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.

Detection of severe congenital heart defects in live-born infants in Norway 2017-2020.

AIM: The aims of this nationwide retrospective cohort study were to determine the time and causes of detection of severe congenital heart defects (CHDs) in live-born infants in Norway between 2017 and 2020. METHODS: Information regarding live-born infants with severe CHDs was retrieved from national registries and medical records. RESULTS: A total of 219 776 infants were born in Norway from 01.01.2017 to 31.12.2020. Severe CHDs were diagnosed in 442 (0.2%) infants. Of these, 376 (85%) infants were diagnosed either prenatally (n = 203, 46%) or before discharge from hospital after birth (n = 173, 39%). A total of 56 (13%) infants were discharged with undetected CHDs. Time of detection was unknown in 10 cases (2%). The most frequent undetected CHDs at discharge were coarctation of the aorta/aortic arch hypoplasia (n = 24), atrioventricular septal defect (n = 13), anomalous pulmonary venous connection (n = 5) and coronary artery anomalies (n = 4). Seven (13%) children with undetected CHD experienced circulatory collapse out of hospital. CONCLUSION: Most infants with severe CHDs in Norway were identified prior to hospital discharge. However, some infants were discharged undiagnosed. Awareness of undetected CHDs and immediate cardiac assessment in infants with signs of circulatory failure early in life are still important.

Preoperative versus postoperative survival in patients with univentricular heart: a nationwide, retrospective study of patients born in 1990-2015.

OBJECTIVES: Few data exist on mortality among patients with univentricular heart (UVH) before surgery. Our aim was to explore the results of intention to perform surgery by estimating preoperative vs postoperative survival in different UVH subgroups. DESIGN: Retrospective. SETTING: Tertiary centre for congenital cardiology and congenital heart surgery. PARTICIPANTS: All 595 Norwegian children with UVH born alive from 1990 to 2015, followed until 31 December 2020. RESULTS: One quarter (151/595; 25.4%) were not operated. Among these, only two survived, and 125/149 (83.9%) died within 1 month. Reasons for not operating were that surgery was not feasible in 31.1%, preoperative complications in 25.2%, general health issues in 23.2% and parental decision in 20.5%. In total, 327/595 (55.0%) died; 283/327 (86.5%) already died during the first 2 years of life. Preoperative survival varied widely among the UVH subgroups, ranging from 40/65 (61.5%) among patients with unbalanced atrioventricular septal defect to 39/42 (92.9%) among patients with double inlet left ventricle. Postoperative survival followed a similar pattern. Postoperative survival among patients with hypoplastic left heart syndrome (HLHS) improved significantly (5-year survival, 42.5% vs 75.3% among patients born in 1990-2002 vs 2003-2015; p<0.0001), but not among non-HLHS patients (65.7% vs 72.6%; p=0.22)-among whom several subgroups had a poor prognosis similar to HLHS. A total of 291/595 patients (48.9%) had Fontan surgery CONCLUSIONS: Surgery was refrained in one quarter of the patients, among whom almost all died shortly after birth. Long-term prognosis was largely determined during the first 2 years. There was a strong concordance between preoperative and postoperative survival. HLHS survival was improved, but non-HLHS survival did not change significantly. This study demonstrates the complications and outcomes encountering newborns with UVH at all major stages of preoperative and operative treatment.

Real-time Remote Expert-guided Echocardiography by Medical Students.

BACKGROUND: Echocardiography is a highly specialised examination performed by experienced healthcare professionals. These experienced healthcare professionals may not be available to patients during all hours in rural healthcare facilities. Remote-guided echocardiography could improve the availability of specialised care for patients living in rural areas. This study examined the feasibility of real-time remote guidance for medical students to perform an echocardiographic assessment of the left side of the heart. Thirteen healthy volunteers were recruited for remote-guided echocardiography, which was performed by 13 medical students. Student examinations/images were compared to reference echocardiography. Measurements of left ventricular fractional shortening and mitral valve blood flow velocity were also compared. Furthermore, guidance through a smartphone videoconference was compared to designated remote guidance software. RESULTS: Two-thirds of the images acquired by students were rated as medium or good quality and usable to evaluate two thirds of the cardiac structures. No significant bias was found for left ventricular fractional shortening. The measurements from the students' exams had a variation coefficient of 14.8% compared to the reference. The calculated deviation of the insonation angle was above 25° for both E and A-wave mitral valve blood flow velocity measurements. Images acquired by guidance through smartphone videoconference were of lower quality than those obtained using the designated remote guidance software. CONCLUSION: Real-time remote-guided echocardiography performed by medical students has limited value for clinical screening but could be useful for educational purposes.

