Hemodynamics of Fontan Failure: The Role of Pulmonary Vascular Disease

Predictive utility of cardiac index-systemic vascular resistance plot and perfusion pressure in late post-Fontan patients

INTRODUCTION

Cases of Fontan failure with normal Fontan pressure have been reported. This study aimed to identify catheterisation-derived haemodynamic predictors of heart transplantation/death, other than Fontan pressure, in late post-Fontan patients.

METHODS

This retrospective study evaluated post-Fontan patients who underwent cardiac catheterisation at age ≥10 years between 1993 and 2018. The predictive effect of cardiac index-systemic vascular resistance index plot and perfusion pressure on freedom from the primary outcome (heart transplantation/death) was evaluated. Patients were categorised into haemodynamic categories A (cardiac index ≥ 3, systemic vascular resistance index ≥ 13), B (cardiac index < 3, systemic vascular resistance index ≥ 13), C (cardiac index ≥ 3, systemic vascular resistance index < 13), and D (cardiac index < 3, systemic vascular resistance index < 13).

RESULTS

In total, 79 patients (median age: 15.7 [range: 10.1-50.2] years) were included; of them, the primary endpoint occurred in 10 (13%; median follow-up: 1.9 [range: 0.1-18.8] years). Category C patients had significantly shorter freedom from the endpoint than categories A and B patients. Univariate analysis identified significant haemodynamic predictors, including Fontan pressure, pulmonary/systemic vascular resistance index, pulmonary/systemic flow, systemic arterial oxygen saturation, systemic venous oxygen saturation, systemic vascular resistance index, perfusion pressure, perfusion pressure < 53 mmHg, and category C. In multivariable analysis, perfusion pressure < 53 mmHg and category C emerged as predictors of heart transplantation/death alongside Fontan pressure.

CONCLUSION

Haemodynamic profiling of late post-Fontan patients using the cardiac index-systemic vascular resistance index plot can aid to comprehend the post-Fontan status and predict clinical prognosis.

Aerobic Capacity of Adults With Fontan Palliation: Disease-Specific Reference Values and Relationship to Outcomes

BACKGROUND

Patients with Fontan palliation have reduced aerobic capacity because of impaired cardiac, pulmonary, and skeletal muscle function. However, the assessment of aerobic capacity in this population still relies on comparisons with people without cardiovascular disease rather than comparison with the expected aerobic capacity of other Fontan patients. The purpose of this study was to determine the expected aerobic capacity of adults with Fontan palliation.

METHODS

Adults with Fontan palliation who underwent a cardiopulmonary exercise test at Mayo Clinic (2003-2023) were stratified into quartiles based on the predicted peak oxygen consumption (VO2). We assessed the correlates of predicted peak VO2 and the relationship between predicted peak VO2 quartiles and cardiovascular outcomes (death/transplant).

RESULTS

Of 323 patients (age, 29±9 years; 177 [55%] men), the median peak VO2 was 19.1 (15.2-23.9) mL/kg per minute, and this corresponds to a predicted peak VO2 of 51% (range, 19-88; interquartile range, 41-62). After multivariable adjustments, the correlates of predicted peak VO2 were body mass index (β±SE, -2.61±0.95; 2.61% decrease in predicted peak VO2 per 5 kg/m2 increase in body mass index; P=0.009), systemic saturation (β±SE, 3.65±0.85; 3.65% increase in predicted peak VO2 per 5% increase in oxygen saturation; P<0.001), and Fontan pressure (β±SE, -1.24±0.22; 1.24% decrease in predicted peak VO2 per 1 mm Hg increase in Fontan pressures; P<0.001). There was a 47% increase in the risk for death/transplant from a higher predicted peak VO2 quartile to the next lower quartile (adjusted hazard ratio, 1.47 [95% CI, 1.09-2.05]; P=0.01).

CONCLUSIONS

The results of the current study would help calibrate the interpretation of exercise test data in adults with Fontan palliation and improve risk stratification in this population. It also underscores the need to maintain normal Fontan hemodynamics and body weight, which are important determinants of aerobic capacity.

Effects of systemic ventricular assist in failing Fontan patients: a theoretical analysis using a computational model

Mechanical circulatory support is a potential treatment for failing Fontan patients. In this study, we performed a theoretical analysis using a computational model to clarify the effects of systemic ventricular assist device (VAD) in failing Fontan patients. Cardiac chambers and vascular systems were described using the time-varying elastance model and modified Windkessel model, respectively. A VAD was simulated as a nonlinear function. In systolic and diastolic ventricular dysfunction and atrioventricular valve regurgitation models, systemic VAD increased the cardiac index and decreased the central venous pressure (CVP). However, in the high pulmonary vascular resistance model, CVP became extremely high above 15 mmHg to maintain the cardiac index when the pulmonary vascular resistance index (PVRI) was above 5 Wood units m2. In Fontan patients with ventricular dysfunction or atrioventricular valve regurgitation, systemic VAD efficiently improves the hemodynamics. In Fontan patients with PVRI of > 5 Wood units m2, systemic VAD seems ineffective.

Haemodynamic contributors to pulmonary hypertension across the spectrum of adult congenital heart disease

AIMS

Adult congenital heart disease (ACHD) includes multiple disease states that predispose to pulmonary hypertension (PH). Haemodynamically, PH depends on abnormalities in three components: pulmonary blood flow (Qp), pulmonary vascular resistance (PVR) and pulmonary venous pressure (PVP). We sought to evaluate the prevalence and prognostic impact of individual haemodynamic abnormalities in ACHD.

METHODS AND RESULTS

Retrospective study of ACHD patients undergoing cardiac catheterization at Mayo Clinic between 1999 and 2022 who were followed for the combined endpoint of death/heart transplantation. Among 1005 patients, 37% had mean pulmonary artery pressure (mPAP) ≥25 mmHg with more systemic ventricular disease, cyanotic disease and shunt lesions, highest N-terminal pro-B-type natriuretic peptide and worse right heart remodelling/dysfunction. Among those with biventricular circulation, elevated PVP, PVR and mPAP were associated with prognosis, but not increased Qp >8 L/min. However, risk of death/transplant increased for PVR only at ≥3 Wood units (hazard ratio [HR] 3.00, 95% confidence interval [CI] 2.17-4.15; p < 0.0001) and for mPAP only at ≥25 mmHg (HR 3.15, 95% CI 2.17-4.58; p < 0.0001), not at current recommended lower cutpoints. Combined abnormalities in PVP and PVR were associated with worst outcome (HR 5.20, 95% CI 3.55-7.63; p < 0.0001) with intermediate risk with either abnormality (HR 2.11, 95% CI 1.46-3.04; p < 0.0001). Findings were consistent across type of biventricular ACHD. Only with the Fontan (univentricular) circulation was a lower mPAP threshold (20 mmHg) associated with adverse outcomes.

CONCLUSIONS

Elevation of mPAP ≥25 mmHg in ACHD with a biventricular circulation is prognostically important regardless of disease phenotype, but milder PH of 21-25 mmHg is not associated with adverse outcome unless associated with Fontan circulation. Elevation in PVP >15 mmHg and PVR ≥3 Wood units were each individually associated with mortality with combined abnormalities associated with greatest risk. Categorizing PH in ACHD by haemodynamic mechanism (PVR, PVP or Qp) allows meaningful prognostication, and may allow more unified study of targeted therapies across heterogeneous disease states in ACHD.

Comparison of Echocardiographically-Calculated Fontan Fenestration Gradient and Catheter-Based Measurement

BACKGROUND

Patients born with single ventricle anatomy typically undergo surgical palliation in three stages, culminating in the Fontan procedure. Assessment of flow across a Fontan fenestration by Doppler ultrasound theoretically allows for non-invasive estimation of the transpulmonary gradient (TPG). Our objective was to determine the relationship between Doppler-derived mean fenestration gradient (mFG) and direct catheter-based measurements of TPG in patients with fenestrated Fontans.

