Body Composition in Young Adults Living With a Fontan Circulation: The Myopenic Profile

Percentage Predicted Peak Oxygen Consumption in People With Fontan Circulation: A Rapid Systematic Scoping Review and Validation Study

BACKGROUND

Peak oxygen consumption (peak V ̇ O 2 $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ ) is routinely measured in people who have congenital heart disease and is reported as a percentage of predicted value, based upon age- and sex-matched normative reference values (NRVs). This study aimed to identify which NRVs are being used, assess whether NRVs are being applied appropriately, and evaluate if recommended NRVs are valid when applied to people with congenital heart disease.

METHODS AND RESULTS

A systematic scoping review identified studies that reported peak V ̇ O 2 $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ percentage of predicted value in people with congenital heart disease. A modified risk of bias tool evaluated the included studies. Forty-five studies reported peak V ̇ O 2 $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ percentage of predicted value, and only 21 (47%) studies described or provided a reference on how their percentage of predicted value was calculated. The most cited NRVs were from Wasserman (n=12) and Cooper and Weiler-Ravell (n=7). Risk of bias analysis judged 63% of studies as having some concerns. The NRVs recommended by the American Heart Association were applied to participants with a Fontan circulation (n=70; aged 26.5±6.4 years; 59% women) to examine validity. Predicted peak V ̇ O 2 $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ values from the Wasserman NRV was not significantly associated to measured peak V ̇ O 2 $$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ values (men: b=0.31, R2≤0.01; women: b=0.07, R2=0.02).

CONCLUSIONS

Numerous NRVs have been applied to individuals with congenital heart disease and are often poorly reported and inappropriately matched to participants. The Wasserman NRV was the most cited but showed poor validity when applied to a Fontan cohort.

Advances in Diagnostic and Interventional Catheterization in Adults with Fontan Circulation

Over the past five decades, the Fontan procedure has been developed to improve the life expectancy of patients with congenital heart defects characterized by a functionally single ventricle. The Fontan circulation aims at redirecting systemic venous return to the pulmonary circulation in the absence of an impelling subpulmonary ventricle, which makes this physiology quite fragile and leads to several long-term complications. Despite the importance of hemodynamic assessment through cardiac catheterization in the management and follow-up of these patients, a thorough understanding of the ultimate functioning of this type of circulation is lacking, and the interpretation of the hemodynamic data is often complex. In recent years, new tools such as combined catheterization with cardiopulmonary exercise testing have been incorporated to improve the understanding of the hemodynamic profile of these patients. Furthermore, extensive percutaneous treatment options have been developed, addressing issues ranging from obstructive problems in Fontan pathway and acquired shunts through compensatory collaterals to the percutaneous treatment of lymphatic circulation disorders and transcatheter edge-to-edge repair of atrioventricular valves. The aim of this review is to detail the various tools used in cardiac catheterization for patients with Fontan circulation, analyze different percutaneous treatment strategies, and discuss the latest advancements in this field.

Low pre-albumin but not thiamine predicts cognitive deficits in adolescents post-Fontan and healthy controls

BACKGROUND

Low pre-albumin, body mass index, and thiamine levels have been associated with poor nutritional status and cognitive/memory deficits in adult heart failure patients. However, the relationship of these nutritional/dietary intake biomarkers to cognition has not been assessed in adolescents post-Fontan procedure and healthy controls.

METHODS

This is a cross-sectional study. Adolescents (14-21 years of age) post-Fontan completion were recruited from paediatric cardiology clinics and controls from the community. The Montreal Cognitive Assessment was administered (normal ≥ 26), and blood draw (thiamine [normal 70-110 nmol/L] and pre-albumin levels [adolescent normal 23-45 mg/dL]) and the Thiamine Food Frequency Questionnaire were completed by all participants.

RESULTS

Seventy subjects, 40 post-Fontan (mean age 16 ± 1.6, female 51%, Hispanic 44%, hypoplastic left heart syndrome 26%) and 30 controls (mean age 16.8 ± 1.9, female 52%, Hispanic 66%), were participated. Post-Fontan group had lower median total cognitive scores (23 versus 29, p < 0.001), pre-albumin levels (23 versus 27, p = 0.013), and body mass index (20 versus 24, p = 0.027) than controls. Post-Fontan group had higher thiamine levels than controls (127 versus 103, p = 0.033). Lower pre-albumin levels (< 23) and underweight body mass index were associated with abnormal total cognitive scores (p = 0.030). Low pre-albumin level (p = .038) was an independent predictor of worse cognition.

CONCLUSION

Lower pre-albumin was an independent predictor for worse cognition in adolescents post-Fontan. Lower pre-albumin levels may reflect chronic liver changes or protein-losing enteropathy seen in Fontan physiology. These findings highlight the possibility for nutrition-induced cognitive changes.

Cardiovascular Imaging-Derived Skeletal Muscle Mass Correlates With Fitness and Survival in Patients With Univentricular Circulation

Aims This study aims to retrospectively quantify skeletal muscle mass from cardiovascular imaging studies in total cavopulmonary connection (TCPC) patients and to correlate calculated muscle mass with clinical outcomes. Materials and methods Ninety-one TCPC patients at a mean age of 24.0 ±5.5 years (37 women; 40.7%) who underwent chest computed tomography (CT) or cardiac magnetic resonance imaging (MRI) as part of their follow-up were identified in a single-center database. The cross-sectional skeletal muscle index (SMI) at the Th4 and Th12 levels was calculated from CT images, and the dorsal skeletal muscle area (SMA) at the Th12 level was measured from an MRI. Results Calculated SMI at Th12 level was 38.0 (34.5; 42.0) cm2.m-2 or 89.6 (81.9; 101.6) % of predicted values. The median follow-up from CT was 5.9 (3.1; 8.5) years, and the composite endpoint (death N=5, heart transplant N=6) was reached in a total of 11 (26.8%) patients. Patients with SMI (Th12) less than 90% of predicted values had a hazard ratio of 5.8 (95% CI: 1.2; 28.3) (p=0.03) for endpoint achievement. In the MRI group, dorsal SMA at the Th12 level was 27.6 ±5.1 cm2 in men and 20.0 ±5.8 cm2 in women. Correlations were found between SMA/kg and peak oxygen uptake (VO2 peak) (r=0.48, p=0.0005) and fat-free mass (r=0.63, p<0.0001), respectively. Conclusions A low SMI at the Th12 level was associated with a higher risk of death or cardiac transplantation. Evaluation of skeletal muscle mass using cardiovascular imaging methods allows rapid identification of individuals at risk of sarcopenia.

Association of albuminuria with kidney function and hemodynamic disturbance in pre-school children who undergo congenital heart disease surgery

BACKGROUND

We validated the prevalence of albuminuria and its association with kidney function and hemodynamics in pre-school children who underwent surgery for congenital heart disease (CHD).

