Towards the goal of achieving a normal duration and quality of life after Fontan operation: Creation of the International Fontan Interest group (I-FIG), an international collaborative initiative dedicated to improving outcomes

Characterization and z-score calculation of cardiovascular magnetic resonance imaging parameters in patients after the Fontan operation: A Fontan Outcome Registry using Cardiovascular Magnetic Resonance Examinations study

BACKGROUND

Cardiac magnetic resonance (CMR) offers valuable hemodynamic insights post-Fontan, but is limited by the absence of normative single ventricle data. The Fontan Outcomes Registry using CMR Examinations (FORCE) is a large international Fontan-specific CMR registry. This study used FORCE registry data to evaluate expected CMR ventricular size/function and create Fontan-specific z-scores adjusting for ventricular morphology (VM) in healthier Fontan patients.

METHODS

"Healthier" Fontan patients were defined as patients free of adverse outcomes, who are New York Heart Association class I, have mild or less valve disease, and <30% aortopulmonary collateral burden. General linear modeling was performed on 70% of the dataset to create z-scores for volumes and function. Models were tested using the remainder (30%) of the data. The z-scores were compared between children and adults. The z-scores were also compared between "healthier" Fontan and patients with adverse outcomes (death, listing for transplantation, or multiorgan disease).

RESULTS

The "healthier" Fontan population included 885 patients (15.0 ± 7.6 years) from 18 institutions with 1156 CMR examinations. Patients with left ventricle morphology had lower volume, mass and higher ejection fraction (EF) compared to right or mixed (two ventricles) morphology (p < 0.001 for all pairwise comparisons). Gender, body surface area, and VM were used in z-scores. Of the "healthier" Fontan patients, 647 were children <18 years and 238 were adults. Adults had lower ascending aorta flow (2.9 ± 0.7 vs 3.3 ± 0.8 L/min/m2, p < 0.001) and ascending aorta flow z-scores (-0.16 ± 1.23 vs 0.05 ± 0.95, 0.02) compared to children. Additionally, there were 1595 patients with adverse outcomes who were older (16.1 ± 9.3 vs 15.0 ± 7.6, p < 0.001) and less likely to have left VM (35 vs 47%, p < 0.001). Patients with adverse outcomes had higher z-scores for ventricular volume and mass and lower z-scores for EF and ascending aorta flow compared to the "healthier" Fontan cohort.

CONCLUSION

This is the first study to generate CMR z-scores post-Fontan. Importantly, the z-scores were generated and tested in "healthier" Fontan patients and both pediatric and adult Fontan patients. These equations may improve CMR-based risk stratification after the Fontan operation.

Current Understanding and Future Directions of Transcatheter Devices to Assist Failing Fontan

Even if the Fontan operation is the surgical treatment of choice in patients with univentricular physiology, it remains a palliative strategy. Consequently, when Fontan patients reach adulthood, the majority of them develop late clinical sequelae of a failing cavo-pulmonary circuit (eg, liver failure, protein-losing enteropathy, and arrhythmias). Although heart transplantation represents the gold standard to treat this condition, Fontan patients usually accede to this therapy late, when risk of mortality is significantly increased, and a shortage of donor hearts limits transplantation in this special population. Mechanical circulatory support is an emerging field, but it is still in the experimental stage. Current mechanical circulatory devices have been used in Fontan circulation but are associated with the need for high-risk redo surgery. Percutaneous pumps are an emerging field that is still under investigation, with multiple prototypes developed. This review aims to analyze the hemodynamic profile of the developed intravascular pumps and their application in the preclinical scenario in the Fontan circulation.

Hemodynamic Effect of a Fontan Assist Device on a Numerical Fontan Circulatory Model under Various Medication Scenarios

Patients with single-ventricle heart disease and failing Fontan circulation represent the largest and most rapidly growing subgroup of adults with congenital heart disease referred for transplant assessment. Few clinical therapies are available for improving Fontan hemodynamics. Mechanical circulatory support devices have been used successfully in the clinical setting to assist the single ventricle, but no device is currently available to support the subpulmonary circulation. A subpulmonary pump could be used to support patients with failing Fontan circulation by mitigating chronic venous hypertension and restoring normal physiology. Our group designed a Fontan assist device (FAD) to augment right-heart (subpulmonary) flow and decrease venous pressures. To ensure that our FAD could achieve target hemodynamic parameters, we developed a numerical Fontan circulatory model to evaluate the interaction between the cardiovascular system and the FAD. To ensure that the circulatory model can mimic real-world clinical conditions, we investigated the effects of various medications in the FAD loop. Results showed that the FAD can significantly increase cardiac output in Fontan patients and can create a pressure difference between the pulmonary arteries and venae cavae. Further, the systemic venous pressure can be significantly reduced by using the FAD plus diuretic treatment. The downstream pulmonary artery pressure can be increased by augmenting the FAD with vasodilator treatment, diuretic treatment, or both.Clinical Relevance- This work supports FAD development by providing a method for studying human cardiovascular effects under various hemodynamic scenarios.

