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Aims: To explore the prevalence and incidence of paediatric implantable cardioverter-defibrillator (ICD) patients in Sweden and identify risk factors associated with appropriate shocks and adverse events.

Methods and results: We performed a nationwide, retrospective cohort study of ICD use in paediatric patients (<19 years) between 1995 and 2017; 120 patients underwent ICD implantation at median age 14.7 (range 1.1–18.9) years and were followed for 7.1 (0.3–20.4) years. Fifty-four patients (45%) received a primary preventive ICD; 46% had cardiomyopathy, and 41% had primary electrical disease. The estimated 5-year survival without appropriate shocks was 68% (confidence interval 59–78). Secondary preventive ICDs and lower weight (<30 kg) at implantation were associated with a higher rate of appropriate shocks, respectively. Lower weight at implantation was not a risk factor for adverse events. Inadequate medication and insufficient compliance were common in patients who experienced shocks. Less than half (46%) of the cases with inappropriate shocks were adequately medicated with good compliance. Secondly, an incidence and prevalence study of all paediatric and adult patients who had an ICD implanted in Sweden was analysed in 4-year periods between 2002 and 2021. The incidence of paediatric ICD implantations in Sweden peaked at 0.56 per 100 000 person-years in 2010–13, decreasing to 0.45 per 100 000 person-years in the last study period (2018–21).

Conclusion: Appropriate shocks were more than twice as common in the youngest patient group, whereas adverse events were not more frequent than in the older patient group. Inadequate medication and lack of compliance were common in connection with ICD shocks.

Objective: To characterize patients with protein-losing enteropathy (PLE) diagnosed before age 18 years within a nationwide Swedish Fontan cohort.

Methods: Surgical records and medical charts were reviewed for all patients born after January 1, 1993, who underwent Fontan completion before January 1, 2021.

Results: Among 573 reviewed patients, 28 (4.8%) developed PLE. The median time to onset of PLE after Fontan was 1.5 years (interquartile range, 0.5-5.5 years). Right ventricular morphology was associated with PLE (odds ratio, 2.3; 95% confidence interval, 1.04-5.0). Twenty-three patients (82%) received PLE-directed therapies, including pulmonary vasodilators (n = 17; 61%), subcutaneous heparin (n = 14; 50%), and/or long-term corticosteroids (n = 13; 46%). Eleven patients (39%) underwent a total of 18 catheter interventions, including 1 fenestration and 1 lymphatic intervention. Three pacemaker procedures were performed after a PLE diagnosis. Eight patients underwent heart transplant (26%). Patients with an early onset of PLE (<2 years from Fontan completion) frequently had a history of pulmonary venous congestion. Five-year overall survival was 88%, and 5-year transplant-free survival was 79%.

Conclusions: PLE remains a serious complication following Fontan, with notable mortality. Patients with right ventricular morphology of the systemic ventricle had a higher risk of PLE. Previous pulmonary venous congestion was common when PLE was diagnosed early after Fontan. Catheter-based interventions were frequently used to optimize hemodynamics; lymphatic interventions are likely to become more common. In therapy-refractory patients, heart transplantation remains an option.

As cold-water immersion becomes more popular and accessible, it is important to explore potential risks. This study examines the cardiac autonomic response and arrhythmia occurrence in healthy adolescents during face and body immersion. Healthy ninth-grade students, aged 15–16 years, were recruited to perform face immersion (FI) in 10°C water and body immersion in 2°C water (IWI). Electrocardiograms (ECGs) were continuously recorded, and the heart rate (HR) response and occurrence of arrhythmias were assessed. Among the 54 individuals performing FI, six had supraventricular extrasystoles, and two had ventricular bigeminy. Among the 20 performing IWI, four had supraventricular extrasystoles. The HR response was more pronounced during FI compared to IWI (p < 0.001). During both FI and IWI, girls showed initially higher HR and more pronounced HR reduction than boys, but there were no significant sex differences (p = 0.26). During the first 30 seconds of IWI, boys maintained a steady HR (p = 0.176), while girls experienced a near-linear reduction (p = 0.009). This study indicates a low risk of severe arrhythmias when briefly immersing the body in ice-cold water in healthy adolescents. However, the risk could increase if combined with face submersion and apnea.