METHODS

From 403 patients who had undergone surgery for CHD at least 6 months before pre-school and were admitted to our hospital between 2011 and 2015, 75 who underwent blood and urine tests and cardiac catheterization were included in this study. The urinary albumin-to-creatinine ratio (ACR) was quantified, and the relationship of ACR with physical and laboratory findings and hemodynamics assessed using cardiac catheterization was analyzed.

RESULTS

The study cohort was divided into three groups: Fontan group (n = 25), tetralogy of Fallot (TOF) group (n = 18), and control group (other biventricular CHDs; n = 32). The median age of patients was 5.9 years. ACR was higher in the Fontan group than in the TOF and control groups (median: 15.0 vs. 5.0 and 0.0 mg/g, p < 0.001). Moreover, albuminuria (ACR > 30 mg/g) was observed in 20.0% of Fontan patients, while ACR was associated with potential complicating factors of Fontan circulation: high central venous pressure, high mean pulmonary artery pressure, and worse than moderate atrioventricular regurgitation. ACR showed a moderate correlation with the cystatin C-based estimated glomerular filtration rate (r =  - 0.725, p < 0.001).

CONCLUSIONS

Measurement of albuminuria in Fontan patients before they join elementary school is useful because it reflects kidney function and hemodynamic factors that can worsen their condition. Identification and management of patients with albuminuria may facilitate early therapeutic intervention for worsening Fontan factors, eventually delaying the deterioration of kidney function. A higher resolution version of the Graphical abstract is available as Supplementary information.

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.

Exploring the utility of bedside tests for predicting cardiorespiratory fitness in older adults

Objectives

Cardiorespiratory fitness (CRF) declines with advancing and has also, independent of age, been shown to be predictive of all-cause mortality, morbidity, and poor clinical outcomes. In relation to the older patient, there is a particular wealth of evidence highlighting the relationship between low CRF and poor surgical outcomes. Cardiopulmonary exercise testing (CPET) is accepted as the gold-standard measure of CRF. However, this form of assessment has significant personnel and equipment demands and is not feasible for those with certain age-associated physical limitations, including joint and cardiovascular comorbidities. As such, alternative ways to assess the CRF of older patients are very much needed.

Methods

Sixty-four participants (45% female) with a median age of 74 (65-90) years were recruited to this study via community-based advertisements. All participants completed three tests of physical function: (1) a step-box test; (2) handgrip strength dynamometry; and (3) a CPET on a cycle ergometer; and also had their muscle architecture (vastus lateralis) assessed by B-mode ultrasonography to provide measures of muscle thickness, pennation angle, and fascicle length. Multivariate linear regression was then used to ascertain bedside predictors of CPET parameters from the alternative measures of physical function and demographic (age, gender, body mass index (BMI)) data.

Results

There was no significant association between ultrasound-assessed parameters of muscle architecture and measures of CRF. VO2peak was predicted to some extent from fast step time during the step-box test, gender, and BMI, leading to a model that achieved an R 2 of 0.40 (p < 0.001). Further, in aiming to develop a model with minimal assessment demands (i.e., using handgrip dynamometry rather than the step-box test), replacing fast step time with non-dominant HGS led to a model which achieved an R 2 of 0.36 (p < 0.001). Non-dominant handgrip strength combined with the step-box test parameter of fast step time and BMI delivered the most predictive model for VO2peak with an R 2 of 0.45 (p < 0.001).

Conclusions

Our findings show that simple-to-ascertain patient characteristics and bedside assessments of physical function are able to predict CPET-derived CRF. Combined with gender and BMI, both handgrip strength and fast step time during a step-box test were predictive for VO2peak. Future work should apply this model to a clinical population to determine its utility in this setting and to explore if simple bedside tests are predictive of important clinical outcomes in older adults (i.e., post-surgical complications).

Research Gaps in Pediatric Heart Failure: Defining the Gaps and Then Closing Them Over the Next Decade

Given the numerous opportunities and the wide knowledge gaps in pediatric heart failure, an international group of pediatric heart failure experts with diverse backgrounds were invited and tasked with identifying research gaps in each pediatric heart failure domain that scientists and funding agencies need to focus on over the next decade.

Body composition in patients with Fontan physiology: a systematic review

Fontan circulation is a highly abnormal circulatory state that may affect various organ systems. The effect on body composition is an important factor to assess the condition of the patient. This systematic review assesses body composition and possibly related adverse outcomes in patients with a Fontan circulation, to provide an overview of current insights. Studies evaluating body composition by compartment (either fat mass or lean/muscle mass) in Fontan patients published up to April 2023 were included in this systematic review. Of 1392 potential studies, 18 studies met the inclusion criteria. In total, body composition measurements of 774 Fontan patients were included. Body composition was measured using dual-energy X-ray absorptiometry (DXA) (n = 12), bioelectrical impedance analysis (BIA) (n = 5), computer tomography (CT) (n = 1), or magnetic resonance imaging (MRI) (n = 1). All studies reported a normal body mass index (BMI) in Fontan patients, compared to controls. Five out of nine studies reported significantly higher body fat values, and twelve out of fifteen studies reported significantly lower muscle or lean mass values in the Fontan population compared to the healthy population. Unfavorable body composition in Fontan patients was associated with decreased exercise capacity, worse cardiac function, and adverse outcomes including hospital admissions and death.   Conclusions: Despite having a normal BMI, Fontan patients have an increased fat mass and decreased muscle mass or lean mass compared to the healthy population. This unfavorable body composition was associated with various adverse outcomes, including a decreased exercise capacity and worse cardiac function. What is Known: • Patients with a Fontan circulation have a decreased exercise capacity compared to healthy peers, an unfavorable body composition might be a contributor to their impaired exercise capacity. What is New: • Fontan patients are predisposed to an unfavorable body composition, characterized by increased fat mass and decreased muscle mass accompanied by a normal BMI compared to the healthy population. • Among others, unfavorable body composition was associated with decreased exercise capacity, cardiac function, and increased morbidity in patients with a Fontan circulation.

Cluster Sets to Prescribe Interval Resistance Training: A Potential Method to Optimise Resistance Training Safety, Feasibility and Efficacy in Cardiac Patients

The integration of resistance training for cardiac patients leads to important health outcomes that are not optimally obtained with aerobic exercise; these include an increase in muscle mass, maintenance of bone mineral density, and improvements in muscular fitness parameters. Despite the proliferation of evidence supporting resistance exercise in recent decades, the implementation of resistance training is underutilised, and prescription is often sub-optimal in cardiac patients. This is frequently associated with safety concerns and inadequate methods of practical exercise prescription. This review discusses the potential application of cluster sets to prescribe interval resistance training in cardiac populations. The addition of planned, regular passive intra-set rest periods (cluster sets) in resistance training (i.e., interval resistance training) may be a practical solution for reducing the magnitude of haemodynamic responses observed with traditional resistance training. This interval resistance training approach may be a more suitable option for cardiac patients. Additionally, many cardiac patients present with impaired exercise tolerance; this model of interval resistance training may be a more suitable option to reduce fatigue, increase patient tolerance and enhance performance to these workloads. Practical strategies to implement interval resistance training for cardiac patients are also discussed. Preliminary evidence suggests that interval resistance training may lead to safer acute haemodynamic responses in cardiac patients. Future research is needed to determine the efficacy and feasibility of interval resistance training for health outcomes in this population.

