Endurance training may improve exercise capacity, lung function and quality of life in Fontan patients.

Children born with univentricular hearts undergo staged surgical procedures to a Fontan circulation. Long-term experience with Fontan palliation has shown dramatically improved survival but also of a life-long burden of an abnormal circulation with significant morbidity. Many Fontan patients have reduced exercise capacity, oxygen uptake, lung function and quality of life. Endurance training may improve submaximal, but not maximal, exercise capacity, lung function and quality of life. Physical activity and endurance training is also positively correlated with sleep quality. Reviewing the literature and from our single-centre experience, we believe there is enough evidence to support structured individualised endurance training in most young Fontan patients.

Fontan circulation has improved life expectancy for infants born with complex heart disease over the last 50 years but has also resulted in significant morbidity.

The prognosis for infants born with complex heart disease improved dramatically with the introduction of the Fontan circulation 50 years ago. With today's carefully designed and staged operations to a Fontan circulation, life expectancy has increased and most children will survive into adult life. The Fontan circulation entails an unphysiological circulation with high risk for multiple organ system dysfunction. Neurodevelopmental disabilities with adverse psychosocial effects are prevalent. The Fontan circulation may eventually fail and necessitate heart transplantation. CONCLUSION: Fifty years development of the Fontan circulation to today's staged surgical procedures has improved survival but also revealed the burden of a high morbidity for a growing number of patients.

Appropriate heart rate during exercise in Fontan patients.

OBJECTIVE: To evaluate heart rate against workload and oxygen consumption during exercise in Fontan patients. METHOD: Fontan patients (n = 27) and healthy controls (n = 25) underwent cardiopulmonary exercise testing with linear increase of load. Heart rate and oxygen uptake were measured during tests. Heart rate recovery was recorded for 10 minutes. RESULTS: Heart rate at midpoint (140 ± 14 versus 153 ± 11, p < 0.001) and at maximal effort (171 ± 14 versus 191 ± 10 beats per minute, p < 0.001) of test was lower for patients than controls. Heart rate recovery was similar between groups. Heart rate in relation to workload was higher for patients than controls both at midpoint and maximal effort. Heart rate in relation to oxygen uptake was similar between groups throughout test. Oxygen pulse, an indirect surrogate measure of stroke volume, was reduced at maximal effort in patients compared to controls (6.6 ± 1.1 versus 7.5 ± 1.4 ml·beat-1·m-2, p < 0.05) and increased significantly less from midpoint to maximal effort for patients than controls (p < 0.05). CONCLUSIONS: Heart rate is increased in relation to workload in Fontan patients compared with controls. At higher loads, Fontan patients seem to have reduced heart rate and smaller increase in oxygen pulse, which may be explained by inability to further increase stroke volume and cardiac output. Reduced ability to increase or maintain stroke volume at higher heart rates may be an important limiting factor for maximal cardiac output, oxygen uptake, and physical performance.

Snus users had high levels of nicotine, cotinine and 3-hydroxycotinine in their breastmilk, and the clearance was slower than in smoking mothers.

AIM: Using snus, an oral moist tobacco, has increased among pregnant women in Sweden, the only European Union country where sales are legal. This study evaluated whether snus generated similar concentrations of nicotine and its metabolites in breastmilk to cigarette smoking. METHODS: We analysed 49 breastmilk samples from 33 nursing mother - 13 snus users, six cigarette smokers and 14 controls - for concentrations of nicotine, cotinine and 3-hydroxycotinine. The mothers were recruited at antenatal clinics in Sweden from 2007 to 2012. RESULTS: The median nicotine concentration in breastmilk of the snus users was 38.7 ng/mL (0-137) versus 24.0 ng/mL (0-56) in smokers, with median cotinine levels of 327.6 ng/mL (37-958) versus 164.4 ng/mL and median 3-hydroxycotinine levels of 202.7 ng/mL (28-452) versus 112.4 (0-231), respectively. Nicotine was still detected in the breastmilk of eight of the 13 snus users after abstaining from tobacco for a median duration of 11 hours (0.6-12.5), while the breastmilk of the smokers was nicotine-free after four hours' abstinence. CONCLUSION: Snus users had high levels of nicotine and metabolites in their breastmilk and nicotine was found even after 12.5 hours of abstinence.

