Altered Cholesterol Metabolism and Hypocholesterolemia in Patients with Single Ventricle following Fontan Palliation

Insulin Resistance after Fontan Palliation

Patients with a single ventricle heart who had Fontan palliation (S/P Fontan) are at increased risk for acquired morbidity. Insulin resistance (IR) is a predictor of cardiac morbidity and mortality. A single-center, cross-sectional study using S/P Fontan and controls was designed to assess IR S/P Fontan. Group comparisons were made in IR via the Quantitative Insulin Index (QUICKI) and the natural log-transformed homeostasis model assessment, ln (HOMA-IR), without/with adjusting for age. A total of 89 patients (59 Fontan and 30 controls) were included. Fontan patients showed a significant decrease in QUICKI (0.34 ± 0.03 vs 0.37 ± 0.02) and an elevation of ln (HOMA-IR) (0.82 ± 0.62 vs 0.24 ± 0.44) compared to controls (both p < 0.0001); this remained significant even adjusting for age. With older age, there was a significant, progressive decrease in QUICKI (p = 0.01) and an increase in ln (HOMA-IR) (p = 0.02) S/P Fontan. Analysis excluding Fontan patients with obesity still showed a significant reduction of QUICKI and an elevation of ln (HOMA-IR) in Fontan patients compared to controls when adjusting for age (both p < 0.05). Using QUICKI, IR was present in 41 (69.5%) Fontan patients vs. 3 (10%) controls (p < 0.0001) and using HOMA-IR, IR was present in 32 (54.2%) vs 5 (16.7%) controls (p = 0.001). Fontan patients had significantly more IR compared to controls and the prevalence of IR increases with age. Since IR is known to correlate with long-term morbidity and mortality and can be ameliorated by therapies, we believe it is critical that IR be identified as early as possible in Fontan patients.

Examination of Postoperative Changes in Lipid Profile and Glycemic Markers After Coronary Artery Bypass Graft, Percutaneous Intervention Vs Aortic Valve Replacement Demonstrated a Shift in Risk Factors for Coronary Artery Disease

Purpose

Surgery-related stress may affect the metabolome, leading to abnormal lipid profiles and ineffective glycemic control. Here, we gauge these changes as they may accelerate atherosclerosis, limiting the benefits of interventions aimed at improving coronary artery disease (CAD) progression.

Patients and Methods

Electronic medical records were queried to identify patients undergoing coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI), or aortic valve replacement (AVR). 7573 records denoted lipid profile (cholesterol, LDL, HDL, VLDL, triglycerides) and glucose metabolism impairment (HbA1c). Pre-procedure lipid and glucose laboratory values were compared with periods representing acute periprocedural inflammation (1-3 months), resolution of acute inflammation (3-6 months), convalescence (6-12 months), and medium- (1-2 years), and long-term periods (2-5 years).

Results

Baseline values differed between groups (AVR: Cholesterol↑↓, LDL↓↑, HDL↓, Triglycerides↑, HbA1c↓; CABG: Cholesterol↓, LDL↓, HDL↓, Triglycerides↓, HbA1c↓; PCI: Cholesterol↑↓, LDL↑↓, HDL↑↓, Triglycerides↓, HbA1c↓). Interestingly, total cholesterol and LDL had opposite trajectories after CABG vs AVR even five years after surgical procedure and the effects were moderate as denoted by d-Cohen statistics. HDL declined acutely after CABG and AVR but not after PCI. Triglycerides were elevated for 2 years after AVR but depressed after CABG and PCI. HbA1c remained depressed for up to 5 years after any studied procedure.

Conclusion

Our data suggest surgical procedures result in prolonged lipid profile and glycemic metabolism disturbances, particularly after aortic valve replacement, indicating more aggressive post-surgical treatment of these metabolic abnormalities may be warranted.