Acceptability and Initial Adoption of the Heart Observation App for Infants With Congenital Heart Disease: Qualitative Study.

BACKGROUND: Approximately 1% of all infants are born with a congenital heart disease (CHD). Internationally CHD remains a major cause of infant death, some of which occur unexpectedly after a gradual deterioration at home. Many parents find it difficult to recognize worsening of symptoms. OBJECTIVE: This study aims to report the acceptability and initial adoption of a mobile app, the Heart Observation app (HOBS), aiming to support parents' understanding and management of their child's condition and to increase quality in follow-up from health care professionals in complex health care services in Norway. METHODS: A total of 9 families were interviewed on discharge from the neonatal intensive care unit and after 1 month at home. The infant's primary nurse, community nurse, and cardiologist were also interviewed regarding their experiences about collaboration with the family. The interviews were analyzed inductively with thematic content analysis. RESULTS: The analysis generated 4 main themes related to acceptability and adoption: (1) Individualize Initial Support, (2) Developing Confidence and Coping, (3) Normalize When Appropriate, and (4) Implementation in a Complex Service Pathway. The receptivity of parents to learn and attend in the intervention differs according to their present situation. Health care professionals emphasized the importance of adapting the introduction and guidance to parents' receptivity to ensure comprehension, self-efficacy, and thereby acceptance before discharge (Individualize Initial Support). Parents perceived that HOBS served them well and nurtured confidence by teaching them what to be aware of. Health care professionals reported most parents as confident and informed. This potential effect increased the possibility of adoption (Developing Confidence and Coping). Parents expressed that HOBS was not an "everyday app" and wanted to normalize everyday life when appropriate. Health care professionals suggested differentiating use according to severity and reducing assessments after recovery to adapt the burden of assessments when appropriate (Normalize When Appropriate). Health care professionals' attitude to implement HOBS in their services was positive. They perceived HOBS as useful to systemize guidance, to enhance communication regarding an infant's condition, and to increase understanding of heart defects in health care professionals with sparse experience (Implementation in a Complex Service Pathway). CONCLUSIONS: This feasibility study shows that both parents and health care professionals found HOBS as a positive addition to the health care system and follow-up. HOBS was accepted and potentially useful, but health care professionals should guide parents initially to ensure comprehension and adapt timing to parents' receptivity. By doing so, parents may be confident to know what to look for regarding their child's health and cope at home. Differentiating between various diagnoses and severity is important to support normalization when appropriate. Further controlled studies are needed to assess adoption, usefulness, and benefits in the health care system.

In Silico Evaluation of a Self-powered Venous Ejector Pump for Fontan Patients.

PURPOSE: The Fontan circulation carries a dismal prognosis in the long term due to its peculiar physiology and lack of a subpulmonic ventricle. Although it is multifactorial, elevated IVC pressure is accepted to be the primary cause of Fontan's high mortality and morbidity. This study presents a self-powered venous ejector pump (VEP) that can be used to lower the high IVC venous pressure in single-ventricle patients. METHODS: A self-powered venous assist device that exploits the high-energy aortic flow to lower IVC pressure is designed. The proposed design is clinically feasible, simple in structure, and is powered intracorporeally. The device's performance in reducing IVC pressure is assessed by conducting comprehensive computational fluid dynamics simulations in idealized total cavopulmonary connections with different offsets. The device was finally applied to complex 3D reconstructed patient-specific TCPC models to validate its performance. RESULTS: The assist device provided a significant IVC pressure drop of more than 3.2 mm Hg in both idealized and patient-specific geometries, while maintaining a high systemic oxygen saturation of more than 90%. The simulations revealed no significant caval pressure rise (< 0.1 mm Hg) and sufficient systemic oxygen saturation (> 84%) in the event of device failure, demonstrating its fail-safe feature. CONCLUSIONS: A self-powered venous assist with promising in silico performance in improving Fontan hemodynamics is proposed. Due to its passive nature, the device has the potential to provide palliation for the growing population of patients with failing Fontan.