Aims: Cardiomyopathies are a heterogeneous group of genetic disorders requiring specialised, multidisciplinary management to optimize patient outcomes. A critical aspect of care is the transition of paediatric patients to adult services, which varies significantly across healthcare systems.

This study assessed current practices in care transition and multidisciplinary management of inherited and rare cardiomyopathies across specialised European centres within the European Reference Network for rare and low prevalence complex diseases of the heart network.

Methods and results: A 21-question survey was distributed to healthcare providers within the network. A single participant (i.e. cardiologist with expertise in the diagnosis and management of inherited and rare cardiomyopathies) from each centre was approached. Responses from 26 centres across 12 European countries were analysed using descriptive statistics to evaluate institutional characteristics, transition protocols, and multidisciplinary team involvement. While 81% of centres reported having a transition plan, only 42% implemented it for all patients, and 19% had no formal protocol. Multidisciplinary care was well integrated, with regular team discussions, though key professionals such as psychologists and nurses were often absent. The lack of structured transition programmes, inconsistent use of standardized protocols, and a shortage of specialists in cardiogenetics emerged as major unmet needs.

Conclusion: Significant variability exists in the transition and multidisciplinary care of patients with inherited and rare cardiomyopathies. Standardized transition protocols, greater involvement of multiple healthcare professionals, and enhanced training in cardiogenetics are needed to ensure continuity of care and improve patient care across Europe.

Objectives: This study aimed to retrospectively assess cardiac autonomic activity in children with LQTS, considering genotype, symptoms, sex, age, and beta-blocker therapy (BB) and compare it to healthy controls.

Methods: Heart rate variability (HRV), using power spectrum analysis, was analyzed in 575 Holter recordings from 116 children with LQTS and in 69 healthy children. The data were categorized into four age-groups and four heart rate (HR) ranges.

Results: In LQT1 and LQT2, increasing HR corresponded to significantly lower low (LF) and high frequency (HF) compared to controls. Total power (PTOT) was lower in all LQT1 age-groups compared to controls at HR 120–140 bpm (1–15 years: p <.01; 15–18 years: p =.03). At HR 80–100, LQT1 patients aged 1–10 years had lower HF than LQT2 patients (1–5 years: p =.05; 5–10 years: p =.02), and LQT2 patients aged 15–18 years had lower HF than LQT1 patients (p <.01). Symptomatic patients aged 10–15 years had lower PTOT at HR 100–120 bpm than asymptomatic patients (p =.04). LQT1 girls aged 10–15 and 15–18 years had a lower PTOT (10–15 years: p =.04; 15–18 years: p =.02) than boys.

Conclusion: This study shows a correlation between HR and changes in HRV parameters. At higher HRs, LQTS patients generally had lower HRV values than controls, suggesting an abnormal autonomic response. These results may strengthen the link between physical activity and arrhythmias in LQTS.

Objectives: Previous reports indicate bone deficits in patients with Fontan circulation. However, the consequences of these deficits on bone strength and when these changes occur are unclear.

Aim: To compare the tibial bone strength-strain index between young patients (6-19 years) with Fontan circulation and age- and sex-matched controls, and to determine strength-strain-index in subgroups of children (6-12 years) and adolescents (13-19 years) versus controls.

Method: The tibia was examined with peripheral quantitative CT. Based on the assessed data, bone strength-strain index was calculated in the lateral and anterior-posterior directions.

Results: Twenty patients with Fontan and twenty controls (mean age 13.0 ± 4.4 years; 50% females) were examined. Patients had a lower strength-strain index in the lateral direction compared to controls (808.4 ± 416.8mm³ versus 1162.5 ± 552.1mm³, p = 0.043). Subgroup analyses showed no differences regarding strength-strain index in children (6-12 years) with Fontan circulation compared to controls. However, the adolescents (13-19 years) with Fontan circulation had lower strength-strain indexes in both the lateral and anterior-posterior directions compared to controls (1041.4 ± 299.8mm³ versus 1596.4 ± 239.6mm³, p < 0.001, and 771.7 ± 192.4mm³ versus 1084.9 ± 215.0mm³, p = 0.004). When adjusted for height, there were differences between patients (6-19 years) and controls in strength-strain indexes in both the lateral and anterior-posterior directions. In subgroup analyses, the results remained robust.