Liver fibrosis detected by diffusion-weighted magnetic resonance imaging and its functional correlates in Fontan patients

OBJECTIVES

The evaluation of Fontan-associated liver disease is often challenging. Diffusion-weighted magnetic resonance imaging can detect hepatic fibrosis from capillary perfusion and diffusion abnormalities from extracellular matrix accumulation. This study investigated its role in the evaluation of liver disease in Fontan patients and explored possible diagnostic methods for early detection of advanced liver fibrosis.

METHODS

Stable adult Fontan patients who could safely be examined with magnetic resonance imaging were enrolled, and blood biomarkers, transient elastography were also examined.

RESULTS

Forty-six patients received diffusion-weighted imaging; and 58.7% were diagnosed with advanced liver fibrosis (severe liver fibrosis, 37.0%, and cirrhosis 21.7%). Two parameters of hepatic dysfunction, platelet counts (Spearman's ρ: -0.456, P = 0.001) and cholesterol levels (Spearman's ρ: -0.383, P = 0.009), decreased with increasing severity of fibrosis. Using transient elastography, a cut-off value of 14.2 kPa predicted the presence of advanced liver fibrosis, but with a low positive predictive value. When we included platelet count, cholesterol, post-Fontan years and transient elastography values as a composite, the capability of predicting advanced liver fibrosis was the most satisfactory (C statistic 0.817 ± 0.071, P < 0.001). A cut-off value of 5.0 revealed a sensitivity of 78% and a specificity of 82%.

CONCLUSIONS

In Fontan patients, diffusion-weighted imaging was helpful in detecting liver fibrosis that was correlated with hepatic dysfunction. A simple score was proposed for long-term surveillance and early detection of advanced liver disease in adult Fontan patients. For adult Fontan patients with a calculated score > 5.0, we may consider timely diffusion-weight imaging and early management for liver complications.

Altered Serum Proteins Suggest Inflammation, Fibrogenesis and Angiogenesis in Adult Patients with a Fontan Circulation

Previous omics research in patients with complex congenital heart disease and single-ventricle circulation (irrespective of the stage of palliative repair) revealed alterations in cardiac and systemic metabolism, inter alia abnormalities in energy metabolism, and inflammation, oxidative stress or endothelial dysfunction. We employed an affinity-proteomics approach focused on cell surface markers, cytokines, and chemokines in the serum of 20 adult Fontan patients with a good functioning systemic left ventricle, and we 20 matched controls to reveal any specific processes on a cellular level. Analysis of 349 proteins revealed 4 altered protein levels related to chronic inflammation, with elevated levels of syndecan-1 and glycophorin-A, as well as decreased levels of leukemia inhibitory factor and nerve growth factor-ß in Fontan patients compared to controls. All in all, this means that Fontan circulation carries specific physiological and metabolic instabilities, including chronic inflammation, oxidative stress imbalance, and consequently, possible damage to cell structure and alterations in translational pathways. A combination of proteomics-based biomarkers and the traditional biomarkers (uric acid, γGT, and cholesterol) performed best in classification (patient vs. control). A metabolism- and signaling-based approach may be helpful for a better understanding of Fontan (patho-)physiology. Syndecan-1, glycophorin-A, leukemia inhibitory factor, and nerve growth factor-ß, especially in combination with uric acid, γGT, and cholesterol, might be interesting candidate parameters to complement traditional diagnostic imaging tools and the determination of traditional biomarkers, yielding a better understanding of the development of comorbidities in Fontan patients, and they may play a future role in the identification of targets to mitigate inflammation and comorbidities in Fontan patients.