METHODS

We performed a single-center retrospective cohort study of 59 patients with fenestrated Fontans completed between 2000 and 2022. The primary outcome was catheter-based measurement of TPG and the primary predictor was mFG from echo performed within 6 months of the catheterization. Linear regression and R2 were used to determine the relationship between predictors and outcomes.

RESULTS

Catheter-based measurements of TPG and mFG were weakly correlated (R2 = 0.382, p < 0.001); the regression coefficient was 0.550, with a standard error of 0.09 for every increase in mFG (Cath TPG = 0.55 [mFG] + 1.92). mFG had a slightly better predictive relationship with cath-derived TPG in patients with systemic left ventricles with R2 of 0.47, p < 0.004.

CONCLUSION

mFG accounts for approximately 38% of the variance in catheter-derived TPG. Although mFG is non-invasive and intuitive, mFG in Fontan patients should be interpreted with caution and direct measurement by cardiac catheterization should be considered.

Perioperative considerations for non-cardiac procedures in patients with congenital heart disease: A practical overview

Providing thorough care for children with congenital heart disease (CHD) undergoing non-cardiac surgery requires a strong understanding of common heart defects and the procedures used to treat them. To care for these patients, multidisciplinary teams must consider the severity of the underlying cardiac disease, comorbid conditions, and preoperative severity of illness. The American Heart Association's Scientific Statement on Perioperative Considerations for Pediatric Patients with Congenital Heart Disease Presenting for Noncardiac Procedures offers valuable guidance.

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.

Augmented Biphasic Breathing Using Sniff and an Oral Positive Expiratory Pressure Device (Sniff-PEP) in Fontan Patients

The use of an oral positive expiratory pressure device (oPEP) with sniff breathing (Sniff-PEP) mimics biphasic ventilation. Biphasic ventilation increases pulmonary blood flow and cardiac output in Fontan patients. The aim of this study was to assess the effect of Sniff-PEP on Fontan flow velocities. A single-center, pilot, prospective study was carried out in 15 subjects with Fontan circulation enrolled to use the oPEP device for 1 month. Subjects were instructed on Sniff-PEP and to use the device for 10-15 min 3-4 times a day. Measurements of flow velocity and cardiac output were measured via echocardiogram and quality of life assessments were performed at baseline and 4-6 weeks later. The mean age at enrollment was 19.9 ± 8.7 years (age range of 10-37 years). 7 patients (47%) had dominant left ventricle and 8 (53%) had an open fenestration. There was a statistically significant increase in flow velocities in the hepatic vein from 27.5 ± 7.6 to 35.1 ± 11.3 cm/s (p = 0.003), left pulmonary artery from 51.6 ± 16.6 to 57.6 ± 21.1 cm/s (p = 0.01), and right pulmonary artery from 43.1 ± 14.2 to 45.8 ± 17.2 cm/s (p = 0.04). With chronic use, the mean fenestration gradient slightly decreased from 4.5 ± 1.6 to 4.1 ± 1.9 mmHg but the difference was not statistically significant (p = 0.14). oPEP device therapy increased flow velocity in several areas in the Fontan circulation with acute use. Further studies are needed to assess the effects long term.Clinical Trial Registration: URL: https://clinicaltrials.gov . Unique identifier: NCT03251742.

Machine Learning Analysis of Predictors for Inhaled Nitric Oxide Therapy Administration Time Post Congenital Heart Disease Surgery: A Single-Center Observational Study

Background Congenital heart disease (CHD) is a structural deformity of the heart present at birth. Pulmonary hypertension (PH) may arise from increased blood flow to the lungs, persistent pulmonary arterial pressure elevation, or the use of cardiopulmonary bypass (CPB) during surgical repair. Inhaled nitric oxide (iNO) selectively reduces high blood pressure in the pulmonary vessels without lowering systemic blood pressure, making it useful for treating children with postoperative PH due to heart disease. However, reducing or stopping iNO can exacerbate postoperative PH and hypoxemia, necessitating long-term administration and careful tapering. This study aimed to evaluate, using machine learning (ML), factors that predict the need for long-term iNO administration after open heart surgery in CHD patients in the postoperative ICU, primarily for PH management. Methods We used an ML approach to establish an algorithm to predict 'patients with long-term use of iNO' and validate its accuracy in 34 pediatric postoperative open heart surgery patients who survived and were discharged from the ICU at Kagoshima University Hospital between April 2016 and March 2019. All patients were started on iNO therapy upon ICU admission. Overall, 16 features reflecting patient and surgical characteristics were utilized to predict the patients who needed iNO for over 168 hours using ML analysis with AutoGluon. The dataset was randomly classified into training and test cohorts, comprising 80% and 20% of the data, respectively. In the training cohort, the ML model was constructed using the important features selected by the decrease in Gini impurity and a synthetic oversampling technique. In the testing cohort, the prediction performance of the ML model was evaluated by calculating the area under the receiver operating characteristics curve (AUC) and accuracy. Results Among 28 patients in the training cohort, five needed iNO for over 168 hours; among six patients in the testing cohort, one needed iNO for over 168 hours. CPB, aortic clamp time, in-out balance, and lactate were the four most important features for predicting the need for iNO for over 168 hours. In the training cohorts, the ML model achieved perfect classification with an AUC of 1.00. In the testing cohort, the ML model also achieved perfect classification with an AUC of 1.00 and an accuracy of 1.00. Conclusion The ML approach identified that four factors (CPB, in-out balance, aortic cross-clamp time, and lactate) are strongly associated with the need for long-term iNO administration after open heart surgery in CHD patients. By understanding the outcomes of this study, we can more effectively manage iNO administration in postoperative open heart surgery in CHD patients with PH, potentially preventing the recurrence of postoperative PH and hypoxemia, thereby contributing to safer patient management.

Association of patient-level characteristics with long-term outcomes after Fontan palliation: Rationale, design, and baseline characteristics of the Pediatric Cardiac Care Consortium Fontan cohort study

BACKGROUND

The Fontan operation is used to palliate single ventricle congenital heart defects (CHD) but poses significant morbidity and mortality risks. We present the design, planned analyses, and rationale for a long-term Fontan cohort study aiming to examine the association of patient characteristics at the time of Fontan with post-Fontan morbidity and mortality.

METHODS AND RESULTS

We used the Pediatric Cardiac Care Consortium (PCCC), a US-based, multicenter registry of pediatric cardiac surgeries to identify patients who underwent the Fontan procedure for single ventricle CHD between 1 and 21 years of age. The primary outcomes are in-hospital Fontan failure (death or takedown) and post-discharge mortality through 2022. A total of 1461 (males 62.1%) patients met eligibility criteria and were included in the analytical cohort. The median age at Fontan evaluation was 3.1 years (IQR: 2.4-4.3). While 95 patients experienced in-hospital Fontan failure (78 deaths and 17 Fontan takedown), 1366 (93.5%) survived to discharge with Fontan physiology and formed the long-term analysis cohort. Over a median follow-up of 21.2 years (IQR: 18.4-24.5) 184 post-discharge deaths occurred. Thirty-year post Fontan survival was 75.0% (95% CI: 72.3%-77.8%) for all Fontan types with higher rates for current techniques such as lateral tunnel and extracardiac conduit 77.1% (95% CI: 73.5-80.8).

CONCLUSION

The PCCC Fontan study aims to identify predictors for post-Fontan morbidity and mortality, enabling risk- stratification and informing surveillance practices. Additionally, the study may guide therapeutic interventions aiming to optimize hemodynamics and enhance Fontan longevity for individual patients.

Outcomes of Esophageal Varices in Adults With Fontan Palliation and Liver Cirrhosis

Background

The purpose of this study was to define the risk and outcomes of esophageal varices in adults with Fontan palliation and liver cirrhosis undergoing esophagogastroduodenoscopy (EGD).