Physical exercise may improve sleep quality in children and adolescents with Fontan circulation.

OBJECTIVE: To study physical activity and sleep in Fontan patients and healthy controls before and after an endurance training program, and after 1 year. METHOD: Fontan patients (n = 30) and healthy controls (n = 25) wore accelerometers for seven consecutive days and nights during a school week before and after a 12-week endurance training program and after 1 year. RESULTS: Patients had similar sleep duration and sleep efficiency as healthy controls. Latency to sleep onset in minutes was longer for patients than controls (22.4 (4.3-55.3) minutes versus 14.8 (8.6-29.4) minutes, p < 0.01). More time in moderate-to-vigorous activity daytime was correlated with increased sleep time (p < 0.05; r2 = 0.20), improved sleep efficiency (p < 0.01; r2 = 0.24) and less time as wake after sleep onset (p < 0.05; r2 = 0.21) for patients but not controls. Sleep variables did not change after the exercise intervention for patients or controls. After 1 year, patients had decreased total sleep time, decreased sleep efficiency, increased accelerometer counts during sleep and more time as wake after sleep onset during sleep time, but not controls. CONCLUSIONS: Fontan patients have prolonged latency to sleep onset compared with controls. More time in physical activities was correlated with better sleep quality for the patients. Also, subjects with low sleep efficiency and long latency to sleep onset may benefit most from physical exercise. These patients should be encouraged to engage in individually designed physical exercise as this could improve sleep quality.

Impaired lung function in children and adolescents with Fontan circulation may improve after endurance training.

OBJECTIVES: The objective of this research was to study lung function, physical capacity, and effect of endurance training in children and adolescents after Fontan palliation compared with healthy matched controls. METHODS: Fontan patients (n=30) and healthy matched control patients (n=25) performed dynamic and static spirometry, and pulmonary diffusing capacity and maximal oxygen uptake tests, before and after a 12-week endurance training programme and at follow-up after 1 year. RESULTS: Fontan patients had a restrictive lung pattern, reduced pulmonary diffusing capacity (4.27±1.16 versus 6.61±1.88 mmol/kPa/minute, p<0.001), and a reduced maximal oxygen uptake (35.0±5.1 versus 43.7±8.4 ml/minute/kg, p<0.001) compared with controls. Patients had air trapping with a higher portion of residual volume of total lung capacity compared with controls (26±6 versus 22±5%, p<0.05). Vital capacity increased for patients, from 2.80±0.97 to 2.91±0.95 L, p<0.05, but not for controls after endurance training. The difference in diffusing capacity between patients and controls appeared to be greater with increasing age. CONCLUSIONS: Fontan patients have a restrictive lung pattern, reduced pulmonary diffusing capacity, and reduced maximal oxygen uptake compared with healthy controls. Endurance training may improve vital capacity in Fontan patients. The normal increase in pulmonary diffusing capacity with age and growth was reduced in Fontan patients, which is concerning. Apart from general health effects, exercise may improve lung function in young Fontan patients and should be encouraged.

Can endurance training improve physical capacity and quality of life in young Fontan patients?

OBJECTIVE: Children after Fontan palliation have reduced exercise capacity and quality of life. Our aim was to study whether endurance training could improve physical capacity and quality of life in Fontan patients. METHODS: Fontan patients (n=30) and healthy age- and gender-matched control subjects (n=25) performed a 6-minute walk test at submaximal capacity and a maximal cycle ergometer test. Quality of life was assessed with Pediatric Quality of Life Inventory Version 4.0 questionnaires for children and parents. All tests were repeated after a 12-week endurance training programme and after 1 year. RESULTS: Patients had decreased submaximal and maximal exercise capacity (maximal oxygen uptake 35.0±5.1 ml/minute per·kg versus 43.7±8.4 ml/minute·per·kg, p<0.001) and reported a lower quality of life score (70.9±9.9 versus 85.7±8.0, p<0.001) than controls. After training, patients improved their submaximal exercise capacity in a 6-minute walk test (from 590.7±65.5 m to 611.8±70.9 m, p<0.05) and reported a higher quality of life (p<0.01), but did not improve maximal exercise capacity. At follow-up, submaximal exercise capacity had increased further and improved quality of life was sustained. The controls improved their maximal exercise capacity (p<0.05), but not submaximal exercise capacity or quality of life after training. At follow-up, improvement of maximal exercise capacity was sustained. CONCLUSIONS: We believe that an individualised endurance training programme for Fontan patients improves submaximal exercise capacity and quality of life in Fontan patients and the effect on quality of life appears to be long-lasting.