Heart OBServation app: development of a decision support tool for parents of infants with severe cardiac disease.

BACKGROUND AND OBJECTIVES: Many parents of infants with CHD find it difficult to recognise symptoms of deterioration in their children. Therefore, a personalised decision support application for parents has been developed. This application aims to increase parents' awareness of their infant's normal condition, help them assess signs of deterioration, decide who and when to contact health services, and what to report. The aim of this paper is to describe the concept and report results from a usability study. METHODS: An interprofessional group developed a mobile application called the Heart OBServation app in close collaboration with parents using an iterative process. We performed a usability study consisting of semi-structured interviews of 10 families at discharge and after one month and arranged two focus group interviews with nurses caring for these families. A thematic framework analysis of the interviews explored the usability of features in the application. Usability was assessed twice using the System Usability Scale, and a user log was registered throughout the study. RESULTS: The overall system usability score, 82.3 after discharge and 81.7 after one month, indicates good system usability. The features of Heart OBServation were perceived as useful to provide tailored information, increase awareness of the child's normal condition, and to guide parents in what to look for. To empower parents, an interactive discharge checklist was added. CONCLUSIONS: The Heart OBServation demonstrated good usability and was well received by parents and nurses. Feasibility and benefits of this application in clinical practice will be investigated in further studies.

Current outcomes of live-born children with double outlet right ventricle in Norway.

OBJECTIVES: This population-based, comprehensive, retrospective study presented the clinical outcomes of all children born in Norway between 2003 and 2017 with double outlet right ventricle (DORV). METHODS: All children born with DORV between 2003 and 2017 were identified in the Oslo University Hospital registry. Patients' characteristics, interventions, complications and deaths were recorded. Echocardiographic data were reviewed for classification according to current standards. We investigated time-dependent surgical reintervention and mortality using Kaplan-Meier analyses and determinants of treatment complications, reintervention and death using regression analyses. RESULTS: Ninety-three children with DORV represented an annual median prevalence of 1.18 per 10 000 births in Norway. Six children received palliative care. With an intention to treat, a surgical route with the primary biventricular repair was followed for 62 children, staged biventricular repair for 15 and univentricular repair for 10 children. Major complications occurred in 1.0% and 6.2% of children following catheter or surgical intervention, respectively. No significant determinants of the complications were identified. Overall survival following treatment was 91.9%, 90.8%, 89.5% and 89.5% and corresponding freedom from surgical reintervention was 88.0%, 79.0%, 74.9% and 69.4% at 1, 2, 5 and 10 years, respectively. The presence of atrioventricular septal defect predicted an increased risk of mortality (hazard ratio: 7.16) but did not increase the risk of surgical reintervention. CONCLUSIONS: In Norway, most children receive tailored treatment for DORV with low rates of complications, surgical reinterventions and mortality. However, atrioventricular septal defect remains a potential determinant of postoperative death.

Neonatal interstitial lung disease in a girl with Jacobsen syndrome: a case report.