Cardiac Function and Serum Biomarkers throughout Staged Fontan Palliation: A Prospective Observational Study

Fontan patients undergo multiple cardiothoracic surgeries in childhood. Following these procedures, ventricular function is temporarily decreased, and recovers over months. This is presumably related to cardiopulmonary bypass, but this is incompletely understood. Throughout the Fontan palliation, cardiac function is also affected by volume unloading. We aimed to gain insight into the biological processes related to impaired ventricular function and recovery following Fontan palliations using a panel of biomarkers. Furthermore, we described changes in ventricular function across the Fontan palliation due to volume unloading. We performed a prospective multicenter observational study in patients undergoing partial (PCPC) or total cavo-pulmonary connection (TCPC). Patients underwent assessment-including echocardiography and blood sampling-before surgery (T1), at first follow-up (T2), and 1 year after their procedures (T3). Blood samples were analyzed using a biomarker panel (OLINK CVD-III). Ninety-two biomarkers were expressed as principal components (PC) to limit multiple statistical testing. We included 32 PCPC patients aged 7.2 [5.3-10.3] months, and 28 TCPC patients aged 2.7 [2.2-3.8] years. The single ventricular longitudinal strain (SV GLS) temporarily decreased for PCPC patients at T2 (-15.1 ± 5.6 (T1) to -13.5 ± 5.2 (T2) to -17.3 ± 4.5 (T3), p < 0.047 for all differences), but not following TCPC. The serum biomarkers were expressed as 4 PCs. PC1, including biomarkers of cell-cell adhesion, was not related to any patient characteristic. PC2, including biomarkers of superoxide anion regulation, increased at T2. PC3, including biomarkers of cardiovascular development, related to the stage of Fontan palliation. PC4 was of uncertain biological or clinical significance. No PC was found that related to ventricular performance. The SV GLS was temporarily diminished following PCPC, but not following TCPC. Several biomarkers were related to post-operative stress and adaptation to the PCPC or TCPC circulation, but none were related to the outcome.

Sarcopenia and cardiovascular diseases: A systematic review and meta-analysis

Sarcopenia is an age-related disease and is often accompanied by other diseases. Now, many studies have shown that cardiovascular diseases (CVDs) may raise the incidence rate of sarcopenia. Therefore, the purpose of this study was to conduct a systematic review and meta-analysis to investigate the prevalence of sarcopenia in patients with CVDs compared with the general population, defined as relatively healthy non-hospitalized subjects. The databases of PubMed, Embase, Medline and Web of Science were searched for eligible studies published up to 12 November 2022. Two assessment tools were used to evaluate study quality and the risk of bias. Statistical analysis was conducted using STATA 14.0 and R Version 4.1.2. Thirty-eight out of the 89 629 articles retrieved were included in our review. The prevalence of sarcopenia ranged from 10.1% to 68.9% in patients with CVDs, and the pooled prevalence was 35% (95% confidence interval [95% CI]: 28-42%). The pooled prevalence of sarcopenia was 32% (95% CI: 23-41%) in patients with chronic heart failure (CHF), 61% (95% CI: 49-72%) in patients with acute decompensated heart failure (ADHF), 43% (95% CI: 2-85%) in patients with coronary artery disease, 30% (95% CI: 25-35%) in patients with cardiac arrhythmia (CA), 35% (95% CI: 10-59%) in patients with congenital heart disease and 12% (95% CI: 7-17%) in patients with unclassed CVDs. However, in the general population, the prevalence of sarcopenia varied from 2.9% to 28.6% and the pooled prevalence was 13% (95% CI: 9-17%), suggesting that the prevalence of sarcopenia in patients with CVDs was about twice compared with the general population. The prevalence of sarcopenia was significantly higher only in patients with ADHF, CHF and CA compared with the general population. There is a positive correlation between CVDs and sarcopenia. The prevalence of sarcopenia is higher in patients with CVDs than that in the general population. With global aging, sarcopenia has brought a heavy burden to individuals and society. Therefore, it is important to identify the populations with high-risk or probable sarcopenia in order to do an early intervention, such as exercise, to counteract or slow down the progress of sarcopenia.

Surrogates of Muscle Mass on Cardiac MRI Correlate with Exercise Capacity in Patients with Fontan Circulation

BACKGROUND

Sarcopenia is an increasingly recognized marker of frailty in cardiac patients. Patients with a history of congenital heart disease and Fontan procedure have a higher risk of developing progressive muscle wasting. Our objective was to determine if we could use routine cardiac MRI (CMR) for the surveillance of muscle wasting.

METHODS

A retrospective study of all Fontan patients (n = 75) was conducted at our institution, with CMR performed from 2010 to 2022 and exercise stress testing performed within 12 months (4.3 ± 4.2 months). The skeletal muscle area (SMA) for the posterior paraspinal and anterior thoracic muscles were traced and indexed for body surface area (BSA). Patients were stratified by percentile into the upper and lower quartiles, and the two groups were compared. Multivariable regression was performed to control for sex and age.

RESULTS

There was a significant positive association of both anterior (r = 0.34, p = 0.039) and paraspinal (r = 0.43, p = 0.007) SMA to peak VO2. Similarly, paraspinal but not anterior SMA was negatively associated with the VE/VCO2 (r = -0.45, p = 0.006). The upper quartile group had significantly more males (18/19 vs. 8/20; p = 0.0003) and demonstrated a significantly higher peak VO2 (32.2 ± 8.5 vs. 23.8 ± 4.7, p = 0.009), a higher peak RER (1.2 ± 0.1 vs. 1.1 ± 0.04, p = 0.007), and a significantly lower VE/VCO2 (32.9 ± 3.6 vs. 40.2 ± 6.2, p = 0.006) compared to the lowest quartile. The association of SMA to VO2 peak and VE/VCO2 was redemonstrated after controlling for sex and age.

CONCLUSION

Thoracic skeletal muscle area may be an effective surrogate of muscle mass and is correlated to several measures of cardiorespiratory fitness post-Fontan. CMR would be an effective tool for the surveillance of sarcopenia in post-Fontan patients given its accessibility and routine use in these patients.

Assessment of exercise capacity using field walking tests in patients after the Fontan procedure: A case-control study

BACKGROUND

Despite the frequent use of the 6-minute walk test (6MWT), exercise capacity has not been assessed with the incremental shuttle walk test (ISWT) in patients who have undergone the Fontan procedure. It is unclear whether these tests cause clinically relevant cardiorespiratory responses in these patients.

OBJECTIVES

We aimed to assess cardiorespiratory responses to the 6MWT and ISWT in Fontan patients, compare the responses with those in the controls, and examine the agreement between the two field tests.