Prenatal Exposure to Snus Alters Heart Rate Variability in the Infant.

INTRODUCTION: Maternal use of smoked tobacco during pregnancy causes significant morbidity and mortality in the human infant including alterations in autonomic control with increased risk of sudden infant death syndrome. We hypothesized that maternal snus (smokeless tobacco) use during pregnancy affects autonomic cardiac regulation in the infant, as measured by heart rate variability (HRV) and the low frequency and high frequency ratio (LF/HF ratio). METHODS: A prospective observational study of 56 infants of women who used snus (n = 23) or cigarettes (n = 13) during pregnancy versus tobacco- and nicotine-free controls (n = 19). The nicotine dose was estimated by questionnaires at 4 timepoints pre- and post-natally. The infants' urine cotinine concentration and HRV during 2 hours of sleep were studied 1-2 months after birth. RESULTS: LF/HF ratio was higher in snus (mean 3.31; 95% CI 2.78-3.83) and smoke (3.51;2.54-4.47) compared to controls (2.15; 1.76-2.54, p = .002). Early prenatal nicotine exposure "without" any further exposure increased the LF/HF ratio (3.19; 2.55-3.84, p = .02). Continuous prenatal nicotine exposure "without" postnatal exposure was also associated with a residual increase in LF/HF ratio (4.40; 3.38-5.42, p < .001). There was no difference between infants exposed to smokeless versus smoked tobacco, suggesting a common constituent (nicotine) altering autonomic cardiac regulation. CONCLUSION: Infants to mothers who used snus during pregnancy showed lower vagal activity with an increased LF/HF ratio compared to controls, and similar to infants of smokers. Even early prenatal exposure to snus has a lasting impact on autonomic cardiac regulation suggesting a fetal "re-programing" of the developing autonomic nervous system. IMPLICATIONS: The results indicate that smokeless tobacco (Swedish snus) affects the developing autonomic nervous system during gestation. Even if exposure is interrupted during the first or second trimester, effects in autonomic cardiac regulation are seen in the 1-2 month-old infant. This underlines the importance of abstaining from all types of tobacco use during the whole pregnancy. Our findings may also have more general relevance to other routes by which nicotine can be delivered to a fetus and newborn.

Reduced physical exercise and health-related quality of life after Fontan palliation.

AIM: A growing number of patients with Fontan circulation are reaching adulthood, and there is increasing concern about their physical performance and quality of life. This study compared self-reported exercise and measured activity with quality of life in patients after Fontan palliation and healthy controls. METHODS: Physical exercise during an average school week was reported by 30 Fontan circulation patients aged eight to 20 years, and 25 healthy controls, followed by accelerometer recordings over seven days. All subjects and their parents answered a questionnaire on quality of life. RESULTS: Patients reported spending less time exercising each week than the controls (114 ± 66 minutes vs. 228 ± 147 minutes, p < 0.001). However, the overall measured activity and moderate-to-vigorous activity was similar for patients and controls. Patients reported a lower quality of life score than the controls (70.9 ± 9.9 vs. 85.7 ± 8.0, p < 0.001). CONCLUSION: In spite of similar measured total activity, Fontan patients reported less time engaged in regular physical exercise than healthy controls and their quality of life was lower than the controls. We speculate that promoting structured regular physical exercise could improve the quality of life of Fontan patients.

Respiratory Tract Infection and Risk of Hospitalization in Children with Congenital Heart Defects During Season and Off-Season: A Swedish National Study.