BACKGROUND: We report a case of the neonatal interstitial lung disease pulmonary interstitial glycogenosis in a girl with Jacobsen syndrome. While Jacobsen syndrome is caused by a deletion on the long arm of chromosome 11 and is genetically confirmed, pulmonary interstitial glycogenosis is of unknown etiology and is diagnosed by lung biopsy. Pulmonary interstitial glycogenosis has not previously been described in association with Jacobsen syndrome. CASE PRESENTATION: A term newborn small for gestational age Caucasian girl presented with respiratory distress, pulmonary hypertension, congenital heart defects, immunodeficiency, and thrombocytopenia. She was diagnosed with Jacobsen syndrome, but also had pulmonary interstitial glycogenosis, which contributed to significant morbidity. There was striking clinical improvement after steroid treatment of the pulmonary interstitial glycogenosis. CONCLUSIONS: Interstitial lung disease should be considered as a differential diagnosis when respiratory distress and hypoxemia in the perinatal period worsens or persists despite standard treatment. Importantly, pulmonary interstitial glycogenosis may be treatable with corticosteroids. Whether there is a genetic link between pulmonary interstitial glycogenosis and Jacobsen syndrome is still unknown.

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 (VO2peak) 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 VO2peak 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.

Spectrum of Fontan-associated liver disease assessed by MRI and US in young adolescents.

PURPOSE: Patients with Fontan circulation are at risk of developing hepatic fibrosis/cirrhosis. The mechanisms and disease development are unclear and early secondary liver cancer is a concern. This study will describe hepatic imaging findings in a national cohort of adolescents with Fontan circulation. METHODS: The patients prospectively underwent abdominal contrast enhanced magnetic resonance imaging (MRI) including diffusion-weighted imaging. Images were assessed for criteria of fibrosis/cirrhosis including characterization of hepatic nodules. These nodules were in addition, assessed by ultrasonography (US). Nodules ≥ 1 cm were investigated and monitored to evaluate malignant transformation. Clinical and hepatic serological data were recorded. RESULTS: Forty-six patients, median age of 16.5 years (15.4-17.9 years) were enrolled. All patients underwent US examination and MRI was performed in 35/46 patients. On MRI, 60% had hepatomegaly and 37% had signs of fibrosis/cirrhosis. Seven patients had together 13 nodules ≥ 1 cm in diameter. Only 4/13 (17%) where seen on US. Nodules had variable MRI signal characteristics including hepatobiliary contrast enhancement and two nodules revealed portal venous phase 'wash-out' on the first examination. No further imaging signs of malignancy were revealed during the follow-up period of median 24.4 (7-42) months. CONCLUSION: The majority of adolescents with Fontan circulation had imaging findings of fibrosis/cirrhosis of varying severity. US had low detection rate of hepatic nodules compared to MRI. The imaging work-up before transition to adult cardiology care did not reveal findings suggestive of malignancy. However, the high prevalence of Fontan-associated liver disease calls for surveillance strategies even in childhood.

Unexpected death in children with severe congenital heart defects in Norway 2004-2016.

AIMS: Updated knowledge on the rates and causes of death among children with severe congenital heart defects (CHDs) is needed to further improve treatment and survival. This study investigated nationwide mortality rates in children with severe CHDs with an emphasis on unexpected mortality unrelated to cardiac intervention. METHODS AND RESULTS: Data on all pregnancies and live-born children in Norway from 2004 to 2016 were obtained from national registries, the Oslo University Hospital's Clinical Registry for CHDs and medical records. Among 2359 live-born children with severe CHDs, 234 (10%) died before 2 years of age. Of these, 109 (46%) died in palliative care, 58 (25%) died of causes related to a cardiac intervention and 67 (29%) died unexpectedly and unrelated to a cardiac intervention, either before (n=26) or following (n=41) discharge after a cardiac intervention. Comorbidity (38/67, 57%), persistent low oxygen saturation (SaO2; <95%; 41/67, 61%), staged surgery (21/41, 51%), residual cardiac defects (22/41, 54%) and infection (36/67, 54%) were frequent in children who died unexpectedly unrelated to an intervention. Two or more of these factors were present in 62 children (93%). The medical reports at hospital discharge lacked information on follow-up in many patients who died unexpectedly. CONCLUSIONS: The numbers of unexpected deaths unrelated to cardiac intervention in children <2 years of age without comorbidity were low in Norway. However, close follow-up is recommended for infants with comorbidities, persistent low oxygen saturation, staged surgery or residual cardiac defects, particularly when an infection occurs.

