., Spruce, L., Ding, H., Sabella, J., Avitabile, C. M., Friedberg, M. K., Fogel, M. A., Ischiropoulos, H., Reddy, S., & Mercer-Rosa, L. (2026). A complementary proteomics and cardiac magnetic resonance approach to characterize right ventricular remodeling after tetralogy of Fallot repair. Pediatric Research. https://doi.org/10.1038/s41390-026-05555-7

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05555-7

Keywords: tetralogy of Fallot, right ventricular remodeling, proteomics, cardiac magnetic resonance, congenital heart disease, pulmonary insufficiency, metabolic reprogramming, oxidative stress, glycolysis, fibrosis, pediatric cardiology, biomarkers