Nutritional considerations for people living with a Fontan circulation: a narrative review

The population of people living with a Fontan circulation are highly heterogenous, including both children and adults, who have complex health issues and comorbidities associated with their unique physiology throughout life. Research focused on nutritional considerations and interventions in the Fontan population is extremely limited beyond childhood. This review article discusses the current literature examining nutritional considerations in the setting of Fontan physiology and provides an overview of the available evidence to support nutritional management strategies and future research directions. Protein-losing enteropathy, growth deficits, bone mineral loss, and malabsorption are well-recognised nutritional concerns within this population, but increased adiposity, altered glucose metabolism, and skeletal muscle deficiency are also more recently identified issues. Emergencing evidence suggets that abnormal body composition is associated with poor circulatory function and health outcomes. Many nutrition-related issues, including the impact of congenital heart disease on nutritional status, factors contributing to altered body composition and comorbidities, as well as the role of the microbiome and metabolomics, remain poodly understood.

Dyslipidemia in adults with congenital heart disease: A systematic review and meta-analysis

AIMS

Several particular characteristics of patients with congenital heart disease could affect lipid levels. The objectives of this study were: a) to analyze the prevalence of dyslipidemia in congenital heart disease patients; 2) to compare lipid levels between congenital heart disease patients and a control group.

DATA SYNTHESIS

This systematic review and meta-analysis was performed according to PRISMA guidelines (PROSPERO CRD42023432041). A literature search was performed to detect studies that have reported lipid levels or the prevalence of dyslipidemia in congenital heart disease patients. We performed a qualitative analysis (studies that reported dyslipidemia prevalence) and quantitative analysis (studies that compared lipid values between congenital heart disease patients and controls). In total, 29 observational studies involving 22,914 patients with congenital heart disease and 641,086 controls were eligible for this review. The reported presence of "hyperlipidemia" or "dyslipidemia" ranged from 14.3% to 69.9%. When studies analyzed lipid variables dichotomously between congenital heart disease patients and controls, the results were conflicting. The quantitative analysis showed that patients with congenital heart disease have lower levels of total cholesterol (MD: -18.9 [95% CI: -22.2 to -15.7]; I2 = 93%), LDL-C (MD: -10.7 [95% CI: -13.1 to -8.3]; I2 = 90%) and HDL-C (MD: -6.3 [95% CI: -7.7 to -4.9]; I2 = 95%) compared to controls.

CONCLUSIONS

The qualitative analysis showed some concerns, but the quantitative analysis indicates that congenital heart disease patients showed lower levels of total cholesterol, LDL-C, and HDL-C compared to controls. New research should be developed to clarify this relevant topic.

The proteomic fingerprint in infants with single ventricle heart disease in the interstage period: evidence of chronic inflammation and widespread activation of biological networks

Introduction

Children with single ventricle heart disease (SVHD) experience significant morbidity across systems and time, with 70% of patients experiencing acute kidney injury, 33% neurodevelopmental impairment, 14% growth failure, and 5.5% of patients suffering necrotizing enterocolitis. Proteomics is a method to identify new biomarkers and mechanisms of injury in complex physiologic states.

Methods

Infants with SVHD in the interstage period were compared to similar-age healthy controls. Serum samples were collected, stored at -80°C, and run on a panel of 1,500 proteins in single batch analysis (Somalogic Inc., CO). Partial Least Squares-Discriminant Analysis (PLS-DA) was used to compare the proteomic profile of cases and controls and t-tests to detect differences in individual proteins (FDR <0.05). Protein network analysis with functional enrichment was performed in STRING and Cytoscape.

Results

PLS-DA readily discriminated between SVHD cases (n = 33) and controls (n = 24) based on their proteomic pattern alone (Accuracy = 0.96, R2 = 0.97, Q2 = 0.80). 568 proteins differed between groups (FDR <0.05). We identified 25 up-regulated functional clusters and 13 down-regulated. Active biological systems fell into six key groups: angiogenesis and cell proliferation/turnover, immune system activation and inflammation, altered metabolism, neural development, gastrointestinal system, and cardiac physiology and development.

Conclusions

We report a clear differentiation in the circulating proteome of patients with SVHD and healthy controls with >500 circulating proteins distinguishing the groups. These proteomic data identify widespread protein dysregulation across multiple biologic systems with promising biological plausibility as drivers of SVHD morbidity.