Method

The results of EGD, abdominal ultrasound, and liver biopsy, as well as clinic notes from the hepatologist, were reviewed to determine the diagnosis of cirrhosis and esophageal varices. The incidence of acute gastrointestinal bleeding complication was assessed among patients with esophageal varices using the time of EGD as the baseline.

Results

Of 149 patients with Fontan palliation and liver cirrhosis, the prevalence of esophageal varices at baseline EGD was 34% (51 of 149). Of 98 patients without esophageal varices at baseline EGD, 27 (27%) underwent subsequent EGD, of whom 11 showed a new diagnosis of esophageal varices. The incidence of a new diagnosis of esophageal varices was 9% per year. Of 62 patients with esophageal varices, 9 (15%) had acute gastrointestinal bleeding complications during 45 (37-62) months of follow-up, yielding an incidence of 5% per year. Of the 9 patients, 8 underwent EGD and variceal banding during the hospitalization for bleeding and 1 patient died of septicaemia. Of the 8 patients who survived to hospital discharge, 2 patients were readmitted for esophageal bleeding within 12 months from the index hospitalization. Higher hepatic vein wedge pressure and hepatic vein pressure gradient were associated with esophageal varices and bleeding complications.

Conclusions

In this selected sample of adults with Fontan palliation and liver cirrhosis, esophageal varices were relatively common, and patients with esophageal varices had risk of bleeding complications.

Outcomes after initial heart failure consultation in Fontan patients

BACKGROUND

Patients with Fontan failure are high-risk candidates for heart transplantation and other advanced therapies. Understanding the outcomes following initial heart failure consultation can help define appropriate timing of referral for advanced heart failure care.

METHODS

This is a survey study of heart failure providers seeing any Fontan patient for initial heart failure care. Part 1 of the survey captured data on clinical characteristics at the time of heart failure consultation, and Part 2, completed 30 days later, captured outcomes (death, transplant evaluation outcome, and other interventions). Patients were classified as "too late" (death or declined for transplant due to being too sick) and/or "care escalation" (ventricular assist device implanted, inotrope initiated, and/or listed for transplant), within 30 days. "Late referral" was defined as those referred too late and/or had care escalation.

RESULTS

Between 7/2020 and 7/2022, 77 Fontan patients (52% inpatient) had an initial heart failure consultation. Ten per cent were referred too late (6 were too sick for heart transplantation with one subsequent death, and two others died without heart transplantation evaluation, within 30 days), and 36% had care escalation (21 listed ± 5 ventricular assist device implanted ± 6 inotrope initiated). Overall, 42% were late referrals. Heart failure consultation < 1 year after Fontan surgery was strongly associated with late referral (OR 6.2, 95% CI 1.8-21.5, p=0.004).

CONCLUSIONS

Over 40% of Fontan patients seen for an initial heart failure consultation were late referrals, with 10% dying or being declined for transplant within a month of consultation. Earlier referral, particularly for those with heart failure soon after Fontan surgery, should be encouraged.

Heart Failure Staging and Indications for Advanced Therapies in Adults with Congenital Heart Disease

Heart failure (HF) is common in adults with congenital heart disease (CHD), and it is the leading cause of death in this population. Adults with CHD presenting with stage D HF have a poor prognosis, and early recognition of signs of advanced HF and referral for advanced therapies for HF offer the best survival as compared with other therapies. The indications for advanced therapies for HF outlined in this article should serve as a guide for clinicians to determine the optimal time for referral. Palliative care should be part of the multidisciplinary care model for HF in patients with CHD.

Evaluation of the total hydrodynamic energy loss using 4D flow MRI in a case with Fontan failure

Fontan Failure (FF) is a common problem for single-ventricle patients as they reach adulthood. Although several mechanisms may cause FF, an optimized blood flow stream through the surgical conduits is essential to avoid excessive energy loss (EL). Recent clinical studies showed EL is related to the quality of life, exercise capacity, and hepatic function since the single-ventricle feeds pulmonary and systemic circulation serially. 4D flow MRI effectively estimates EL in Fontan circulation and allows clinicians to compare the effectiveness of the treatment strategy concerning pre-intervention. Here, we present 26-year-old women with FF who had normal cardiac catheterization findings and were treated according to high EL definitions that are measured through 4D flow MRI.

In vitro hemodynamic performance of a blood pump for self-powered venous assist in univentricular hearts

Univentricular heart anomalies represent a group of severe congenital heart defects necessitating early surgical intervention in infancy. The Fontan procedure, the final stage of single-ventricle palliation, establishes a serial connection between systemic and pulmonary circulation by channeling venous return to the lungs. The absence of the subpulmonary ventricle in this peculiar circulation progressively eventuates in failure, primarily due to chronic elevation in inferior vena cava (IVC) pressure. This study experimentally validates the effectiveness of an intracorporeally-powered venous ejector pump (VEP) in reducing IVC pressure in Fontan patients. The VEP exploits a fraction of aortic flow to create a jet-venturi effect for the IVC, negating the external power requirement and driveline infections. An invitro Fontan mock-up circulation loop is developed and the impact of VEP design parameters and physiological conditions is assessed using both idealized and patient-specific total cavopulmonary connection (TCPC) phantoms. The VEP performance in reducing IVC pressure exhibited an inverse relationship with the cardiac output and extra-cardiac conduit (ECC) size and a proportional relationship with the transpulmonary pressure gradient (TPG) and mean arterial pressure (MAP). The ideal VEP with fail-safe features provided an IVC pressure drop of 1.82 ± 0.49, 2.45 ± 0.54, and 3.12 ± 0.43 mm Hg for TPG values of 6, 8, and 10 mm Hg, respectively, averaged over all ECC sizes and cardiac outputs. Furthermore, the arterial oxygen saturation was consistently maintained above 85% during full-assist mode. These results emphasize the potential utility of the VEP to mitigate elevated venous pressure in Fontan patients.

Utility of Balloon Occlusion Testing in Determining Fontan Suitability Among Patients with Elevated Pulmonary Artery Pressure and Additional Antegrade Pulmonary Blood Flow

In individuals with a single ventricle undergoing evaluation before Fontan surgery, the presence of excessive pulmonary blood flow can contribute to increased pulmonary artery pressure, notably in those who had a Glenn procedure with antegrade pulmonary flow. 28 patients who had previously undergone Glenn anastomosis with antegrade pulmonary blood flow (APBF) and with elevated mean pulmonary artery (mPAP) pressure > 15 mmHg in diagnostic catheter angiography were included in the study. After addressing other anatomical factors that could affect pulmonary artery pressure, APBF was occluded with semi-compliant, Wedge or sizing balloons to measure pulmonary artery pressure accurately. 23 patients (82% of the cohort) advanced to Fontan completion. In this group, median mPAP dropped from 20.5 (IQR 19-22) mmHg to 13 (IQR 12-14) mmHg post-test (p < 0.001). Median PVR post-test was 1.8 (IQR 1.5-2.1) WU m2. SpO2 levels decreased from a median of 88% (IQR 86%-93%) pre-test to 80% (IQR 75%-84%) post-test (p < 0.001). In five patients, elevated mPAP post-test occlusion on diagnostic catheter angiography led to non-completion of Fontan circulation. In this group, median pre- and post-test mPAP were 23 mmHg (IQR 21.5-23.5) and 19 mmHg (IQR 18.5-20), respectively (p = 0.038). Median post-test PVR was 3.8 (IQR 3.6-4.5) WU m2. SpO2 levels decreased from a median of 79% (IQR 76%-81%) pre-test to 77% (IQR 73.5%-80%) post-test (p = 0.039). Our study presents a specialized approach for patients initially deemed unsuitable for Fontan due to elevated pulmonary artery pressures. We were able to successfully complete the Fontan procedure in the majority of these high-risk cases after temporary balloon occlusion test.

