Fontan Circulation

This is a multicenter, observational, cross-sectional study designed to investigate whether a parsimonious set of low-cost, accessible functional, anthropometric, and physiological measurements can help identify multisystem clinical-physiological impairment in patients with Fontan circulation. Fontan circulation is associated with long-term multisystem complications affecting cardiac, cardiopulmonary, hepatic, renal, nutritional-lymphatic, hematological, and metabolic function. Current surveillance may require multiple specialized, costly, and time-consuming investigations. This study will explore whether simple and easily repeatable measurements can provide an accessible complementary approach for the initial functional and clinical assessment of these patients. Approximately 150 participants aged 14 to 60 years with Fontan circulation, recruited from 18 Spanish healthcare centers, will be included. Participants must have undergone Fontan surgery at least 2 years before inclusion and be clinically stable in outpatient follow-up. Each participant will attend one study-specific visit lasting approximately 45-60 minutes. During this visit, functional, anthropometric, and physiological variables will be assessed. Functional measurements will include squat jump performance using the Samozino method and the five-times sit-to-stand test (5xSTS) using the Alcázar method. Anthropometric measurements will include body mass index, age- and sex-adjusted anthropometric indicators of muscularity, and calf and thigh circumferences. Physiological measurements will include resting heart rate and oxygen saturation, heart rate recovery after the 1-minute sit-to-stand test, and post-exercise oxygen saturation. Clinical, laboratory, echocardiographic, and functional data obtained as part of routine clinical follow-up will also be collected. Whenever possible, routine clinical measurements will correspond to assessments performed on the same day as the functional evaluation; measurements obtained within a maximum window of ±15 days will also be considered. The primary analysis will evaluate the association between the candidate low-cost measurements and the presence of clinical-physiological impairment affecting two or more organ or functional domains. Additional analyses will investigate their ability to identify patients with impairment in at least one domain and to discriminate increasing levels of multisystem clinical-physiological burden. The study will not involve any therapeutic intervention or prospective study-specific follow-up. The results will be interpreted as cross-sectional associations and will not establish causal or longitudinal prognostic relationships.

The aim of this study is to investigate whether venous compression garments increase exercise stroke volume in patients with Fontan circulation. To address this aim, we will test the following hypotheses: 1. Acute and chronic external venous compression will increase exercise stroke volume in patients with Fontan circulation. 2. Patients with significant venous varicosities will have a greater response to venous compression. Participants will: * Undergo submaximal exercise testing in MRI to measure venous return and exercise stroke volume with and without the wearing of compression garments * Undergo submaximal exercise testing on a seated upright exercise ergometer with concurrent measurement of stroke volume with and without the wearing of compression garments * A subset of participants will repeat both testing visits after wearing compression garments for 2-weeks during waking hours. Participants will: * Undergo submaximal exercise testing in MRI to measure venous return and exercise stroke volume with and without the wearing of compression garments * Undergo submaximal exercise testing on a seated upright exercise ergometer with concurrent measurement of stroke volume with and without the wearing of compression garments * A subset of participants will repeat both testing visits after wearing compression garments for 2-weeks during waking hours.

The purpose of this research is to determine whether treatment with the study drug dapagliflozin for 3 months affects peripheral venous pressure at rest and during exercise in adults with failing Fontan circulation.

This is a single center, open-label, prospective, investigation to quantify the effects liver congestion and fibrosis has on hepatic drug metabolism and transport in children, adolescents, and young adults with Fontan circulation.

In the Swedish registry for congenital heart defects, SWEDCON, over 230 patients with single-ventricle circulation are registered in the adult section. Congenital heart defects affect career choices, family planning, and leisure activities. Questions regarding heredity and pregnancy are common. The impact of Fontan circulation on reproductive health and fertility needs to be illuminated, and additional studies are required from both medical and psychosocial perspectives.Cognitive impairment is common among patients with congenital heart defects but is likely an overlooked cause of long-term illness. Objective To study a large national population (n=200) of adults with Fontan circulation and their potential partners regarding. * the prevalence and explanatory factors for sexual dysfunction and infertility in women and men with Fontan circulation (Study A). * the outcomes of pregnancy, choice of delivery mode, and complications in patients with Fontan circulation (Study B). * the experiences and perceptions of becoming parents among women (n=20) and men (n=20), as well as elucidate reasoning and family planning among women and men (n=20) who have not become parents (Study C). * Investigate the prevalence and explanatory factors for (Sub-study D): * Fatigue * In-depth cognitive screening to describe specific cognitive functions such as auditory memory, visuospatial memory, attention, cognitive speed, and executive functions. The aim of this research is to gain more knowledge in an area that has been relatively underexplored, thus improving care for women and men with congenital heart defects.