Comparative Metabolomics in Single Ventricle Patients after Fontan Palliation: A Strong Case for a Targeted Metabolic Therapy

Most studies on single ventricle (SV) circulation take a physiological or anatomical approach. Although there is a tight coupling between cardiac contractility and metabolism, the metabolic perspective on this patient population is very recent. Early findings point to major metabolic disturbances, with both impaired glucose and fatty acid oxidation in the cardiomyocytes. Additionally, Fontan patients have systemic metabolic derangements such as abnormal glucose metabolism and hypocholesterolemia. Our literature review compares the metabolism of patients with a SV circulation after Fontan palliation with that of patients with a healthy biventricular (BV) heart, or different subtypes of a failing BV heart, by Pubmed review of the literature on cardiac metabolism, Fontan failure, heart failure (HF), ketosis, metabolism published in English from 1939 to 2023. Early evidence demonstrates that SV circulation is not only a hemodynamic burden requiring staged palliation, but also a metabolic issue with alterations similar to what is known for HF in a BV circulation. Alterations of fatty acid and glucose oxidation were found, resulting in metabolic instability and impaired energy production. As reported for patients with BV HF, stimulating ketone oxidation may be an effective treatment strategy for HF in these patients. Few but promising clinical trials have been conducted thus far to evaluate therapeutic ketosis with HF using a variety of instruments, including ketogenic diet, ketone esters, and sodium-glucose co-transporter-2 (SGLT2) inhibitors. An initial trial on a small cohort demonstrated favorable outcomes for Fontan patients treated with SGLT2 inhibitors. Therapeutic ketosis is worth considering in the treatment of Fontan patients, as ketones positively affect not only the myocardial energy metabolism, but also the global Fontan physiopathology. Induced ketosis seems promising as a concerted therapeutic strategy.

Dyslipidemia Among Adults With Congenital Heart Disease

Background

Atherosclerotic disease is an important cause of morbidity among adults with congenital heart disease (CHD). Prevalence of dyslipidemia in this group is poorly described.

Objectives

This study aimed to describe the prevalence of dyslipidemia among adults with CHD.

Methods

A prospective, outpatient screening study was conducted among adults aged ≥18 years at 4 New England ambulatory congenital cardiology centers. Participants were surveyed regarding cardiovascular risk factors. Nonfasting fingerstick samples were obtained for analysis using a point-of-care lipid analyzer.

Results

Lipid screening was completed on 186 participants (median age 30 [range 18-71] years, 50% female). Eighteen (10%) had simple CHD anatomy, and 63 (34%) had complex anatomy. Only 15% of 169 respondents reported history of high cholesterol. Eighty-five (46%) participants met National Cholesterol Education Program definition of dyslipidemia with 60 (32%), 62 (34%), and 37 (20%) having low high-density lipoprotein cholesterol (HDL-C <40 mg/dL), high non-HDL-C (≥130 mg/dL), and high total cholesterol (TC ≥200 mg/dL), respectively. TC was higher among participants with simple CHD than among those with moderate and complex lesions (mean 178.4 ± 48.7 vs 170.1 ± 35.0 vs 157.6 ± 34.5 mg/dL; P = 0.03). HDL-C was lower among participants with complex CHD than among those with simple and moderate lesions (mean 44.1 ± 13.5 vs 46.9 ± 12.5 vs 49.8 ± 15.3 mg/dL; P = 0.05).

Conclusions

Dyslipidemia is highly prevalent among our cohort of adults with CHD, despite <15% reporting a prior diagnosis. Low HDL-C was more common in complex CHD, and high TC was more common in simple or moderate CHD. Lipid screening should be part of preventive health maintenance for all adults with CHD.