The Effect of Udenafil on Heart Rate and Blood Pressure in Adolescents With the Fontan Circulation

The Fontan Udenafil Exercise Longitudinal (FUEL) trial showed that treatment with udenafil was associated with improved exercise performance at the ventilatory anaerobic threshold in children with Fontan physiology. However, it is not known how the initiation of phosphodiesterase 5 inhibitor therapy affects heart rate and blood pressure in this population. These data may help inform patient selection and monitoring after the initiation of udenafil therapy. The purpose of this study is to evaluate the effects of udenafil on vital signs in the cohort of patients enrolled in the FUEL trial. This international, multicenter, randomized, double-blind, placebo-controlled trial of udenafil included adolescents with single ventricle congenital heart disease who had undergone Fontan palliation. Changes in vital signs (heart rate [HR], systolic [SBP] and diastolic blood pressure [DBP]) were compared both to subject baseline and between the treatment and the placebo groups. Additional exploratory analyses were performed to evaluate changes in vital signs for prespecified subpopulations believed to be most sensitive to udenafil initiation. Baseline characteristics were similar between the treatment and placebo cohorts (n = 200 for each). The groups demonstrated a decrease in HR, SBP, and DBP 2 hours after drug/placebo administration, except SBP in the placebo group. There was an increase in SBP from baseline to after 6-min walk test in the treatment and placebo groups, and the treatment group showed an increase in HR (87.4 ± 15.0 to 93.1 ± 19.4 beats/min, p <0.01) after exercise. When comparing changes from baseline to the 26-week study visit, small decreases in both SBP (-1.9 ± 12.3 mm Hg, p = 0.03) and DBP (-3.0 ± 9.6 mm Hg, p <0.01) were seen in the treatment group. There were no clinically significant differences between treatment and placebo group in change in HR or blood pressure in the youngest age quartile, lightest weight quartile, or those on afterload-reducing agents. In conclusion, initiation of treatment with udenafil in patients with Fontan circulation was not associated with clinically significant changes in vital signs, implying that for patients similar to those enrolled in the FUEL trial, udenafil can be started without the requirement for additional monitoring after initial administration.

Switching the Left and the Right Hearts: A Novel Bi-ventricle Mechanical Support Strategy with Spared Native Single-Ventricle

End-stage Fontan patients with single-ventricle (SV) circulation are often bridged-to-heart transplantation via mechanical circulatory support (MCS). Donor shortage and complexity of the SV physiology demand innovative MCS. In this paper, an out-of-the-box circulation concept, in which the left and right ventricles are switched with each other is introduced as a novel bi-ventricle MCS configuration for the "failing" Fontan patients. In the proposed configuration, the systemic circulation is maintained through a conventional mechanical ventricle assist device (VAD) while the venous circulation is delegated to the native SV. This approach spares the SV and puts it to a new use at the right-side providing the most-needed venous flow pulsatility to the failed Fontan circulation. To analyze its feasibility and performance, eight SV failure modes have been studied via an established multi-compartmental lumped parameter cardiovascular model (LPM). Here the LPM model is experimentally validated against the corresponding pulsatile mock-up flow loop measurements of a representative 15-year-old Fontan patient employing a clinically-approved VAD (Medtronic-HeartWare). The proposed surgical configuration maintained the healthy cardiac index (3-3.5 l/min/m2) and the normal mean systemic arterial pressure levels. For a failed SV with low ejection fraction (EF = 26%), representing a typical systemic Fontan failure, the proposed configuration enabled a ~ 28 mmHg amplitude in the venous/pulmonary waveforms and a 2 mmHg decrease in the central venous pressure (CVP) together with acceptable mean pulmonary artery pressures (17.5 mmHg). The pulmonary vascular resistance (PVR)-SV failure case provided a ~ 5 mmHg drop in the CVP, with venous/pulmonary pulsatility reaching to ~ 22 mmHg. For the high PVR failure case with a healthy SV (EF = 44%) pulmonary hypertension is likely to occur as expected. While this condition is routinely encountered during the heart transplantation and managed through pulmonary vasodilators a need for precise functional assessment of the spared failed-ventricle is recommended if utilized in the PVR failure mode. Comprehensive in vitro and in silico results encourage this novel concept as a low-cost, more physiological alternative to the conventional bi-ventricle MCS pending animal experiments.

Thyroid dysfunction in pediatric Fontan patients is associated with unfavorable hemodynamic status and severity of protein-losing enteropathy: A report from the Fontan care network

Background

Thyroid dysfunction may have adverse effects on Fontan hemodynamics. Data on thyroid function in pediatric Fontan patients with or without protein-losing enteropathy (PLE) are limited.

Methods

This retrospective multicenter study included 67 Fontan patients (median age 10.9 years; 35.8% female; 28.4% PLE) in whom thyroid function testing was performed.

Results

Subclinical hypothyroidism (SHT) was present in 16 (23.9%) patients. Subjects with SHT had significantly lower systolic blood pressure (p = 0.014) and body weight z-score (p = 0.006), were in a worse New York Heart Association (NYHA) functional class (p = 0.004), were more often pacing dependent (p = 0.007), and were more likely to have PLE (p = 0.033, 8/19 (42.1%) patients). Serum thyroid stimulating hormone (TSH) levels were significantly higher in patients with NYHA class ≥ II (p = 0.005), significant atrioventricular valve regurgitation (p = 0.023), elevated serum natriuretic peptides (p = 0.031), and in those with PLE (p = 0.002). Patients with active PLE had significantly higher TSH levels than those in remission (p = 0.003). A strong inverse relationship was found between lower free triiodothyronine (fT3) levels and natriuretic peptides (r: -0.599, p = 0.040). Using binary logistic regression analysis we found that worse NYHA class was an independent predictor of SHT (OR 4.2; 95% CI 1.1-16.1, p = 0.036).

Conclusions

Subclinical thyroid dysfunction is common in Fontan, particularly in patients with hemodynamic derangements and PLE. Future studies are needed to address the prognostic implications of thyroid dysfunction in the Fontan population.

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.

Exercise-induced changes in pulmonary artery wedge pressure in adults post-Fontan versus heart failure with preserved ejection fraction and non-cardiac dyspnoea

AIMS

Despite their universal predisposition, diagnosing diastolic dysfunction in patients post-Fontan palliation is challenging. Our aim was to compare exercise haemodynamics between adults post-Fontan and patients with heart failure with preserved ejection fraction (HFpEF) and non-cardiac dyspnoea (NCD).

METHODS AND RESULTS

Twenty-four adults (age ≥18 years) post-Fontan palliation with resting and exercise pulmonary artery wedge pressure (PAWP) measured during supine biking were identified. Forty-eight patients with HFpEF and 48 with NCD diagnosed at catheterization were selected for comparison. Mean age for Fontan patients was 30.3 ± 7.5 years; median ventricular ejection fraction was 52.5% (45-55.8), being <50% in 37.5%. Resting PAWP among Fontan patients was 10.2 ± 3.5 mmHg (>12 mmHg in 25%); PAWP was lower in Fontan patients than in HFpEF but higher than NCD. During exercise, PAWP was lower in the Fontan group than HFpEF (22.5 mmHg [19.3-28] vs. 28.2 ± 6.3; p = 0.0006) but higher than NCD (11.2 ± 4.2, p ≤ 0.0001). However, there were no differences in ΔPAWP/ΔQs between Fontan and HFpEF patients (4.0 [2.1-7.3] vs. 2.7 [1.6-4.4]; p = 0.10) with the ratio being higher post-Fontan than in NCD (0.6 [0.2-1.2]; p < 0.0001). ΔPAWP/ΔQs remained similar between HFpEF and Fontan patients even when those with ejection fraction <50% were excluded (2.7 [1.6-4.4] vs. 2.7 [1.0-5.8]; p = 0.97).