METHODS

Submaximal exercise capacity was assessed using the 6MWT, maximal exercise capacity using the ISWT, quadriceps isometric muscle strength with a hand dynamometer, and body composition using a bioelectrical impedance device.

RESULTS

Twenty-one Fontan patients (16.42±6.63 years, 5F/16M) and 21 controls (16.57±4.30 years, 7F/14M) were included. While body composition was similar between the groups (p>0.05), quadriceps isometric muscle strength and 6MWT and ISWT distance were lower in the Fontan patients than in the controls (p<0.05). In both the 6MWT and ISWT, pre- and post-test heart rate (HR), oxygen saturation (SpO₂), dyspnea, and leg fatigue differed significantly between the Fontan patients and the controls (p<0.05). In addition, the ISWT resulted in a more significant change in HR, SpO₂, and leg fatigue than the 6MWT in the Fontan patients (p<0.05). Bland-Altman plots for the 6MWT vs. the ISWT indicated agreement between the two tests.

CONCLUSION

There were remarkable changes in HR, SpO₂, dyspnea, and leg fatigue in both tests. With similar safety to the 6MWT but with more caution applied for adverse events, the ISWT can also be performed as a field test to evaluate exercise capacity and identify more pronounced exercise-induced responses (especially oxygen desaturation) in Fontan patients.

Somatic growth in single ventricle patients: A systematic review and meta-analysis

AIM

To map somatic growth patterns throughout Fontan palliation and summarise evidence on its key modifiers.

METHODS

Databases were searched for relevant articles published from January 2000 to December 2021. Height and weight z scores at each time point (birth, Glenn procedure, Fontan procedure and >5 years after Fontan completion) were pooled using a random effects meta-analysis. A random effects meta-regression model was fitted to model the trend in z scores over time.

RESULTS

Nineteen studies fulfilled eligibility criteria, yielding a total of 2006 participants. The z scores for height and weight were markedly reduced from birth to the interstage period, but recovered by about 50% following the Glenn procedure. At >10 years after the Fontan procedure, the z scores for weight seemed to normalise despite persistent lower height, resulting in increased body mass index. The review revealed a number of modifiers of somatic growth, including aggressive nutritional management, timing of Glenn/Fontan, prompt resolution of complications and obesity prevention programmes in adolescence and adulthood.

CONCLUSION

This review mapped the somatic growth of single ventricle patients and summarised key modifiers that may be amendable to improvement. These data provide guidance on strategies to further optimise somatic growth in this population and may serve as a benchmark for clinical follow-up.

Prolonged Enteral Tube Feeding in Infants With a Functional Single Ventricle Is Associated With Adverse Outcomes After Fontan Completion

OBJECTIVES

To define the baseline characteristics of long-term tube-fed single ventricle patients, investigate associations between long-term enteral tube feeding and growth, and determine associations with long-term outcomes after Fontan procedure.

STUDY DESIGN

We performed a retrospective cohort study of patients in the Australia and New Zealand Fontan Registry undergoing treatment at the Royal Children's Hospital, the Children's Hospital at Westmead, Royal Melbourne Hospital, and Royal Prince Alfred Hospital from 1981-2018. Patients were defined as tube-fed (TF) or non-tube-fed (NTF) based on enteral tube feeding at age 90 days. Feeding groups were compared regarding BMI trajectory, BMI at last follow-up, and long-term incidence of severe Fontan failure.

RESULTS

Of 390 patients (56(14%) TF, 334(86%) NTF), TF was associated with right ventricular dominance, hypoplastic left heart syndrome, Norwood procedure, increased procedures prior to Fontan, extracardiac conduit Fontan, Fontan fenestration, and atrioventricular valve repair/replacement. TF patients were less likely to be in the higher compared with lowest 0-6 month BMI trajectory (P<0.01,P=0.03), had lower 6month weight-for-age z-scores (P<0.01) and length-for-age z-scores (P=0.01). TF were less likely to be overweight/obese at pediatric follow-up (HR=0.31,95%CI:0.12-0.80;P=0.02) and more likely to be underweight at adult follow-up ((HR=16.51; 5%CI:2.70-101.10;P<0.01).TF compared with NTF was associated with increased risk of severe Fontan failure (HR=4.13;95%CI=1.65,10.31;P<0.01).

CONCLUSIONS

Prolonged infant enteral tube feeding is an independent marker of poor growth and adverse clinical outcomes extending long-term post-Fontan procedure.

Exercise as therapy for neurodevelopmental and cognitive dysfunction in people with a Fontan circulation: A narrative review

People with a Fontan circulation are at risk of neurodevelopmental delay and disability, and cognitive dysfunction, that has significant implications for academic and occupational attainment, psychosocial functioning, and overall quality of life. Interventions for improving these outcomes are lacking. This review article discusses current intervention practices and explores the evidence supporting exercise as a potential intervention for improving cognitive functioning in people living with a Fontan circulation. Proposed pathophysiological mechanisms underpinning these associations are discussed in the context of Fontan physiology and avenues for future research are recommended.

Scaling Peak Oxygen Consumption for Body Size and Composition in People With a Fontan Circulation

Background Peak oxygen consumption (peak V̇O2$$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$) is traditionally divided ("ratio-scaled") by body mass (BM) for clinical interpretation. Yet, it is unknown whether ratio-scaling to BM can produce a valid size-independent expression of peak V̇O2$$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ in people with a Fontan circulation. Furthermore, people with a Fontan circulation have deficits in lean mass, and it is unexplored whether using different measures of body composition may improve scaling validity. The objective was to assess the validity of different scaling denominators (BM, stature, body surface area, fat-free mass, lean mass, and appendicular lean mass using ratio and allometric scaling). Methods and Results Eighty-nine participants (age: 23.3±6.7 years; 53% female) with a Fontan circulation had their cardiorespiratory fitness and body composition measured by cardiopulmonary exercise testing and dual-energy x-ray absorptiometry. Ratio and allometric (log-linear regression) scaling was performed and Pearson correlations assessed scaling validity. Scaling denominators BM (r=-0.25, P=0.02), stature (r=0.46, P<0.001), and body surface area (0.23, P=0.03) were significantly correlated with their respective ratio-scaled expressions of peak V̇O2$$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$, but fat-free mass, lean mass, or appendicular lean mass were not (r≤0.11; R²=1%). Allometrically expressed peak V̇O2$$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ resulted in no significant correlation with any scaling denominator (r=≤0.23; R²=≤4%). Conclusions The traditional and accepted method of ratio-scaling to BM is invalid because it fails to create a size-independent expression of peak V̇O2$$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ in people with a Fontan circulation. However, ratio-scaling to measures of body composition (fat-free mass, lean mass, and appendicular lean mass) and allometric techniques can produce size-independent expressions of peak V̇O2$$ \dot{\mathrm{V}}{\mathrm{O}}_2 $$ in people with a Fontan circulation.