Severe congenital heart defects: incidence, causes and time trends of preoperative mortality in Norway.

BACKGROUND AND AIMS: Severe congenital heart defects (CHDs) still represent one of the main causes of infant death. The risk factors associated with cardiac surgery and postoperative mortality are well known. We aimed to describe the rates, causes and time trends of mortality before surgery-including termination of pregnancies and palliative care-in fetuses and children below 2 years of age with severe CHDs. METHODS AND RESULTS: Data concerning all 789 345 pregnancies in Norway from 2004 to 2016 were retrieved from the Medical Birth Registry of Norway, the Oslo University Hospital's Clinical Registry for Congenital Heart Defects, the Norwegian Cause of Death Registry, the National Registry, Statistics Norway, autopsy reports and medical records. When including termination of pregnancy and stillbirths, the number of fetuses and children with severe CHDs that did not reach the age of 2 years was 31%. Mortality among the 2359 live-born infants with severe CHDs was 10%, of whom 58% died before surgery. Of the preoperative deaths, 81% died in a palliative care setting, and comorbidity and univentricular CHDs were common among these infants. Together, palliative care and termination of pregnancy accounted for 86% of deaths in cases of severe CHDs, and this proportion increased during the study period (annual percent changes 1.3, 95% CI 0.4 to 2.1, p<0.001), mainly due to an increased termination rate. CONCLUSIONS: Termination of pregnancy accounted for the majority of the deaths in fetuses and children with severe CHDs. Among live-born children, most preoperative deaths occurred in a palliative care setting and were strongly related to comorbidities and/or univentricular hearts.

Diagnosis of severe congenital heart defects in Norway 2016. / Diagnostikk av alvorlige medfødte hjertefeil i Norge 2016.

BACKGROUND: Most structural congenital heart defects can be identified prenatally through ultrasound examination in pregnancy or via routine examinations during hospital maternity stays, but in some cases, heart defects are not discovered prior to discharge. There has been little previous research into detection rates with the various methods available. In this study, we have examined the timing and method of diagnosis of severe congenital heart defects. MATERIAL AND METHOD: All children with severe heart defects born in Norway in 2016 and registered at Oslo University Hospital were included in this study. In addition, information on committee-handled abortions (after the 12th week of pregnancy) was obtained from the Medical Birth Registry of Norway. RESULTS: In total, 105 of 181 (58 %) severe heart defects were diagnosed prenatally, and 51 (28 %) pregnancies were terminated. Among the 73 live-born children with severe heart defects that went unrecognised prenatally, 33 (45 %) of the heart defects were discovered outside of routine examinations and 9 (12 %) after discharge from hospital. Coarctation of the aorta was the most common diagnosis in cases of late-detected heart defects. INTERPRETATION: This first national study of the diagnosis of severe congenital heart defects in Norway shows that most severe congenital heart defects are discovered prior to discharge from hospital after birth. However, almost half are diagnosed outside of routine examinations, and in some cases the diagnosis is not made until after discharge. The results indicate a need for new studies and for a quality registry of congenital heart defects to further improve diagnosis and early treatment.

Intake of sucrose-sweetened soft beverages during pregnancy and risk of congenital heart defects (CHD) in offspring: a Norwegian pregnancy cohort study.