CONCLUSION

There were no differences in ΔPAWP/ΔQs ratios between post-Fontan and HFpEF patients, supporting markedly abnormal single ventricle compliance despite lower resting and exercise PAWP. Therefore, exercise invasive haemodynamics may represent a novel tool for the diagnosis of diastolic dysfunction in Fontan patients.

Impact of Udenafil on Echocardiographic Indices of Single Ventricle Size and Function in FUEL Study Participants

BACKGROUND

The FUEL trial (Fontan Udenafil Exercise Longitudinal) demonstrated statistical improvements in exercise capacity following 6 months of treatment with udenafil (87.5 mg po BID). The effect of udenafil on echocardiographic measures of single ventricle function in this cohort has not been studied.

METHODS

The 400 enrolled participants were randomized 1:1 to udenafil or placebo. Protocol echocardiograms were obtained at baseline and 26 weeks after initiation of udenafil/placebo. Linear regression compared change from baseline indices of single ventricle systolic, diastolic and global function, atrioventricular valve regurgitation, and mean Fontan fenestration gradient in the udenafil cohort versus placebo, controlling for ventricular morphology (left ventricle versus right ventricle/other) and baseline value.

RESULTS

The udenafil participants (n=191) had significantly improved between baseline and 26 weeks visits compared to placebo participants (n=195) in myocardial performance index (P=0.03, adjusted mean difference [SE] of changes between groups -0.03[0.01]), atrioventricular valve inflow peak E (P=0.009, 3.95 [1.50]), and A velocities (P=0.034, 3.46 [1.62]), and annular Doppler tissue imaging-derived peak e' velocity (P=0.008, 0.60[0.23]). There were no significant differences in change in single ventricle size, systolic function, atrioventricular valve regurgitation severity, or mean fenestration gradient. Participants with a dominant left ventricle had significantly more favorable baseline values of indices of single ventricle size and function (lower volumes and areas, E/e' ratio, systolic:diastolic time and atrioventricular valve regurgitation, and higher annular s' and e' velocity).

CONCLUSIONS

FUEL participants who received udenafil demonstrated a statistically significant improvement in some global and diastolic echo indices. Although small, the changes in diastolic function suggest improvement in pulmonary venous return and/or augmented ventricular compliance, which may help explain improved exercise performance in that cohort.

REGISTRATION

URL: https://clinicaltrials.gov; Unique Identifier: NCT02741115.

Induction of aggressive arterial and venous dilation therapy in addition to pulmonary dilation therapy (super-Fontan strategy) improves Fontan circulation both at rest and during treadmill exercise

Objective

Methods

Results

Conclusions

Preoperative N-terminal pro-brain natriuretic peptide is associated with Fontan outcomes

OBJECTIVE

The role of preoperative N-terminal pro-brain natriuretic peptide level in patient outcomes after the Fontan operation remains unclear.

METHODS

The medical records of all patients who underwent their first Fontan operation from June 2011 to October 2019 in our tertiary referral pediatric cardiac center were retrospectively reviewed. Preoperative hemodynamic factors and N-terminal pro-brain natriuretic peptide were analyzed to test the association of mortality and morbidity.

RESULTS

We enrolled 110 patients (men/women 62/48; median age, 4.1 [3.4, 5.8] years; median follow-up period, 4.28 [2.31, 6.71] years). Almost all operations were extracardiac conduits (98.2%). Primary outcomes of death, Fontan takedown, and heart transplantation were observed in 9 patients (8.2%). Abnormal ventricular contractility, elevated preoperative pulmonary artery pressure, high pulmonary vascular resistance index, and high log₁₀ N-terminal pro-brain natriuretic peptide level were associated with poor outcomes.

SECONDARY OUTCOMES

atrioventricular valve regurgitation moderate or greater, elevated pulmonary artery pressure, high pulmonary vascular resistance index, and high log₁₀ N-terminal pro-brain natriuretic peptide level were associated with rehospitalization due to heart failure. Multivariable Cox regression analysis revealed that log₁₀ N-terminal pro-brain natriuretic peptide was the only significant predictor of all primary and secondary outcomes. A scoring system including factors of pulmonary artery pressure, pulmonary vascular resistance index, and N-terminal pro-brain natriuretic peptide was established, and the risk stratification is associated with outcomes after the Fontan operation.

CONCLUSIONS

High preoperative N-terminal pro-brain natriuretic peptide was associated with poor outcomes after the Fontan operation.

Predictive factors contributing to prolonged recovery in patients after Fontan operation

Background

Prolonged recovery is a severe issue in patients after Fontan operation. However, predictive factors related to this issue are not adequately evaluated. The present study aimed to investigate potential predictive factors which can predict Fontan postoperative recovery.

Methods

We retrospectively reviewed the perioperative medical records of patients with Fontan surgery between January 2015 and December 2018, and divided patients with > 75%ile cardiac intensive care unit stay into prolonged recovery group. The others were assigned to standard recovery group. Patients that died or underwent a Fontan takedown were excluded. Statistical analysis was performed to compare data difference of the two groups.

Results

282/307 cases fulfilled the inclusion criteria. Seventy patients were considered in prolonged recovery and 212 patients were defined as standard recovery. Pre- and intra-operative data showed a higher incidence of heterotaxy syndrome, longer cardiopulmonary bypass and aortic cross-clamp time in the prolonged recovery group. Postoperative information analysis displayed that ventilation time, oxygen index after extubation, hemodynamic data, inotropic score (IS), drainage volume, volume resuscitation, pulmonary hypertension (PH) treatment, and surgical reintervention were significantly different between the two groups. Higher IS postoperatively, and PH treatment and higher fluid resuscitation within two days were independent predictive factors for prolonged recovery in our multivariate model. C-statistic model showed a high predictive ability in prolonged recovery by using the three factors.

Conclusions

Ventilation time, higher IS in postoperative day, and PH treatment and higher fluid resuscitation within two days were independent risk factors and have a high predictability for Fontan prolonged recovery.

Optimal Fenestration of the Fontan Circulation

In this paper, we develop a pulsatile compartmental model of the Fontan circulation and use it to explore the effects of a fenestration added to this physiology. A fenestration is a shunt between the systemic and pulmonary veins that is added either at the time of Fontan conversion or at a later time for the treatment of complications. This shunt increases cardiac output and decreases systemic venous pressure. However, these hemodynamic benefits are achieved at the expense of a decrease in the arterial oxygen saturation. The model developed in this paper incorporates fenestration size as a parameter and describes both blood flow and oxygen transport. It is calibrated to clinical data from Fontan patients, and we use it to study the impact of a fenestration on several hemodynamic variables, including systemic oxygen availability, effective oxygen availability, and systemic venous pressure. In certain scenarios corresponding to high-risk Fontan physiology, we demonstrate the existence of a range of fenestration sizes in which the systemic oxygen availability remains relatively constant while the systemic venous pressure decreases.

Catheterization in Adults With Congenital Heart Disease: A Primer for the Noncongenital Proceduralist

Currently in the United States, more than 1 million adults have congenital heart disease. Therefore, it will be inevitable for providers performing cardiac catheterization to be faced with adults with repaired congenital heart abnormalities. Moreover, a meticulous approach to every cardiac catheterization procedure is mandatory to avoid missing unrecognized congenital lesions presenting in adulthood. The authors provide a primer for cardiac catheterization procedures in adults with congenital heart disease, reviewing key procedural components: flow calculation, detection of shunts according to different lesions, and, when indicated, ventricular angiography and coronary angiography.