Safety and efficacy of exercise training in children and adolescents with congenital heart disease: A systematic review and descriptive analysis

BACKGROUND

While exercise training is beneficial in the prevention and management of many chronic diseases, the role of exercise training in children and adolescents with congenital heart disease is less understood. We sought to determine the safety and efficacy of exercise training in children and adolescents with congenital heart disease.

METHODS

We conducted a systematic search of the following databases: PubMed, CINAHL, EMBASE, Web of Science and SportDiscus. We included randomised controlled trials that incorporated an exercise intervention compared with a non-exercising comparator group and examined safety and efficacy in children and adolescents with congenital heart disease. A descriptive analysis of the included trials was then conducted.

RESULTS

A total of 9 articles from 6 trials (642 participants with varying conditions and disease severity) were included. Significant variability of study participants and outcomes were observed across the trials. No adverse events linked to the exercise interventions were stated. The articles reported numerous positive changes to clinically relevant fitness measures. Exercise capacity improved with exercise training in 3 of 4 trials in which it was measured. Cardiorespiratory fitness showed improvements in 3 of 4 trials. Neuromuscular fitness increased in 1 of 2 trials. Physiological and metabolic parameters were improved, and negative changes were not observed to several clinically important measures (e.g. muscular oxygenation, cardiac measures) in 2 of 2 trials. Physical activity increased in 1 of 3 trials. No articles reported on changes in measures of body composition. Outcomes are varied with little consensus on measurements or assessment methods.

CONCLUSIONS

Exercise training appears to be safe and efficacious for improving physical fitness in children and adolescents with congenital heart disease who have been appropriately screened by their medical team. However, the certainty of the evidence for these findings is low to moderate.

Association Between Anthropometric Indices and Skeletal-Muscle Atrophy in Chinese Patients with Stable Chronic Obstructive Pulmonary Disease: A Cross-Sectional Study

Purpose

Anthropometric indices are simple indicators of patient nutritional status. However, the association between these indices and skeletal-muscle atrophy in patients with stable chronic obstructive pulmonary disease (COPD) has not been fully investigated. In this study, we evaluated this association.

Patients and Methods

We recruited 123 outpatients with stable COPD from a general hospital in China from 2020 to 2021. We recorded their demographic characteristics, including age, sex, course of illness, dyspnea score, body mass index (BMI), force expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), smoking status, and severity grading. In addition, patients' anthropometric indices, including fat-free mass index (FFMI) and appendicular skeletal-muscle mass index (ASMI), were measured using a body composition analyzer, and measurements were taken of the triceps skinfold (TSF), midarm circumference (MAC), and calf circumference (CC). We drew and analyzed a receiver operating characteristic (ROC) curve to identify the best intercept point value for the assessment of skeletal-muscle atrophy.

Results

The TSF, MAC, CC, FFMI, and ASMI of COPD patients were 1.08 ± 0.44 cm, 26.39 ± 2.92 cm, 34.5 ± 3.06 cm, 17.49 ± 1.86 kg/m², and 8.17 ± 0.90 kg/m², respectively. These anthropometric indices had a significant positive correlation with skeletal-muscle mass (correlation values, 0.481-0.820). CC was strongly correlated with both FFMI and ASMI. The ROC curve showed an area-under-the-curve (AUC) value of 0.873-0.959.

Conclusion

Anthropometric indices were correlated with skeletal-muscle mass. CC showed the best diagnostic value in COPD patients, suggesting its effectiveness as a simple method for assessing skeletal-muscle atrophy and identifying patients with a noticeable reduction in muscle mass. Such patients require early, multidisciplinary intervention.

Nutritional Management of Patients with Fontan Circulation: A Potential for Improved Outcomes from Birth to Adulthood

Fontan circulation (FC) is a surgically achieved palliation state offered to patients affected by a wide variety of congenital heart defects (CHDs) that are grouped under the name of univentricular heart. The procedure includes three different surgical stages. Malnutrition is a matter of concern in any phase of life for these children, often leading to longer hospital stays, higher mortality rates, and a higher risk of adverse neurodevelopmental and growth outcomes. Notwithstanding the relevance of proper nutrition for this subset of patients, specific guidelines on the matter are lacking. In this review, we aim to analyze the role of an adequate form of nutritional support in patients with FC throughout the different stages of their lives, in order to provide a practical approach to appropriate nutritional management. Firstly, the burden of faltering growth in patients with univentricular heart is analyzed, focusing on the pathogenesis of malnutrition, its detection and evaluation. Secondly, we summarize the nutritional issues of each life phase of a Fontan patient from birth to adulthood. Finally, we highlight the challenges of nutritional management in patients with failing Fontan.

Body Mass Index Trajectory and Outcome Post Fontan Procedure

Background Patients with a single ventricle who experience early life growth failure suffer high morbidity and mortality in the perisurgical period. However, long-term implications of poor infant growth, as well as associations between body mass index (BMI) and outcome in adulthood, remain unclear. We aimed to model BMI trajectories of patients with a single ventricle undergoing a Fontan procedure to determine trajectory-based differences in baseline characteristics and long-term clinical outcomes. Methods and Results We performed a retrospective analysis of medical records from patients in the Australia and New Zealand Fontan Registry receiving treatment at the Royal Children's Hospital, The Children's Hospital at Westmead, Royal Melbourne Hospital, and Royal Prince Alfred Hospital from 1981 to 2018. BMI trajectories were modeled in 496 patients using latent class growth analysis from 0 to 6 months, 6 to 60 months, and 5 to 16 years. Trajectories were compared regarding long-term incidence of severe Fontan failure (defined as mortality, heart transplantation, Fontan takedown, or New York Heart Association class III/IV heart failure). Three trajectories were found for male and female subjects at each age group-lower, middle, higher. Subjects in the lower trajectory at 0 to 6 months were more likely to have an atriopulmonary Fontan and experienced increased mortality long term. No association was found between higher BMI trajectory, current BMI, and long-term outcome. Conclusions Poor growth in early life correlates with increased long-term severe Fontan failure. Delineation of distinct BMI trajectories can be used in larger and older cohorts to find optimal BMI targets for patient outcome.

Sports participation, activity, and obesity in children who have undergone the Fontan procedure

BACKGROUND

Children with CHD are at risk for obesity and low levels of activity. These factors are associated with an increased risk of poor outcome. Participation in organised sports is an important avenue for children to maintain physical activity, though the relationship between sports participation and obesity has not been examined in the Fontan population.

METHODS

We performed a cross-sectional study of children aged 8-18 who had been evaluated between January 1, 2015 and October 1, 2019 at the Doernbecher Children's Hospital outpatient paediatric cardiology clinic and had previously undergone a Fontan. Patients were excluded if they were unable to ambulate independently or if they had undergone a heart transplant. Patient characteristics were recorded from the electronic medical record. Parents were interviewed via a telephone survey and asked to describe their child's activity levels and sports participation.