Fontan Circulation Associated Organ Abnormalities Beyond the Heart, Lungs, Liver, and Gut: A Systematic Review

Introduction

Patients with a Fontan circulation are at risk for sequelae of Fontan physiology during follow-up. Fontan physiology affects all organ systems and an overview of end-organ damage is needed.

Methods

We performed a systematic review of abnormalities in multiple organ systems for patients with a longstanding Fontan circulation. We searched online databases for articles describing abnormalities in multiple organ systems. Cardio-pulmonary abnormalities, protein losing enteropathy, and Fontan associated liver disease have already extensively been described and were excluded from this systematic review.

Results

Our search returned 5,704 unique articles. After screening, we found 111 articles relating to multiple organ systems. We found abnormalities in, among others, the nervous system, pituitary, kidneys, and musculoskeletal system. Pituitary edema—relating to the unique pituitary vasculature- may affect the thyroid axis. Renal dysfunction is common. Creatinine based renal function estimates may be inappropriate due to myopenia. Both lean muscle mass and bone mineral density are decreased. These abnormalities in multiple organ systems may be related to Fontan physiology, cyanosis, iatrogenic factors, or lifestyle.

Conclusions

Health care providers should be vigilant for hypothyroidism, visual or hearing deficits, and sleep disordered breathing in Fontan patients. We recommend including cystatin C for assessment of renal function. This review may aid health care providers and guide future research.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021232461, PROSPERO, identifier: CRD42021232461.

Identification of metabolomic profile related to adult Fontan pathophysiology

Background

Metabolic disorders are important pathophysiologies that can cause multiple organ dysfunction and worsen prognosis in Fontan patients. This study aimed to comprehensively evaluate the metabolomic profile of adult Fontan patients and characterize its pathophysiology in relation to 2 control groups.

Methods and Results

We performed metabolomic analysis of 31 plasma samples using capillary electrophoresis time-of-flight mass spectrometry. This observational cross-sectional study compared plasma metabolites of 14 heterogeneous adult Fontan patients with those of control groups, including 9 patients with congenital heart disease after biventricular repair and 8 normal healthy controls. Fontan patients exhibited significant differences in intermediate metabolite concentrations related to glycolysis, the tricarboxylic acid (TCA) cycle, and the urea cycle. The plasma concentrations of lactic acid, 2-oxoglutarate, isocitric acid, malic acid, cis-aconitic acid, arginine, citrulline, and the ratio of ornithine/citrulline showed significantly differences among the groups. Multiple logistic regression analysis with a stepwise selection-elimination method identified 2-oxoglutaric acid (odds ratio [OR] 1.98, 95% confidence interval [CI] 1.05–3.76) and cis-aconitic acid (OR 2.69, 95% CI 1.04–6.99) as independently associated with Fontan patients. After adjustment for the covariates of age and gender, 2-oxoglutaric acid (OR 1.97, 95% CI 0.98–3.93) and cis-aconitic acid (OR 3.88, 95% CI 0.99–15.2) showed remarkable relationships with Fontan patients.

Conclusions

The present findings suggest that abnormalities in the TCA cycle and amino acid metabolism are distinguishing features in the pathophysiology of Fontan patients. Future metabolomic studies will assist in developing biomarkers for the early prediction of “silent” Fontan pathophysiologies.