Conclusion: Young patients (6-19 years) with Fontan circulation have a lower strength-strain index in the tibia compared to controls. Subgroup analyses show that this deficit is mainly driven by the differences in adolescents (13-19 years), which might suggest that bone strength decreases with age.

BACKGROUND: Swimming is a genotype-specific trigger in long QT syndrome type 1 (LQT1).

OBJECTIVE: To examine the autonomic response to water activities in children and adolescents with LQT1.

METHODS: In this cross-sectional study, LQT1 patients were age and sex matched to one healthy control subject. Electrocardiograms (ECGs) were recorded during face immersion (FI), swimming, diving, and whole-body submersion (WBS). Heart rate (HR) and heart rate variability (HRV) was measured. The high frequency (HF) component of HRV was interpreted to reflect parasympathetic activity, while the low frequency (LF) component was interpreted as reflecting the combined influence of sympathetic and parasympathetic activity on autonomic nervous modulation of the heart.

RESULTS: Fifteen LQT1 patients (aged 7-19 years, all on beta-blocker therapy) and fifteen age and sex matched non-medicated controls were included. No significant ventricular arrhythmias were observed in the LQT1 population during the water activities. Out of these 15 matched pairs, 12 pairs managed to complete FI and WBS for more than 10 seconds and were subsequently included in HR and HRV analyses. In response to FI, the LQT1 group experienced a drop in HR of 48 bpm, compared to 67 bpm in the control group (p = 0.006). In response to WBS, HR decreased by 48 bpm in the LQT1 group and 70 bpm in the control group (p = 0.007). A significantly lower PTOT (p < 0.001) and HF (p = 0.011) component was observed before, during and after FI in LQT1 patients compared with the controls. Before, during and after WBS, a significantly lower total power (p < 0.001), LF (p = 0.002) and HF (p = 0.006) component was observed in the LQT1 patients.

CONCLUSION: A significantly lower HR decrease in response to water activities was observed in LQT1 subjects on beta-blocker therapy, compared to matched non-medicated controls. The data suggests an impaired parasympathetic response in LQT1 children and adolescents. An aberrant autonomic nervous system (ANS) response may cause an autonomic imbalance in this patient group.

Purpose: Adolescents with congenital heart disease transition from childhood to adulthood and transfer from pediatric-oriented to adult-oriented care. High-level empirical evidence on the effectiveness of transitional care is scarce. This study investigated the empowering effect (primary outcome) of a structured person-centered transition program for adolescents with congenital heart disease and studied its effectiveness on transition readiness, patient-reported health, quality of life, health behaviors, disease-related knowledge, and parental outcomes e.g., parental uncertainty, readiness for transition as perceived by the parents (secondary outcomes).

Methods: The STEPSTONES-trial comprised a hybrid experimental design whereby a randomized controlled trial was embedded in a longitudinal observational study. The trial was conducted in seven centers in Sweden. Two centers were allocated to the randomized controlled trial-arm, randomizing participants to intervention or control group. The other five centers were intervention-naïve centers and served as contamination check control group. Outcomes were measured at the age of 16 years (baseline), 17 years, and 18.5 years.

Results: The change in empowerment from 16 years to 18.5 years differed significantly between the intervention group and control group (mean difference = 3.44; 95% confidence interval = 0.27–6.65; p = .036) in favor of intervention group. For the secondary outcomes, significant differences in change over time were found in parental involvement (p = .008), disease-related knowledge (p = .0002), and satisfaction with physical appearance (p = .039). No differences in primary or secondary outcomes were detected between the control group and contamination check control group, indicating that there was no contamination in the control group.