RESULTS

Our final cohort included 40 individuals, 74% were male. The overall prevalence of obesity (CDC BMI >95% for sex/age) in the cohort (23%) was significantly higher in non-athletes (33%) than athletes (0) (p = 0.02). There was no difference in cardiac complications or comorbidities between athletes and non-athletes. Athletes were more likely to meet daily activity recommendations (p = 0.05).

CONCLUSION

Fontan patients who do not participate in sports are significantly more likely to be obese and less likely to be active than those who do. This is the first study to demonstrate the association between competitive sports participation and decreased likelihood of obesity in the Fontan population.

Vitamin D, liver-related biomarkers, and distribution of fat and lean mass in young patients with Fontan circulation

INTRODUCTION/AIM

Young patients with Fontan circulation may have low serum 25-hydroxyvitamin D levels, an affected liver, and unhealthy body compositions. This study aimed to explore the association between vitamin D intake/levels, liver biomarkers, and body composition in young Fontan patients.

METHOD

We collected prospective data in 2017 to 2018, obtained with food-frequency questionnaires, biochemical analyses of liver biomarkers, and dual-energy X-ray absorptiometry scans in 44 children with Fontan circulation. Body compositions were compared to matched controls (n = 38). Linear regression analyses were used to investigate associations of biomarkers, leg pain, and lean mass on serum levels of 25-hydroxyvitamin D. Biomarkers were converted to z scores and differences were evaluated within the Fontan patients.

RESULTS

Our Fontan patients had a daily mean vitamin D intake of 9.9 µg and a mean serum 25-hydroxyvitamin D of 56 nmol/L. These factors were not associated with fat or lean mass, leg pain, or biomarkers of liver status. The Fontan patients had significantly less lean mass, but higher fat mass than controls. Male adolescents with Fontan circulation had a greater mean abdominal fat mass than male controls and higher cholesterol levels than females with Fontan circulation.

CONCLUSION

Vitamin D intake and serum levels were not associated with body composition or liver biomarkers in the Fontan group, but the Fontan group had lower lean mass and higher fat mass than controls. The more pronounced abdominal fat mass in male adolescents with Fontan circulation might increase metabolic risks later in life.

The Impact of Physical Activity Restrictions on Health-Related Fitness in Children with Congenital Heart Disease

Children with congenital heart disease (CHD) are often restricted from some types of physical activity (PA) despite the lack of evidence regarding the need to restrict recreational PA, apart from those with rhythm disorders. This study retrospectively investigated the associations between parent-reported activity restrictions (on-going need to restrict exertion, body contact or competition) and measures of health-related fitness among 236 children (8.2 ± 2.1 years, range 4−12 years) treated for single ventricle (n = 104), tetralogy of Fallot (n = 48), transposition of the great arteries (n = 47) or atrial septal defect (n = 37). Body mass index (BMI), moderate-to-vigorous physical activity (MVPA; 7 day accelerometry), strength, flexibility, and movement skill assessment results were collected from the baseline assessment research records for two studies completed in Ontario, Canada. A subset of 62 children also had physician-reported activity restrictions. Regression models empirically tested the goodness of fit between the dependent and independent variables. Participants with body contact restrictions from both parents and physicians had significantly higher BMI z-scores (0.23 ± 1.19 vs. −0.32 ± 0.85; t = 2.55; p = 0.04 and 0.66 ± 1.33 vs. −0.02 ± 0.98; t = 2.25; p = 0.02 for CDC and WHO scores, respectively). Otherwise, BMI z-score was not associated with patient variables (p > 0.36; sex, cardiac diagnosis, age, or activity restriction). Children with any type of parent-reported restriction (0.98 ± 2.06 vs. −0.08 ± 1.99; t = 3.77; p = 0.0002) were less flexible. Movement skill (TGMD-2) scores were 50% lower (25.1 ± 31.2 vs. 52.6 ± 28.6; F = 6.93; p = 0.009) among children with parent-reported competitive sport restrictions. Weekly MVPA (p > 0.18) and strength (p > 0.05) were not associated with activity restriction. Children whose parents reported PA restrictions were less flexible, and had decreased movement skill and increased BMI z-scores if the restrictions impacted competitive sport or body contact, respectively. Future research is recommended to confirm these results among larger samples of children who have both parent- and physician-specified PA restrictions.

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.

Exercise Training for People Living with a Fontan Circulation: An Underutilized Intervention

Surgical repair for children born with single ventricle congenital heart disease, culminating in the Fontan operation, has resulted in dramatic improvements in survival; children born with these lesions are now typically expected to survive well into adulthood. Most, but not all, individuals with a Fontan circulation have reduced exercise capacity compared with the general population that in turn is associated with increased cardiovascular morbidity and mortality. The cause of reduced exercise capacity is multifactorial. A significant contributor is the absence of a subpulmonary ventricular pump, which limits preload and appropriate cardiac output augmentation to meet the increased metabolic demands that occur with exercise. While in its infancy relative to adults with acquired heart disease, the evidence to date suggests that exercise interventions to improve exercise capacity and Fontan physiology in children and adults with Fontan circulation are safe, effective and well tolerated. However, many knowledge gaps remain, including a detailed understanding of the unique physiological adaptations that occur, the optimal approach to exercise in this population and the effectiveness of home-based interventions utilizing telemedicine and remote physiologic monitoring technologies. Furthermore, the long-term impact of such interventions on the Fontan-cardiovascular system, physical activity levels, health-related quality of life, and late cardiovascular morbidity and mortality are not well characterized. In this review, we outline the factors associated with reduced exercise capacity in individuals with Fontan circulation, review the experience to date of dedicated interventions to improve exercise capacity, and highlight the current knowledge gaps in the field and priorities for further study.

The "Super-Fontan" Phenotype: Characterizing Factors Associated With High Physical Performance

Background: People with a Fontan circulation usually have moderately impaired exercise performance, although a subset have high physical performance ("Super-Fontan"), which may represent a low-risk phenotype. Methods: People with a "Super-Fontan" phenotype were defined as achieving normal exercise performance [≥80% predicted peak oxygen uptake (VO₂) and work rate] during cardiopulmonary exercise testing (CPET) and were identified from the Australian and New Zealand Fontan Registry. A Fontan control group that included people with impaired exercise performance (<80% predicted VO₂ or work rate) was also identified based on a 1:3 allocation ratio. A subset of participants were prospectively recruited and completed a series of physical activity, exercise self-efficacy, and health-related quality of life questionnaires. Results: Sixty CPETs ("Super-Fontan", n = 15; control, n = 45) were included. A subset ("Super-Fontan", n = 10; control, n = 13) completed a series of questionnaires. Average age was 29 ± 8 years; 48% were males. Exercise capacity reflected by percent predicted VO₂ was 67 ± 17% in the entire cohort. Compared to the "Super-Fontan" phenotype, age at Fontan completion was higher in controls (4.0 ± 2.9 vs. 7.2 ± 5.3 years, p = 0.002). Only one (7%) person in the "Super-Fontan" group had a dominant right ventricle compared to 15 (33%) controls (p = 0.043). None of those in the "Super-Fontan" group were obese, while almost a quarter (22%) of controls were obese based on body mass index (p = 0.046). Lung function abnormalities were less prevalent in the "Super-Fontan" group (20 vs. 70%, p = 0.006). Exercise self-efficacy was greater in the "Super-Fontan" group (34.2 ± 3.6 vs. 27.9 ± 7.2, p = 0.02). Self-reported sports participation and physical activity levels during childhood and early adulthood were higher in the "Super-Fontan" group (p < 0.05). The total average time spent participating in structured sports and physical activity was 4.3 ± 2.6 h/wk in the "Super-Fontan" group compared to 2.0 ± 3.0 h/wk in controls, p = 0.003. There were no differences in self-reported current total physical activity score or health-related quality of life between groups (p ≥ 0.05). Conclusions: The "Super-Fontan" phenotype is associated with a healthy weight, lower age at Fontan completion, better exercise self-efficacy, and higher overall levels of sport and physical activity participation during physical development.