Long-Term Abnormalities of Lipid Profile After a Single Episode of Sepsis

Background: Acute disturbances of the lipid profile are commonplace during acute sepsis episode. However, their long-term persistence has not to be investigated despite pivotal role of dyslipidemia in several comorbidities excessively noted in sepsis survivors (stroke, cardiomyopathy). Methods: A total of 9,861 individuals hospitalized for a singular episode of sepsis between 2009 and 2019 were identified from electronic medical records. Lab measurements of total cholesterol (Tchol), high-density lipoprotein (HDL-c), low-density lipoprotein (LDL-c), very low-density lipoprotein (VLDL), triglycerides (TG), lipoprotein(a) [Lp (a)], apolipoprotein B (ApoB), and C-reactive protein (CRP). The data were examined as baseline values before sepsis, during hospitalization, and <3 months, 3-6 months, 6-12 months, 1-2 years, and more than 2 years from initial sepsis. Results: Significant reductions in HDL-c (HDLbaseline = 44.06 vs. HDLsepsis = 28.2; U = -37.79, p < 0.0001, Cohen's d = 0.22) and LDL-c serum levels were observed during and up to three months post sepsis, with females much less affected. In contrast, male subjects had derangement in HDL present for up to two years after a singular septic episode. Total cholesterol levels were slightly yet significantly elevated for up to two years after sepsis. TG were elevated up to one year [TGbaseline = 128.26 vs. TGsepsis = 170.27, t(8255) = -21.33, p < 0.0001, Cohen's d = 0.49] and normalized. Lp(a) was elevated up to two years after initial episode [Lp(a)baseline = 24.6 ± 16.06; Lp(a)sepsis-2year = 8.25 ± 5.17; Lp(a)morethan2years = 61.4 ± 40.1; ANOVA F (2, 24) = 7.39; p = 0.0032]. Response to statin therapy was blunted in sepsis survivors for several years after sepsis resolution. Significant drop-out in prescription of statins and niacin after sepsis was observed. Serum high sensitivity C-reactive protein was elevated for up to five years after sepsis resolution (H [6;1685] = 502.2; p < 0.0001). Discussion: Lipid abnormalities persisted long after the initial septic insult suggesting potential role in accelerating atherosclerosis and other abnormalities. In addition, sepsis seems to blunt statin effectiveness. Additionally, a significant and unexplained drop in statin use was seen in post-septic period. Conclusions: Our study suggests that persistent derangements of lipid profile components for up to two years after sepsis may be associated with altered risk of atherosclerosis-related events among sepsis survivors.

Metabolic profiles identify circulating biomarkers associated with heart failure in young single ventricle patients

BACKGROUND

Children and young adults with single ventricle (SV) heart disease frequently develop heart failure (HF) that is intractable and difficult to treat. Our understanding of the molecular and biochemical reasons underlying this is imperfect. Thus, there is an urgent need for biomarkers that predict outcome and provide a rational basis for treatment, and advance our understanding of the basis of HF.

OBJECTIVE

We sought to determine if a metabolomic approach would provide biochemical signatures of HF in SV children and young adults. If significant, these analytes might serve as biomarkers to predict outcome and inform on the biological mechanism(s) of HF.

METHODS

We applied a multi-platform metabolomics approach composed of mass spectrometry (MS) and nuclear magnetic resonance (NMR) which yielded 495 and 26 metabolite measurements respectively. The plasma samples came from a cross-sectional set of young SV subjects, ages 2-19 years with ten control (Con) subjects and 16 SV subjects. Of the SV subjects, nine were diagnosed as congestive HF (SVHF), and 7 were not in HF. Metabolomic data were correlated with clinical status to determine if there was a signature associated with HF.

RESULTS

There were no differences in age, height, weight or sex between the 3 cohorts. However, statistical analysis of the metabolomic profiles using ANOVA revealed 44 metabolites with significant differences between cohorts including 41 profiled by MS and 3 by NMR. These metabolites included acylcarnitines, amino acids, and bile acids, which distinguished Con from all SV subjects. Furthermore, metabolite profiles could distinguish between SV and SVHF subjects.

CONCLUSION

These are the first data to demonstrate a clear metabolomic signature associated with HF in children and young adults with SV. Larger studies are warranted to determine if these findings are predictive of progression to HF in time to provide intervention.

Fontan-Associated Dyslipidemia

Background

Hypocholesterolemia is a marker of liver disease, and patients with a Fontan circulation may have hypocholesterolemia secondary to Fontan‐associated liver disease or inflammation. We investigated circulating lipids in adults with a Fontan circulation and assessed the associations with clinical characteristics and adverse events.