Discussion: The STEPSTONES transition program was effective in increasing patient empowerment, reducing parental involvement, improving satisfaction with physical appearance, and increasing disease-related knowledge.

AIMS: In long QT syndrome (LQTS), primary prevention improves outcome; thus, early identification is key. The most common LQTS phenotype is a foetal heart rate (FHR) < 3rd percentile for gestational age (GA) but the effects of cohort, genotype, variant, and maternal β-blocker therapy on FHR are unknown. We assessed the influence of these factors on FHR in pregnancies with familial LQTS and developed a FHR/GA threshold for LQTS.

METHODS AND RESULTS: In an international cohort of pregnancies in which one parent had LQTS, LQTS genotype, familial variant, and maternal β-blocker effects on FHR were assessed. We developed a testing algorithm for LQTS using FHR and GA as continuous predictors. Data included 1966 FHRs at 7-42 weeks' GA from 267 pregnancies/164 LQTS families [220 LQTS type 1 (LQT1), 35 LQTS type 2 (LQT2), and 12 LQTS type 3 (LQT3)]. The FHRs were significantly lower in LQT1 and LQT2 but not LQT3 or LQTS negative. The LQT1 variants with non-nonsense and severe function loss (current density or β-adrenergic response) had lower FHR. Maternal β-blockers potentiated bradycardia in LQT1 and LQT2 but did not affect FHR in LQTS negative. A FHR/GA threshold predicted LQT1 and LQT2 with 74.9% accuracy, 71% sensitivity, and 81% specificity.

CONCLUSION: Genotype, LQT1 variant, and maternal β-blocker therapy affect FHR. A predictive threshold of FHR/GA significantly improves the accuracy, sensitivity, and specificity for LQT1 and LQT2, above the infant's a priori 50% probability. We speculate this model may be useful in screening for LQTS in perinatal subjects without a known LQTS family history.

Congenital long QT syndrome (LQTS) carries an increased risk for syncope and sudden death. QT prolongation promotes ventricular extrasystoles, which, in the presence of an arrhythmia substrate, might trigger ventricular tachycardia degenerating into fibrillation. Increased electrical heterogeneity (dispersion) is the suggested arrhythmia substrate in LQTS. In the most common subtype LQT1, physical exercise predisposes for arrhythmia and spatiotemporal dispersion was therefore studied in this context. Thirty-seven patients (57% on β-blockers) and 37 healthy controls (mean age, 31 vs. 35; range, 6-68 vs. 6-72 yr) performed an exercise test. Frank vectorcardiography was used to assess spatiotemporal dispersion as Tampl, Tarea, the ventricular gradient (VG), and the Tpeak-end interval from 10-s signal averages before and 7 ± 2 min after exercise; during exercise too much signal disturbance excluded analysis. Baseline and maximum heart rates as well as estimated exercise intensity were similar, but heart rate recovery was slower in patients. At baseline, QT and heart rate-corrected QT (QTcB) were significantly longer in patients (as expected), whereas dispersion parameters were numerically larger in controls. After exercise, QTpeakcB and Tpeak-endcB increased significantly more in patients (18 ± 23 vs. 7 ± 10 ms and 12 ± 17 vs. 2 ± 6 ms; P < 0.001 and P < 0.01). There was, however, no difference in the change in Tampl, Tarea, and VG between groups. In conclusion, although temporal dispersion of repolarization increased significantly more after exercise in patients with LQT1, there were no signs of exercise-induced increase in global dispersion of action potential duration and morphology. The arrhythmia substrate/mechanism in LQT1 warrants further study.

NEW & NOTEWORTHY: Physical activity increases the risk for life-threatening arrhythmias in LQTS type 1 (LQT1). The arrhythmia substrate is presumably altered electrical heterogeneity (a.k.a. dispersion). Spatiotemporal dispersion parameters were therefore compared before and after exercise in patients versus healthy controls using Frank vectorcardiography, a novelty. Physical exercise prolonged the time between the earliest and latest complete repolarization in patients versus controls, but did not increase parameters reflecting global dispersion of action potential duration and morphology, another novelty.