Deficits in the Functional Muscle-Bone Unit in Youths with Fontan Physiology

OBJECTIVE

To determine whether dual energy X-ray absorptiometry (DXA), a clinically available tool, mirrors the magnitude of deficits in trabecular and cortical bone mineral density (BMD) demonstrated on peripheral quantitative computed tomography in youth with Fontan physiology.

STUDY DESIGN

We aimed to describe DXA-derived BMD at multiple sites and to investigate the relationship between BMD and leg lean mass, a surrogate for skeletal muscle loading. Subjects with Fontan (n = 46; aged 5-20 years) underwent DXA in a cross-sectional study of growth and bone and muscle health as described previously. Data from the Bone Mineral Density in Childhood Study were used to calculate age-, sex-, and race-specific BMD z-scores of the whole body, lumbar spine, hip, femoral neck, distal one-third radius, ultradistal radius, and leg lean mass z-score (LLMZ).

RESULTS

Fontan BMD z-scores were significantly lower than reference at all sites-whole body, -0.34 ± 0.85 (P = .01); spine, -0.41 ± 0.96 (P = .008); hip, -0.75 ± 1.1 (P < .001); femoral neck, -0.73 ± 1.0 (P < .001); distal one-third radius, -0.87 ± 1.1 (P < .001); and ultradistal radius. -0.92 ± 1.03 (P < .001)-as was LLMZ (-0.93 ± 1.1; P < .001). Lower LLMZ was associated with lower BMD of the whole body (R² = 0.40; P < .001), lumbar spine (R² = 0.16; P = .005), total hip (R² = 0.32; P < .001), femoral neck (R² = 0.47; P < .001), and ultradistal radius (R² = 0.35; P < .001).

CONCLUSIONS

Patients with Fontan have marked deficits in both cortical (hip, distal one-third radius) and trabecular (lumbar spine, femoral neck, ultradistal radius) BMD. Lower LLMZ is associated with lower BMD and may reflect inadequate skeletal muscle loading. Interventions to increase muscle mass may improve bone accrual.

Hepatic Steatosis in Patients With Single Ventricle and a Fontan Circulation

Background

Hepatic steatosis, caused by nonalcoholic fatty liver disease, is a leading cause of chronic liver disease. The interplay between hepatic steatosis and the development of liver disease following the Fontan procedure is not well understood. This study examined the prevalence and associations of hepatic steatosis in patients with a Fontan circulation.

Methods and Results

This was a single‐center retrospective study of 95 patients with a Fontan circulation with liver magnetic resonance imaging performed between 2012 and 2019. The average age at magnetic resonance imaging was 21.5±8.5 years. The percent liver fat signal was determined using magnetic resonance chemical shift‐encoded proton density fat fraction imaging. Hepatic steatosis was defined as liver fat ≥5% and was present in 10.5% of the cohort. The presence of hepatic steatosis was associated with higher body mass index (29±4 versus 24±6 kg/m², P=0.006), a higher frequency of obesity (50% versus 12%, P=0.015), lower high‐density lipoprotein cholesterol (35±9 versus 43±14 mg/dL, P=0.050), and greater subcutaneous fat thickness (2.6±0.7 versus 1.8±1.0 cm, P=0.043). There was no association between hepatic steatosis and cardiovascular imaging or hemodynamic variables from cardiac catheterization.

Conclusions

Risk factors for hepatic steatosis in patients with Fontan circulation include obesity and dyslipidemia, similar to what is seen in the general population. Fontan hemodynamics were not associated with hepatic steatosis.

Exercise Intolerance, Benefits, and Prescription for People Living With a Fontan Circulation: The Fontan Fitness Intervention Trial (F-FIT)-Rationale and Design

Background: Despite developments in surgical techniques and medical care, people with a Fontan circulation still experience long-term complications; non-invasive therapies to optimize the circulation have not been established. Exercise intolerance affects the majority of the population and is associated with worse prognosis. Historically, people living with a Fontan circulation were advised to avoid physical activity, but a small number of heterogenous, predominantly uncontrolled studies have shown that exercise training is safe-and for unique reasons, may even be of heightened importance in the setting of Fontan physiology. The mechanisms underlying improvements in aerobic exercise capacity and the effects of exercise training on circulatory and end-organ function remain incompletely understood. Furthermore, the optimal methods of exercise prescription are poorly characterized. This highlights the need for large, well-designed, multi-center, randomized, controlled trials. Aims and Methods: The Fontan Fitness Intervention Trial (F-FIT)-a phase III clinical trial-aims to optimize exercise prescription and delivery in people with a Fontan circulation. In this multi-center, randomized, controlled study, eligible Fontan participants will be randomized to either a 4-month supervised aerobic and resistance exercise training program of moderate-to-vigorous intensity followed by an 8-month maintenance phase; or usual care (control group). Adolescent and adult (≥16 years) Fontan participants will be randomized to either traditional face-to-face exercise training, telehealth exercise training, or usual care in a three-arm trial with an allocation of 2:2:1 (traditional:telehealth:control). Children (<16 years) will be randomized to either a physical activity and exercise program of moderate-to-vigorous intensity or usual care in a two-arm trial with a 1:1 allocation. The primary outcome is a change in aerobic exercise capacity (peak oxygen uptake) at 4-months. Secondary outcomes include safety, and changes in cardiopulmonary exercise testing measures, peripheral venous pressure, respiratory muscle and lung function, body composition, liver stiffness, neuropsychological and neurocognitive function, physical activity levels, dietary and nutritional status, vascular function, neurohormonal activation, metabolites, cardiac function, quality of life, musculoskeletal fitness, and health care utilization. Outcome measures will be assessed at baseline, 4-months, and 12-months. This manuscript will describe the pathophysiology of exercise intolerance in the Fontan circulation and the rationale and protocol for the F-FIT.

Impact of adiposity on clinical outcomes in people living with a Fontan circulation

BACKGROUND

To assess the association between body composition and the risk of adverse outcomes in Fontan patients.