Hepatic and Renal Consequences of Single Ventricle Physiology Palliated with the Fontan Operation

Over time the long-term survival has dramatically increased for patients with complex congenital heart disease who undergo the Fontan operation. With this increased survival, it has become apparent that such a circulation has important consequences for other organ systems, particularly the liver and kidney. The adverse milieu created by chronic venous hypertension, low cardiac output and an inflammatory state contribute to the pathologic changes observed in the liver and kidneys over the long-term in Fontan patients. The clinical importance of these hepatic and renal comorbidities have only recently begun to be recognized in the context of increasing life expectancy in this population. The objectives of this review are: i) to provide an overview of the pathophysiology of the Fontan circulation and how liver and kidney disease evolve in this setting; ii) to summarize the current evidence base as it relates to the diagnostic approach to liver and kidney disease in Fontan patients; and, iii) to discuss the therapeutic approaches to Fontan associated liver and kidney disease. Given that this is a very active area of research in congenital heart disease, we have identified knowledge gaps and priority research areas to improve the care of Fontan patients. These include: i) establishing the optimal diagnostic tests to detect and track liver and kidney disease change over time,; ii) determining what treatable risk factors contribute to the development of liver and kidney disease; and, iii) evaluating therapies to prevent or slow progression of liver and kidney disease.

Late Fontan Circulatory Failure. What Drives Systemic Venous Congestion and Low Cardiac Output in Adult Fontan Patients?

The Fontan circulation provides definite palliation for children born with a single anatomical or functional ventricle by diverting systemic venous blood directly to the pulmonary arteries, effectively rendering systemic venous return into portal vessels to the lung. Although this restores pulmonary blood flow and avoids the mixture of oxygenated and deoxygenated blood, it also results in elevated systemic venous pressures and low cardiac output. These are the two hallmarks of any Fontan circulation and the cause of Fontan circulatory failure later in life. We highlight the determinants of systemic venous return, its changed relationship with the pulmonary circulation, how it affects preload, and the changed role of the heart (myocardium, valves, and heart rate). By critically evaluating the components of the Fontan circulation, we hope to give some clues in how to optimize the Fontan circulation and avenues for future research.

Invasive Hemodynamic Evaluation of the Fontan Circulation: Current Day Practice and Limitations

PURPOSE OF REVIEW

Establishing the Fontan circulation has led to improved survival in patients born with complex congenital heart diseases. Despite early success, the long-term course of Fontan patients is complicated by multi-organ dysfunction, mainly due to a combination of low resting and blunted exercise-augmented cardiac output as well as elevated central venous (Fontan) pressure. Similarly, despite absolute hemodynamic differences compared to the normal population with biventricular circulation, the "normal" ranges of hemodynamic parameters specific to age-appropriate Fontan circulation have not been well defined. With the ever-increasing population of patients requiring Fontan correction, it is of utmost importance that an acceptable range of hemodynamics in this highly complex patient cohort is better defined.

RECENT FINDINGS

Multiple publications have described hemodynamic limitations and potential management options in patients with Fontan circulation; however, an acceptable range of hemodynamic parameters in this patient population has not been well defined. Identification of "normal" hemodynamic parameters among patients with Fontan circulation will allow physicians to more objectively define indications for intervention, which is a necessary first step to eliminate institutional and regional heterogeneity in Fontan management and potentially improve long-term clinical outcomes.

Heart transplant indications, considerations and outcomes in Fontan patients: Age-related nuances, transplant listing and disease-specific indications

In the current era, 5-10% of Fontan patients die or need a transplant in childhood, and approximately 50% will experience the same fate by age 40 years. Heart transplant (HTx) can be successful for selected children and adults with Fontan circulatory failure (FCF) of any mechanism, with a 1-year post-transplant survival approaching 90% in children and 80% in the largest single-centre adult Fontan HTx experience. Protein losing enteropathy and plastic bronchitis can be expected to resolve post-transplant and limited data suggests patients with FALD who survive HTx can expect improvement in liver health. Early Fontan failure, within 12 months of Fontan completion, is not easily rescued by HTx and late referrals / failure to refer adult patients remains problematic. Very little is known about the numbers of patients not referred, turned down following assessment for HTx, or dying on the waiting list which are needed to understand the complete picture of HTx in the Fontan population and to identify where best to focus quality improvement efforts. Recent revisions to listing prioritization in Canada with considerations specific to the Fontan population aim to mitigate the fact that the status listing criteria are not tailored to the congenital heart population. Transplanting high-risk children prior to Fontan completion, developing ACHD transplant centres of expertise which can also offer combined heart-liver transplant when appropriate, and improving single ventricle mechanical support options and criteria for both adults and children may help mitigate the early post-listing mortality.

Pulsatility Index in Different Modifications of Fontan Palliation: An Echocardiographic Assessment

BACKGROUND

Adding pulsation to the Fontan circulation might change the fate of patients palliated by this procedure. Our aim was to compare the pulsatility index (PI) of the pulmonary artery (PA) between the various modifications of Fontan palliation.

METHODS

Doppler-derived PI was measured in PA branches of a cohort of 28 patients palliated by 6 modifications of Fontan procedure. A group of normal individuals was included for comparison.

RESULTS

Atriopulmonary connection (APC) group had the highest PA branches PI and statistically was close to the PI of the normal individuals (right pulmonary artery [RPA] PI of 1.58 vs. 1.63; p = 0.99 and left pulmonary artery [LPA] PI of 1.54 vs. 1.68; p = 0.46, respectively). The lowest PA branches PI was seen in the group of extracardiac total cavopulmonary connection (RPA PI of 0.62 and LPA PI of 0.65). Other 4 modifications including the extracardiac conduit with oversewn pulmonary valve, extracardiac conduit with preserved adjusted antegrade flow, extracardiac conduit from inferior vena cava onto the rudimentary right ventricle and lateral tunnel had a mean “RPA and LPA” PI of “1.19 and 1.17”, “1.16 and 1.11”, “1.13 and 1.11”, “0.82 and 0.84”, respectively. The modified Dunnett's post hoc test has shown a significant statistical decline in PI of all modifications compared to the normal individuals except for the APC group.

CONCLUSIONS

Fontan palliated patients in different groups of surgical modification showed a spectrum of Doppler-derived PI with the highest amounts belong to the groups of pulsatile Fontan.

Cardiac Imaging in Patients After Fontan Palliation: Which Test and When?

The Fontan operation represents the final stage of a series of palliative surgical procedures for children born with complex congenital heart disease, where a "usual" biventricular physiology cannot be restored. The palliation results in the direct connection of the systemic venous returns to the pulmonary arterial circulation without an interposed ventricle. In this unique physiology, systemic venous hypertension and intrathoracic pressures changes due to respiratory mechanics play the main role for propelling blood through the pulmonary vasculature. Although the Fontan operation has dramatically improved survival in patients with a single ventricle congenital heart disease, significant morbidity is still a concern. Patients with Fontan physiology are in fact suffering from a multitude of complications mainly due to the increased systemic venous pressure. Consequently, these patients need close clinical and imaging monitoring, where cardiac exams play a key role. In this article, we review the main cardiac imaging modalities available, summarizing their main strengths and limitations in this peculiar setting. The main purpose is to provide a practical approach for all clinicians involved in the care of these patients, even for those less experienced in cardiac imaging.

Circulatory Response to Rapid Volume Expansion and Cardiorespiratory Fitness in Fontan Circulation

The role of dysfunction of the single ventricle in Fontan failure is incompletely understood. We aimed to evaluate hemodynamic responses to preload increase in Fontan circulation, to determine whether circulatory limitations in different locations identified by experimental preload increase are associated with cardiorespiratory fitness (CRF), and to assess the impact of left versus right ventricular morphology. In 38 consecutive patients (median age = 16.6 years, 16 females), heart catheterization was supplemented with a rapid 5-mL/kg body weight volume expansion. Central venous pressure (CVP), ventricular end-diastolic pressure (VEDP), and peak systolic pressure were averaged for 15‒30 s, 45‒120 s, and 4‒6 min (steady state), respectively. CRF was assessed by peak oxygen consumption (VO_2peak) and ventilatory threshold (VT). Median CVP increased from 13 mmHg at baseline to 14.5 mmHg (p < 0.001) at steady state. CVP increased by more than 20% in eight patients. Median VEDP increased from 10 mmHg at baseline to 11.5 mmHg (p < 0.001). Ten patients had elevated VEDP at steady state, and in 21, VEDP increased more than 20%. The transpulmonary pressure difference (CVP‒VEDP) and CVP were consistently higher in patients with right ventricular morphology across repeated measurements. CVP at any stage was associated with VO_2peak and VT. VEDP after volume expansion was associated with VT. Preload challenge demonstrates the limitations beyond baseline measurements. Elevation of both CVP and VEDP are associated with impaired CRF. Transpulmonary flow limitation was more pronounced in right ventricular morphology. Ventricular dysfunction may contribute to functional impairment after Fontan operation in young adulthood.ClinicalTrials.gov identifier NCT02378857.