Methods and Results

We enrolled 164 outpatients with a Fontan circulation, aged ≥18 years, in the Boston Adult Congenital Heart Disease Biobank and compared them with 81 healthy controls. The outcome was a combined outcome of nonelective cardiovascular hospitalization or death. Participants with a Fontan (median age, 30.3 [interquartile range, 22.8–34.3 years], 42% women) had lower total cholesterol (149.0±30.1 mg/dL versus 190.8±41.4 mg/dL, P<0.0001), low‐density lipoprotein cholesterol (82.5±25.4 mg/dL versus 102.0±34.7 mg/dL, P<0.0001), and high‐density lipoprotein cholesterol (42.8±12.2 mg/dL versus 64.1±16.9 mg/dL, P<0.0001) than controls. In those with a Fontan, high‐density lipoprotein cholesterol was inversely correlated with body mass index (r=−0.30, P<0.0001), high‐sensitivity C‐reactive protein (r=−0.27, P=0.0006), and alanine aminotransferase (r=−0.18, P=0.02) but not with other liver disease markers. Lower high‐density lipoprotein cholesterol was independently associated with greater hazard for the combined outcome adjusting for age, sex, body mass index, and functional class (hazard ratio [HR] per decrease of 10 mg/dL, 1.37; 95% CI, 1.04–1.81 [P=0.03]). This relationship was attenuated when log high‐sensitivity C‐reactive protein was added to the model (HR, 1.26; 95% CI, 0.95–1.67 [P=0.10]). Total cholesterol, low‐density lipoprotein cholesterol, and triglycerides were not associated with the combined outcome.

Conclusions

The Fontan circulation is associated with decreased cholesterol levels, and lower high‐density lipoprotein cholesterol is associated with adverse outcomes. This association may be driven by inflammation. Further studies are needed to understand the relationship between the severity of Fontan‐associated liver disease and lipid metabolism.

Method comparison of HPLC-ninhydrin-photometry and UHPLC-PITC-tandem mass spectrometry for serum amino acid analyses in patients with complex congenital heart disease and controls

INTRODUCTION

Metabolomics studies are not routine when quantifying amino acids (AA) in congenital heart disease (CHD).

OBJECTIVES

Comparative analysis of 24 AA in serum by traditional high-performance liquid chromatography (HPLC) based on ion exchange and ninhydrin derivatisation followed by photometry (PM) with ultra-high-performance liquid chromatography and phenylisothiocyanate derivatisation followed by tandem mass spectrometry (TMS); interpretation of findings in CHD patients and controls.

METHODS

PM: Sample analysis as above (total run time, ~ 119 min). TMS: Sample analysis by AbsoluteIDQ® p180 kit assay (BIOCRATES Life Sciences AG, Innsbruck, Austria), which employs PITC derivatisation; separation of analytes on a Waters Acquity UHPLC BEH18 C18 reversed-phase column, using water and acetonitrile with 0.1% formic acid as the mobile phases; and quantification on a Triple-Stage Quadrupole tandem mass spectrometer (Thermo Fisher Scientific, Waltham, MA) with electrospray ionisation in the presence of internal standards (total run time, ~ 8 min). Calculation of coefficients of variation (CV) (for precision), intra- and interday accuracies, limits of detection (LOD), limits of quantification (LOQ), and mean concentrations.

RESULTS

Both methods yielded acceptable results with regard to precision (CV < 10% PM, < 20% TMS), accuracies (< 10% PM, < 34% TMS), LOD, and LOQ. For both Fontan patients and controls AA concentrations differed significantly between methods, but patterns yielded overall were parallel.

CONCLUSION

Serum AA concentrations differ with analytical methods but both methods are suitable for AA pattern recognition. TMS is a time-saving alternative to traditional PM under physiological conditions as well as in patients with CHD.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier NCT03886935, date of registration March 27th, 2019 (retrospectively registered).