Serial assessment of somatic and cardiovascular development in patients with single ventricle undergoing Fontan procedure

BACKGROUND

The palliation of patients with single ventricle (SV) undergoing Fontan procedure led to improved long-term survival but is still limited due to cardiovascular complications. The aim of this study was to describe the somatic and cardiovascular development of Fontan patients until adolescence and to identify determining factors.

METHODS

We retrospectively assessed somatic growth, vascular growth of pulmonary arteries, and cardiac growth of the SV and systemic semilunar valve from 0 to 16 years of age using transthoracic echocardiography. The Doppler inflow pattern of the atrioventricular valve was quantified by E-, A-wave and E/A ratio. All data were converted to z-scores and analyzed using linear mixed effect models to identify associations with age at Fontan procedure, gender, and ventricular morphology.

RESULTS

134 patients undergoing Fontan procedure at a median age of 2.4 (IQR 2.12 to 2.8) years were analyzed. A catch-up of somatic growth after Fontan procedure until school age was found, with lower body height and weight z-scores in male patients and patients with systemic right ventricles. An early time of Fontan procedure was favorable for somatic growth, but not for vascular growth. Cardiac development indicated a decrease of SV end-diastolic diameter z-score until adolescence. Despite a trend towards normalization, E-wave and E/A ratio z-scores were diminished over the entire period.

CONCLUSIONS

There is a catch-up growth of somatic, vascular and cardiac parameters after Fontan procedure, which in our cohort depends on the time of Fontan procedure, ventricular morphology, and gender. Beside other factors, diastolic function of the SV remains altered.

Staged total cavopulmonary connection: serial comparison of intra-atrial lateral tunnel and extracardiac conduit taking account of current surgical adaptations

OBJECTIVES

Our goals were to compare the outcome of the intra-atrial lateral tunnel (ILT) and the extracardiac conduit (ECC) techniques for staged total cavopulmonary connection (TCPC) and to compare the current modifications of the TCPC technique, i.e. the prosthetic ILT technique with the current ECC technique with a ≥18-mm conduit.

METHODS

We included patients who had undergone a staged TCPC between 1988 and 2008. Records were reviewed for patient demographics, operative details and events during follow-up (death, surgical and catheter-based reinterventions and arrhythmias).

RESULTS

Of the 208 patients included, 103 had the ILT (51 baffle, 52 prosthetic) technique and 105 had the ECC technique. Median follow-up duration was 13.2 years (interquartile range 9.5-16.3). At 15 years after the TCPC, the overall survival rate was comparable (81% ILT vs 89% ECC; P = 0.12). Freedom from late surgical and catheter-based reintervention was higher for patients who had ILT than for those who had ECC (63% vs 44%; P = 0.016). However, freedom from late arrhythmia was lower for patients who had ILT than for those who had ECC (71% vs 85%, P = 0.034). In a subgroup of patients who had the current TCPC technique, when we compared the use of a prosthetic ILT with ≥18-mm ECC, we found no differences in freedom from late arrhythmias (82% vs 86%, P = 0.64) or in freedom from late reinterventions (70% vs 52%, P = 0.14).

CONCLUSIONS

A comparison between the updated prosthetic ILT and current ≥18-mm ECC techniques revealed no differences in late arrhythmia-free survival or late reintervention-free survival. Overall, outcomes after the staged TCPC were relatively good and reinterventions occurred more frequently in the ECC group, whereas late arrhythmias were more common in the ILT group.

Research priorities in single-ventricle heart conditions: a United Kingdom national study

OBJECTIVE

To bring together stakeholders in the United Kingdom to establish national priorities for research in single-ventricle heart conditions.

METHODS

This study comprised two surveys and a workshop. The initial public online survey asked respondents up to three questions they would like answered for research. Responses were classified as unanswered, already answered, or unable to be answered by scientific research. In the follow-up survey, unanswered questions were divided into categories and respondents were asked to rank categories and questions by priority. A stakeholder workshop attended by patients, parents, healthcare professionals, researchers, and charities was held to determine the final list of research priorities.

RESULTS

A total of 128 respondents posed 344 research questions, of which 271 were classified as unanswered, and after removing duplicates, 204 questions remained, which were divided into 20 categories. In the second survey, 56 (49.1%) respondents successfully ranked categories and questions. A total of 39 participants attended the workshop, drawing up a list of 30 research priorities across nine priority categories. The nine priority categories are: Associated co-morbidities; Brain &amp; neurodevelopment; Exercise; Fontan failure; Heart function; Living with a single ventricle heart condition; Management of the well-functioning Fontan circulation; Surgery &amp; perioperative care; and Transplantation, mechanical support &amp; novel therapies.

CONCLUSIONS

Through a multi-stage process, we engaged a wide range of interested parties to establish a list of research priorities in single-ventricle heart conditions. This provides a platform for clinicians, researchers, and funders in the United Kingdom and elsewhere to address the most important questions and improve outcomes in these rare but high-impact CHDs.