Respiratory tract infections (RTI) are common among young children, and congenital heart defect (CHD) is a risk factor for severe illness and hospitalization. This study aims to assess the relative risk of hospitalization due to RTI in winter and summer seasons for different types of CHD. All children born in Sweden and under the age of two, in 2006-2011, were included. Heart defects were grouped according to type. Hospitalization rates for respiratory syncytial virus (RSV) infection and RTI in general were retrieved from the national inpatient registry. The relative risk of hospitalization was calculated by comparing each subgroup to other types of CHD and otherwise healthy children. The relative risk of hospitalization was increased for all CHD subgroups, and there was a greater increase in risk in summer for the most severe CHD. This included RSV infection, as well as RTI in general. The risk of hospitalization due to RTI is greater for CHD children. Prophylactic treatment with palivizumab, given to prevent severe RSV illness, is only recommended during winter. We argue that information to healthcare staff and parents should include how the risk of severe infectious respiratory tract illnesses, RSV and others, is present all year round for children with CHD.

Adolescents With Congenital Heart Disease and Their Parents: Needs Before Transfer to Adult Care.

BACKGROUND: Patients with congenital heart disease (CHD) are in need of lifelong healthcare. For adolescents with CHD, this transfer to adult-care clinic can be difficult. OBJECTIVE: The aim was to identify and describe the needs of adolescents with CHD and their parents during the transition before transfer to adult cardiologic healthcare. METHODS: This study has an exploratory design with a qualitative approach, where 13 adolescents with CHD and their parents (n = 12) were individually interviewed. The interviews were analyzed with content analysis. RESULTS: The analysis of the adolescents' interviews resulted in 3 categories: change of relationships, knowledge and information, and daily living. The theme that emerged depicting the meaning of the categories found was Safety and control, indicating needs of continuity, knowledge, and taking responsibility. Analysis of the parents' answers gave 2 categories: change of relationship and daily living. The theme that emerged was safety and trust, indicating needs of continuity and shifting responsibility. CONCLUSIONS: The transition must be carefully planned to ensure that adolescents can master new skills to manage the transfer to adult cardiologic healthcare. A structured program may facilitate and fulfill the needs of the adolescents and their parents, taking into consideration the aspects of trust, safety, and control. However, the content and performance of such a program must also be examined. We plan to undertake an extensive research project in the area, and this study will be a baseline for further research.

Evaluating national guidelines for the prophylactic treatment of respiratory syncytial virus in children with congenital heart disease.

AIM: This is the first study to evaluate compliance with the 2003 Swedish national guidelines for prophylactic treatment of respiratory syncytial virus (RSV) in children with congenital heart disease (CHD). We estimated the relative risk (RR) of children with CHD being hospitalised with a RSV infection, studied the extent to which RSV prophylactic treatment with palivizumab corresponded to the guidelines and determined the morbidity of children with CHD who developed RSV infection despite prophylaxis. METHODS: This national observational study comprised prospectively registered data on 219 children with CHD treated with palivizumab, medical records on RSV cases and information on hospitalisation rates of children with CHD and RSV infection. RESULTS: The calculated RR of children with CHD being hospitalised with RSV infection was 2.06 (95% CI 1.6-2.6; p < 0.0001) compared with children without CHD. Approximately half of the patients (49%) born before the RSV season and 25% born during the RSV season did not start treatment as recommended by the guidelines. CONCLUSION: Having CHD increased the rate and estimated RR of children being hospitalised with RSV infection. The guidelines were not followed for about half of the children born before a RSV season and a quarter of the children born during a RSV season and need updating.

Warfarin dose prediction in children using pharmacometric bridging--comparison with published pharmacogenetic dosing algorithms.