Targeted metabolomic analysis of serum amino acids in the adult Fontan patient with a dominant left ventricle

Growing interest lies in the assessment of the metabolic status of patients with a univentricular circulation after Fontan operation, especially in changes of amino acid metabolism. Using targeted metabolomic examinations, we investigated amino acid metabolism in a homogeneous adult Fontan-patient group with a dominant left ventricle, seeking biomarker patterns that might permit better understanding of Fontan pathophysiology and early detection of subtle ventricular or circulatory dysfunction. We compared serum amino acid levels (42 analytes; AbsoluteIDQ p180 kit, Biocrates Life Sciences, Innsbruck, Austria) in 20 adult Fontan patients with a dominant left ventricle and those in age- and sex-matched biventricular controls. Serum concentrations of asymmetric dimethylarginine, methionine sulfoxide, glutamic acid, and trans-4-hydroxyproline and the methionine sulfoxide/methionine ratio (Met-SO/Met) were significantly higher and serum concentrations of asparagine, histidine, taurine, and threonine were significantly lower in patients than in controls. Met-SO/Met values exhibited a significant negative correlation with oxygen uptake during exercise. The alterations in amino acid metabolome that we found in Fontan patients suggest links between Fontan pathophysiology, altered cell energy metabolism, oxidative stress, and endothelial dysfunction like those found in biventricular patients with congestive heart failure. Studies of extended amino acid metabolism may allow better understanding of Fontan pathophysiology that will permit early detection of subtle ventricular or circulatory dysfunction in Fontan patients.

Targeted metabolomic analysis of serum phospholipid and acylcarnitine in the adult Fontan patient with a dominant left ventricle

BACKGROUND

Patients with a Fontan circulation have altered cholesterol and lipoprotein values. We analysed small organic molecules in extended phopsholipid and acylcarnitine metabolic pathways ('metabolomes') in adult Fontan patients with a dominant left ventricle, seeking differences between profiles in baseline and Fontan circulations.

METHODS

In an observational matched cross-sectional study, we compared phosphatidylcholine (PC), sphingomyelin (SM), and acylcarnitine metabolomes (105 analytes; AbsoluteIDQ® p180 kit (Biocrates Life Sciences AG, Innsbruck, Austria) in 20 adult Fontan patients having a dominant left ventricle with those in 20 age- and sex-matched healthy controls.

RESULTS

Serum levels of total PC (q-value 0.01), total SM (q-value 0.0002) were significantly lower, and total acylcarnitines (q-value 0.02) were significantly higher in patients than in controls. After normalisation of data, serum levels of 12 PC and 1 SM Fontan patients were significantly lower (q-values <0.05), and concentrations of 3 acylcarnitines were significantly higher than those in controls (q-values <0.05).

CONCLUSION

Metabolomic profiling can use small specimens to identify biomarker patterns that track derangement in multiple metabolic pathways. The striking alterations in the phospholipid and acylcarnitine metabolome that we found in Fontan patients may reflect altered cell signalling and metabolism as found in heart failure in biventricular patients, chronic low-level inflammation, and alteration of functional or structural properties of lymphatic or blood vessels.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Identifier NCT03886935.

Impact of the Fontan Operation on Organ Systems

In patients having undergone the Fontan operation, besides the well discussed changes in the cardiac, pulmonary and gastrointestinal system, alterations of further organ systems including the hematologic, immunologic, endocrinological and metabolic are reported. As a medical adjunct to Fontan surgery, the systematic study of the central role of the liver as a metabolizing and synthesizing organ should allow for a better understanding of the pathomechanism underlying the typical problems in Fontan patients, and in this context, the profiling of endocrinological and metabolic patterns might offer a tool for the optimization of Fontan follow-up, targeted monitoring and specific adjunct treatment.