Studies report increased risk of congenital heart defects (CHD) in the offspring of mothers with diabetes, where high blood glucose levels might confer the risk. We explored the association between intake of sucrose-sweetened soft beverages during pregnancy and risk of CHD. Prospective cohort data with 88,514 pregnant women participating in the Norwegian Mother and Child Cohort Study was linked with information on infant CHD diagnoses from national health registers and the Cardiovascular Diseases in Norway Project. Risk ratios were estimated by fitting generalized linear models and generalized additive models. The prevalence of children with CHD was 12/1000 in this cohort (1049/88,514). Among these, 201 had severe and 848 had non-severe CHD (patent ductus arteriosus; valvular pulmonary stenosis; ventricular septal defect; atrial septal defect). Only non-severe CHD was associated with sucrose-sweetened soft beverages. The adjusted risk ratios (aRR) for non-severe CHD was 1.30 (95% CI 1.07-1.58) for women who consumed 25-70 ml/day and 1.27 (95% CI 1.06-1.52) for women who consumed ≥ 70 ml/day when compared to those drinking ≤ 25 ml/day. Dose-response analyses revealed an association between the risk of non-severe CHD and the increasing exposure to sucrose-sweetened soft beverages, especially for septal defects with aRR = 1.26 (95% CI 1.07-1.47) per tenfold increase in daily intake dose. The findings persisted after adjustment for maternal diabetes or after excluding mothers with diabetes (n = 19). Fruit juices, cordial beverages and artificial sweeteners showed no associations with CHD. The findings suggest that sucrose-sweetened soft beverages may affect the CHD risk in offspring.

Survey of 23 Nordic university hospitals showed that 77% lacked written procedures for measuring and interpreting blood pressure in infants.

AIM: This study determined the use of standardised procedures for infant noninvasive blood pressure (NIBP) measurements in the Nordic countries and aimed to identify factors included in the standardisation and interpretation of NIBP measurements in infants. METHODS: A cross-sectional electronic questionnaire survey was sent to 84 physicians in all 23 university hospitals in Sweden, Norway, Denmark, Finland and Iceland and was completed from February to March 2017. The survey contained respondent characteristics, the presence and description of standardised procedures for NIBP measurements, daily practice of NIBP measurements and methodological considerations and interpretation of NIBP measurements in a healthy six-month-old child. RESULTS: We received responses from 55 of 84 physicians working in all 23 Nordic university hospitals, in paediatric cardiology (n = 22), general paediatrics (n = 16), paediatric nephrology (n = 14) and other fields (n = 3). Less than a quarter (23%) said their hospital issued specific NIBP procedures relating to infants and they referred to 19 different sources of information. The factors that were most commonly assessed for interpretation were age (100%), arousal state (78%) and cuff size (76%). CONCLUSION: Most of the university hospital units treating children lacked age-specific written procedures for measuring and interpreting infant NIBP, and there is a strong need for common Nordic guidelines.

Fluid accumulation in the staged Fontan procedure: the impact of colloid osmotic pressures.

OBJECTIVES: Despite Fontan surgery showing improved results, fluid accumulation and oedema formation with pleural effusion are major challenges. Transcapillary fluid balance is dependent on hydrostatic and colloid osmotic pressure (COP) gradients; however, the COP values are not known for Fontan patients. The aim of this study was to evaluate the COP of plasma (COPp) and interstitial fluid (COPi) in children undergoing bidirectional cavopulmonary connection and total cavopulmonary connection. METHODS: This study was designed as a prospective, observational study. Thirty-nine children (age 3 months-4.9 years) undergoing either bidirectional cavopulmonary connection or total cavopulmonary connection procedures were included. Blood samples and interstitial fluid were obtained prior to, during and after the preoperative cardiac catheterization and surgery with the use of cardiopulmonary bypass (CPB). Interstitial fluid was harvested using the wick method when the patient was under general anaesthesia. Plasma and interstitial fluid were measured by a colloid osmometer. Baseline values were compared with data from healthy controls. RESULTS: Baseline COPp was 20.6 ± 2.8 and 22.0 ± 3.2 mmHg and COPi was 11.3 ± 2.6 and 12.5 ± 3.5 mmHg in the bidirectional cavopulmonary connection group and the total cavopulmonary connection group, respectively. These values were significantly lower than in healthy controls. The COPp was slightly reduced throughout both procedures and normalized after surgery. The COPi increased slightly during the use of CPB and significantly decreased after surgery, resulting in an increased COP gradient and was correlated to pleural effusion. CONCLUSIONS: Fluid accumulation seen after Fontan surgery is associated with changes in COPs, determinants for fluid filtration and lymphatic flow. CLINICALTRIALS.GOV IDENTIFIER: NCT 02306057: https://clinicaltrials.gov/ct2/results?cond=&term=NCT+02306057.