PURPOSE: Numerous studies have investigated causes of warfarin dose variability in adults, whereas studies in children are limited both in numbers and size. Mechanism-based population modelling provides an opportunity to condense and propagate prior knowledge from one population to another. The main objectives with this study were to evaluate the predictive performance of a theoretically bridged adult warfarin model in children, and to compare accuracy in dose prediction relative to published warfarin algorithms for children. METHOD: An adult population pharmacokinetic/pharmacodynamic (PK/PD) model for warfarin, with CYP2C9 and VKORC1 genotype, age and target international normalized ratio (INR) as dose predictors, was bridged to children using allometric scaling methods. Its predictive properties were evaluated in an external data set of children 0-18 years old, including comparison of dose prediction accuracy with three pharmacogenetics-based algorithms for children. RESULTS: Overall, the bridged model predicted INR response well in 64 warfarin-treated Swedish children (median age 4.3 years), but with a tendency to overpredict INR in children ≤2 years old. The bridged model predicted 20 of 49 children (41 %) within ± 20 % of actual maintenance dose (median age 7.2 years). In comparison, the published dosing algorithms predicted 33-41 % of the children within ±20 % of actual dose. Dose optimization with the bridged model based on up to three individual INR observations increased the proportion within ±20 % of actual dose to 70 %. CONCLUSION: A mechanism-based population model developed on adult data provides a promising first step towards more individualized warfarin therapy in children.

Nicotine in breast milk influences heart rate variability in the infant.

AIM: To study the effects of postnatal exposure to nicotine on the regulation of heart rate and blood pressure in infants. SUBJECTS AND METHODS: Thirty-eight mother-infant pairs were studied. Twenty nonsmoking and 18 smoking (2-20 cigarettes per day) mothers were included. All infants were healthy, exclusively breastfed and their postnatal age was 6 weeks. During a home visit infant's urine and mothers' milk were sampled and concentrations of nicotine and cotinine were analyzed. Infants' electrocardiogram (ECG) were recorded, sleep state documented and blood pressure during sleep was measured. Heart rate variability (HRV) was calculated with spectral analysis of R-R intervals. RESULTS: The smoking mothers exposed their infants to nicotine in milk with a median nicotine concentration of 47 (8-192) mug/L. Analysis of infants' urine showed that the nonsmoking group had 0.8 (0-5.2) and the smoke group 60 (17-139) mug cotinine/L (p < 0.01). The frequency domain low-to-high frequency (LF/HF) ratio, was correlated to milk nicotine concentrations in the milk sample, from smoking mothers. HRV decreased, with increasing milk nicotine, ingested by the boys (r =-0.74, p = 0.02) but not the girls (r =-0.13, p = 0.76). The differences of mean arterial pressure between sleep states in the infants, were significantly lower in the smoke group 5.8(6.8) compared to the nonsmoke group 11.5(7.2) mmHg (p = 0.03). CONCLUSIONS: Postnatal exposure to nicotine influences autonomic cardiovascular control in infants.

Long-term survival in children with atrioventricular septal defect and common atrioventricular valvar orifice in Sweden.

BACKGROUND: The survival for patients with atrioventricular septal defect has improved markedly over the last decades and, during the same period, the survival of children with Down's syndrome has also increased. The aim of our study was to investigate long-term survival in patients having atrioventricular septal defect with common valvar orifice, but without associated significant congenital heart defects, in the setting of Down's syndrome, comparing the findings to those in chromosomally normal children with the same malformation. METHODS AND RESULTS: In a population-based retrospective study, we scrutinised the medical records from 801 liveborn children with atrioventricular septal defect born in Sweden during the period 1973 through 1997. Data on gender, presence or absence of Down's syndrome, associated congenital heart defects, date of birth, operation and death were recorded and followed up until 2001. An isolated atrioventricular septal defect with common atrioventricular valvar orifice was present in 502 children, of whom 86% had Down's syndrome. We found a significant reduc tion over time in age at operation, and in postoperative mortality at 30 days, from 28 to 1%. Using a multiple logistic regression model, we found no significant differences in mortality between genders, nor between those with or without Down's syndrome. Early corrective surgery could not be identified as a significant independent factor for survival. The 5-year postoperative survival in patients with Down's syndrome increased from 65% over the period from 1973 through 1977, to about 90% in the period 1993 through 1997, and the same trend was observed in chromosomally normal patients. CONCLUSIONS: Survival in uncomplicated atrioventricular septal defect with common atrioventricular valvar orifice has greatly increased, and surgical correction is now equally successful in patients with Down's syndrome and chromosomally normal patients, and for both genders. Death in connection with surgery is no longer the major threat, and focus must now be on long-term follow-up.