Use of Pulmonary Arterial Hypertension Therapies in Patients with a Fontan Circulation: Current Practice Across the United Kingdom

Background

The Fontan circulation is a successful operative strategy for abolishing cyanosis and chronic volume overload in patients with congenital heart disease with single ventricle physiology. “Fontan failure” is a major cause of poor quality of life and mortality in these patients. We assessed the number and clinical characteristics of adult patients with Fontan physiology receiving pulmonary arterial hypertension (PAH) therapies across specialist centers in the United Kingdom.

Methods and Results

We identified all adult patients with a Fontan‐type circulation under active follow‐up in 10 specialist congenital heart disease centers in England and Scotland between 2009 and 2019. Patients taking PAH therapies were matched to untreated patients. A survey of experts was also performed. Of 1538 patients with Fontan followed in specialist centers, only 76 (4.9%) received PAH therapies during follow‐up. The vast majority (90.8%) were treated with a phosphodiesterase‐5 inhibitor. In 33% of patients, PAH therapies were started after surgery or during hospital admission. In the matched cohort, treated patients were more likely to be significantly limited, have ascites, have a history of protein‐losing enteropathy, or receive loop diuretics (P<0.0001 for all), also reflecting survey responses indicating that failing Fontan is an important treatment target. After a median of 12 months (11–15 months), functional class was more likely to improve in the treated group (P=0.01), with no other changes in clinical parameters or safety issues.

Conclusions

PAH therapies are used in adult patients with Fontan circulation followed in specialist centers, targeting individuals with advanced disease or complications. Follow‐up suggests stabilization of the clinical status after 12 months of therapy.

Lumped parameter models for two-ventricle and healthy and failing extracardiac Fontan circulations

Fontan circulations are surgical strategies to treat infants born with single ventricle physiology. Clinical and mathematical definitions of Fontan failure are lacking, and understanding is needed of parameters indicative of declining physiologies. Our objective is to develop lumped parameter models of two-ventricle and single-ventricle circulations. These models, their mathematical formulations and a proof of existence of periodic solutions are presented. Sensitivity analyses are performed to identify key parameters. Systemic venous and systolic left ventricular compliances and systemic capillary and pulmonary venous resistances are identified as key parameters. Our models serve as a framework to study the differences between two-ventricle and single-ventricle physiologies and healthy and failing Fontan circulations.

Late Fontan failure in adult patients is predominantly associated with deteriorating ventricular function

BACKGROUND

The Fontan operation is a palliative procedure and a substantial number of patients eventually experiences late Fontan circulation failure. Previous concepts of Fontan failure implicate increasing pulmonary vascular resistance (PVR) as a key contributor to late circulatory failure. However, data to support this assumption are sparse. We sought to characterize longitudinal hemodynamic and echocardiographic findings in adult failing Fontan patients.

METHODS

We performed a retrospective cohort study in adult Fontan patients, identifying patients with Fontan failure. Hemodynamic, echocardiographic and clinical data were recorded.

RESULTS

Of 173 adult patients (median follow-up after Fontan 20.2 years [IQR 15.7-24.3]), 48 (28%) showed signs of clinical Fontan failure. Thirty-seven patients (77.1%) exhibited ventricular dysfunction (systolic dysfunction defined by ejection fraction ≤45%, n = 22, or diastolic dysfunction defined by systemic ventricular end-diastolic pressure (SVEDP) ≥12 mmHg, n = 15). Elevated indexed PVR (≥2.5 WU*m²) was only observed in 9 (18.8%) patients. Ejection fraction declined from 60% [IQR 55-65] to 47% [IQR 35-55] during follow-up (p < 0.001). Mean pulmonary artery pressure and SVEDP increased from 11 mmHg [IQR 9-15] to 15 mmHg [IQR 12-18] and from 7 mmHg [IQR 4-10] to 11 mmHg [IQR 8-15] (both p < 0.001), respectively, while indexed PVR did not change significantly (2.1 [IQR 1.1-2.4] vs. 1.7 [IQR 1.1-2.5] WU*m², p = 0.949). Fontan failure-associated mortality during follow-up was substantial (23/48; 48%).

CONCLUSIONS

Systolic and diastolic ventricular dysfunction are frequent features in late Fontan failure in adults, while increases in PVR were rarely observed. The intricate interplay between hemodynamic compromises in Fontan failure deserves further research to optimize treatment strategies and outcome.

Predictors of Poor Functional Status in Adult Fontan Patients Living at Moderate Altitude

Patients who have undergone Fontan palliation have reduced exercise tolerance measured by maximal oxygen consumption (VO₂ max). Declining exercise capacity is associated with increased morbidity and mortality. The impact of hemodynamics and other variables on this population's functional status is not well understood. This study sought to identify variables that predict low VO₂ max in Fontan patients living at moderate altitude (5,000-8,000 feet). We performed a retrospective cohort study of 44 adult Fontan patients living at moderate altitude who had undergone cardiopulmonary exercise testing (CPET) and cardiac catheterization. We evaluated hemodynamic parameters measured during catheterization, imaging results, and laboratory studies for correlation with VO₂ max measured during CPET. Our study cohort (median age 30 years, 52% female) had exercise impairment with mean VO₂ max of 21.6 mL/kg/min. Higher trans-pulmonary gradient (TPG) (p < 0.001) and mean pulmonary artery (PA) pressure (p = 0.013) were predictors of lower maximal and submaximal VO₂. Higher BNP values correlated with lower VO₂ max (p = 0.01). Platelet count, GGT, albumin, and pulmonary vasodilator therapy did not correlate with VO₂ max. None of the studied variables were associated with higher minute ventilation to peak carbon dioxide production (VE/VCO₂ slope) or change in VO₂ max over time. In conclusion, higher TPG and mean PA pressure predicted lower exercise tolerance amongst our cohort of adult Fontan patients living at moderate altitude. Future studies are needed to determine if these clinical variables represent viable therapeutic targets that could result in improved exercise tolerance and outcomes in patients with Fontan circulation.

Pulmonary vascular disease in Fontan circulation-is there a rationale for pulmonary vasodilator therapies?

The Fontan circulation is a palliative concept for patients with univentricular hearts. The central veins are connected directly to the pulmonary arteries (cavo-pulmonary connection) to separate the pulmonary and the systemic circulation. There is no sub-pulmonary ventricle that generates pressure to drive blood through the pulmonary arteries. Pulmonary blood flow is determined by central venous pressure (CVP) and pulmonary vascular resistance (PVR). The capability of the Fontan circulation to compensate for alterations in PVR is limited, as CVP can only be increased within narrow ranges without adverse clinical consequences. Consequently, systemic ventricular preload and cardiac output are dependent on a healthy lung with low PVR. Failure of the Fontan circulation is relatively common. In addition to ventricular dysfunction, maladaptive pulmonary vascular remodeling resulting in increased pulmonary resistance may play a key role. The pathophysiology of the maladaptive vascular processes remains largely unclear and diagnosis of an increased PVR is challenging in Fontan circulation as accurate measurement of pulmonary arterial blood flow is difficult. In the absence of a sub-pulmonary ventricle, pulmonary artery pressure will almost never reach the threshold conventionally used to define pulmonary arterial hypertension. There is a need for markers of pulmonary vascular disease complementary to invasive hemodynamic data in Fontan patients. In order to treat or prevent failure of the Fontan circulation, pathophysiological considerations support the use of pulmonary vasodilators to augment pulmonary blood flow and systemic ventricular preload and lower CVP. However, to date the available trial data have neither yielded enough evidence to support routine use of pulmonary vasodilators in every Fontan patient nor have they been helpful in defining subgroups of patients that might benefit from such therapies. This review discusses potential pathomechanisms of pulmonary vascular disease; it summarizes the current knowledge of the effects and efficacy of pulmonary vasodilator therapy in Fontan patients and tries to outline areas of potential future research on the diagnosis and treatment of pulmonary vascular disease and Fontan failure.