METHODS

Participants from the Australian and New Zealand Fontan Registry with dual-energy X-ray absorptiometry scans were included. Appendicular lean mass (ALM), appendicular lean mass index (ALM divided by height squared; ALMI) and total body fat mass percentage (%BF) were calculated. ALMI and %BF z-scores were derived using age- and sex-matched reference ranges. The primary outcome was Fontan failure (death, transplantation, New York Heart Association functional class III/IV, protein-losing enteropathy, and plastic bronchitis) or moderate-or-severe ventricular dysfunction.

RESULTS

144 patients were included. Mean %BF was 29% (SD 10) with 50% having increased adiposity. Mean ALMI z-score was -1.4 (SD 1.1); one third of patients had skeletal muscle deficiency (ALMI z-score < -1 and -2) and another third had Fontan-associated myopaenia (ALMI z-score < -2). Age and %BF were associated with the risk of the endpoint in univariable regression (age: HR 1.09 per year, 95% CI 1.02-1.17, p = 0.01; %BF: HR 1.08, 95% CI 1.01-1.17, p = 0.03). On multivariable regression, every 1% increase in %BF was associated with a 10% increased risk of reaching the clinical endpoint (HR 1.10, 95% CI 1.01-1.19; p = 0.03). ALM was not associated with the endpoint (HR 1.02 per kg, 95% CI 0.88-1.20, p = 0.77).

CONCLUSIONS

Increased adiposity is associated with higher risk for adverse outcomes. Prospective studies to assess lifestyle interventions to optimise body composition should be prioritised.

Body Composition and Exercise Performance in Youth With a Fontan Circulation: A Bio-Impedance Based Study

Background Adults with a Fontan circulation tend to have myopenia and elevated adiposity when measured by dual energy x-ray absorptiometry. Bioelectrical impedance analysis is an alternative validated approach to assess body composition. We used bioelectrical impedance analysis to compare body composition between pediatric patients with a Fontan circulation and control individuals without heart disease. Methods and Results A retrospective chart review identified all patients aged <22 years with a Fontan circulation who presented for cardiopulmonary exercise testing and bioelectrical impedance analysis from April 2019 to January 2020. Data were compared with control subjects tested during the same period. We studied 47 patients with a Fontan circulation (53% boys; 15±3.1 years) and 165 controls (48% boys; 14.4±2.5 years). Fontan status was associated with shorter height, but similar age, sex, and overall body mass. Patients with Fontan had lower lean body mass (-12.0±22%, Z-score -0.5±1, P=0.005), skeletal muscle mass (-13.6±1.4%; Z-score, -0.5±1; P=0.004), skeletal muscle indexed to height (-10.3±13.3%; Z-score, -0.5±1; P=0.005), and higher percent body fat (+13.8±18.6%; Z-score, 0.4±1.2; P=0.03). Greater skeletal muscle mass was associated with higher peak oxygen consumption (r2=0.52, P<0.0001) and oxygen pulse (r2=0.68, P<0.0001). Patients who had suffered a late complication (ie, heart transplant referral or evidence of extracardiac organ dysfunction) of the Fontan operation (13 of 47, 27.7%) had lower skeletal muscle mass (P=0.048) and higher body fat percentage (P=0.003). Conclusions The Fontan circulation is associated with marked myopenia and increased adiposity. Higher muscle mass was associated with better exercise capacity. Fontan complications are associated with lower muscle mass and increased adiposity.

End-Organ Function and Exercise Performance in Patients With Fontan Circulation: What Characterizes the High Performers?

Background The physiologic hallmarks of the Fontan circulation-chronically elevated central venous pressures and low cardiac output-have significant effects not only on cardiovascular status but also impact other organ systems. Exercise capacity is limited in many and declines with age, accelerating in adolescence, but with wide variability. We explore the relationship between exercise performance and end-organ function in outpatient subjects with a Fontan circulation. Methods and Results This is a cross-sectional analysis of subject end-organ characterization from our outpatient Fontan circulation clinic with peak oxygen consumption (peak Vo₂) at cardiopulmonary exercise testing as the primary outcome. We perform linear regression to assess associations between clinical characteristics and peak Vo₂ as well as the magnitude of the association of clinical characteristics with peak Vo₂. Of 265 subjects age 12.8 (9.5-16.4) years, there is a negative correlation between age and peak Vo₂ (-0.49, P<0.001). Of those undergoing ramp cycle exercise testing, 34% perform above 80% predicted peak Vo₂. Variables positively associated with peak Vo₂ and their effect size include vitamin D sufficiency (+3.00, P=0.020) and absolute lymphocyte count (+0.23, P=0.005). Status as overweight/obese (-3.91, P=0.003) and hemoglobin (-0.77, P=0.003) are negatively associated. Neither ventricular morphology, timing of Fontan palliation, nor Fontan circulation type affect peak Vo₂. Conclusions Higher peak Vo₂ in those with a Fontan circulation is associated with younger age, vitamin D sufficiency, absence of overweight/obese, lower hemoglobin, and a healthier hepatic profile. Whether exercise training or other initiatives can modify organ characteristics in those with a Fontan circulation is worthy of exploration.

Body Composition in Young Adults Living With a Fontan Circulation: The Myopenic Profile

Background

We sought to characterize body composition abnormalities in young patients living with a Fontan circulation and explore potential pathophysiologic associations.

Methods and Results

Twenty‐eight patients with a Fontan circulation were prospectively recruited in this cross‐sectional study. Participants underwent cardiopulmonary exercise testing, dual‐energy X‐ray absorptiometry, echocardiography, and biochemical assessment. Mean age was 26±7 years. Skeletal muscle mass, estimated by appendicular lean mass index Z score, was reduced compared with reference data (−1.49±1.10, P<0.001). Percentage body fat Z score overall was within normal range (0.23±1.26, P=0.35), although 46% had elevated adiposity. Those with reduced skeletal muscle mass (appendicular lean mass index Z score of −1 or lower) had lower percent predicted oxygen pulse (55±15 versus 76±16%, P=0.002). Overall agreement between body mass index and dual‐energy X‐ray absorptiometry to assess adiposity was fair only (weighted [linear] κ coefficient: 0.53; 95% CI, 0.34–0.73) and slight in the setting of muscle mass deficiency (weighted κ coefficient: 0.32; 95% CI, 0.13–0.50). Appendicular lean mass was independently associated with absolute peak VO₂ (β=70.6 mL/min, P=0.001). Appendicular lean mass index Z score was inversely associated with hemoglobin (r=−0.4, P=0.04), and the degree of muscle deficit was associated with ventricular systolic impairment.

Conclusions

Young patients with a Fontan circulation have a body composition characterized by reduced skeletal muscle mass, which is associated with peak exercise capacity. Increased adiposity is common despite a normal body mass index. Low skeletal muscle mass is associated with systolic dysfunction and compensatory erythrocytosis.