The pulmonary vascular bed in patients with functionally univentricular physiology and a Fontan circulation

Fontan palliation represents one of the most remarkable surgical advances in the management of individuals born with functionally univentricular physiology. The operation secures adult survival for all but a few with unfavourable anatomy and/or physiology. Inherent to the physiology is passive transpulmonary blood flow, which produces a vulnerability to adequate filling of the systemic ventricle at rest and during exertion. Similarly, the upstream effects of passive flow in the lungs are venous congestion and venous hypertension, especially marked during physical activity. The pulmonary vascular bed has emerged as a defining character on the stage of Fontan circulatory behaviour and clinical outcomes. Its pharmacologic regulation and anatomic rehabilitation therefore seem important strategic therapeutic targets. This review seeks to delineate the important aspects of pulmonary artery development and maturation in functionally univentricular physiology patients, pulmonary artery biology, pulmonary vascular reserve with exercise, and pulmonary artery morphologic and pharmacologic rehabilitation.

Reaching consensus for unified medical language in Fontan care

Aims

The Fontan operation has resulted in improved survival in patients with single‐ventricle congenital heart disease. As a result, there is a growing population of teenagers and adults with a Fontan circulation. Many co‐morbidities have been increasingly recognized in this population due to the unique features of the Fontan circulation. Standardization of how Fontan co‐morbid conditions are defined will help facilitate understanding, consistency and interpretability of research and clinical experience. Unifying common language usage in Fontan is a critical precursor step for data comparison of research findings and clinical outcomes and ultimately accelerating improvements in management for this growing group of patients. This manuscript aimed to create unified definitions for morbidities seen after the Fontan palliation.

Methods

In association of many congenital heart disease organizations, this work used Delphi methodology to reach a broad consensus among recognized experts regarding commonly used terms in Fontan care and research. Each definition underwent at least three rounds of revisions to reach a final definition through surveys sent to experts in the field of single‐ventricle care.

Results

The process of reaching a consensus on multiple morbidities associated with the Fontan procedure is summarized in this manuscript. The different versions that preceded reaching the consensus are also presented in the Supporting Information. Table 1 represents the final definitions according to the consensus.

Conclusions

We propose the use of these definitions for clinical care, future research studies, registry development and clinical trials.

Does Maintenance of Pulmonary Blood Flow Pulsatility at the Time of the Fontan Operation Improve Hemodynamic Outcome in Functionally Univentricular Hearts?

It is unclear whether residual anterograde pulmonary blood flow (APBF) at the time of Fontan is beneficial. Pulsatile pulmonary flow may be important in maintaining a compliant and healthy vascular circuit. We, therefore, wished to ascertain whether there was hemodynamic evidence that residual pulsatile flow at time of Fontan promotes clinical benefit. 106 consecutive children with Fontan completion (1999-2018) were included. Pulmonary artery pulsatility index (PI, (systolic pressure-diastolic pressure)/mean pressure)) was calculated from preoperative cardiac catheterization. Spectral analysis charted PI as a continuum against clinical outcome. The population was subsequently divided into three pulsatility subgroups to facilitate further comparison. Median PI prior to Fontan was 0.236 (range 0-1). 39 had APBF, in whom PI was significantly greater (median: 0.364 vs. 0.177, Mann-Whitney p < 0.0001). There were four early hospital deaths (3.77%), and PI in these patients ranged from 0.214 to 0.423. There was no correlation between PI and standard cardiac surgical outcomes or systemic oxygen saturation at discharge. Median follow-up time was 4.33 years (range 0.0273-19.6), with no late deaths. Increased pulsatility was associated with higher oxygen saturations in the long term, but there was no difference in reported exercise tolerance (Ross), ventricular function, or atrioventricular valve regurgitation at follow-up. PI in those with Fontan-associated complications or the requiring pulmonary vasodilators aligned with the overall population median. Maintenance of pulmonary flow pulsatility did not alter short-term outcomes or long-term prognosis following Fontan although it tended to increase postoperative oxygen saturations, which may be beneficial in later life.

Peripheral venous pressure changes during exercise are associated with adverse Fontan outcomes

OBJECTIVE

Elevated central venous pressure (CVP) plays an important role in the development of adverse Fontan outcomes. Peripheral venous pressure (PVP) has been validated as a surrogate for CVP in Fontan patients. We hypothesised that PVP in response to exercise will be associated with a greater prevalence of Fontan morbidity.

METHODS

Adult Fontan patients had cardiopulmonary exercise testing (CPET) with PVP monitoring in the upper extremity between 2015 and 2018. PVP at rest, during unloaded cycling and at peak exercise was compared between those with and without adverse Fontan outcomes including arrhythmia, unscheduled hospital admissions, heart failure requiring diuretics, need for reintervention and a composite outcome of the above morbidities, heart transplantation and death.

RESULTS

Forty-six patients with a mean age at CPET of 26.9±9.5 years. During exercise, PVP increased from 13.6±3.5 mm Hg at rest, to 16.5±3.9 mm Hg during unloaded cycling, to 23.0±5.5 mm Hg at peak exercise. Unloaded and peak PVP were more strongly associated than resting PVP with all adverse outcomes, except reintervention (composite outcome: resting PVP: OR 2.8, p=0.023; unloaded PVP: OR 6.1, p=0.001; peak PVP: OR 4.0, p<0.001). Cut-offs determined using ROC curve analysis had high specificity for the composite outcome (88% unloaded PVP ≥18 mm Hg; 89% peak PVP ≥25 mm Hg).

CONCLUSION

Higher PVP at unloaded and peak exercise was strongly associated with a higher prevalence of adverse Fontan outcomes. Minimally invasive PVP monitoring during CPET may serve as a useful tool for risk stratifying individuals with a Fontan.

Assessing Single Ventricle Function in the Fontan Circulation using Wave Intensity Analysis

Single ventricle hearts palliated with the Fontan operation present complications later in life as a result of increased venous pressures and abnormal ventricle function. Wave intensity analysis uses measurements of blood velocity and pressure to represent arterial hemodynamics as summations of energy waves. This methodology could potentially be a useful tool in assessment of Fontan patients. The clinical value of wave intensity parameters was utilized to evaluate the functional performance of the single ventricle in Fontan patients. A retrospective analysis of invasive hemodynamic data was retrospectively obtained from routine cardiac catheterization of patients with Fontan circulation (n = 20) and comparison to those with biventricular circulation (n = 10) who presented to the catheterization laboratory for closure of small patent ductus arteriosus (PDAs). Wave intensity analysis and wave energy flux was calculated using aortic pressure waveforms and echocardiography aortic Doppler measurements as previously described. Significant differences were seen in the peak forward compression wave (p = 0.013), early systolic energy flux (p = 0.005) and the systolic and diastolic ratio (p = 0.006) in Fontan patients versus controls. Within the Fontan group, there was a positive correlation (0.54, p = 0.02) between the wave speed and pulmonary vascular resistance. Early systolic energy flux was a potential individual indicator of a Fontan patients heart failure classification (AUC = 0.71). Wave intensity analysis could be a useful tool in screening Fontan patients and predicting clinical outcomes and Fontan failure. Future prospective analyses of Fontan hemodynamics and WIA are needed.