Cardiac problems in Down syndrome

Performance and Pacing Profiles of Competitive Track Events for Elite Athletes With Intellectual Impairment With and Without Additional Significant Impairments

PURPOSE

To compare the pacing profiles of elite track athletes with intellectual impairments (II) and those with Down syndrome (DS) in 400- and 1,500-m track events.

METHODS

The pacing data of 67 elite runners participating in the final 400-m (both genders) and 1,500-m (only males) track events of the Global Games (2023) were analyzed. Runners competed in two classes: a class for runners with II (without DS) and a separate class for runners with DS.

RESULTS

For the 400-m event, male and female runners in both classes decelerated from the first segment (0-200 m) to the second segment (200-400 m) as the time main effect was significant (p < .001); however, the pacing strategy for both genders differed between the II and DS class as reported by the significant Gender × Class interaction effect (p < .001). The running velocity over the two segments of the race decreased more significantly for the II runners without DS. There was also a significant interaction effect for the 1,500-m race (p < .001). The DS runners show a more significant drop in running velocity over the split times of the race and with more varied fluctuations compared with the II runners without DS.

CONCLUSION

This study highlights the significant differences in pacing between 400- and 1,500-m elite runners with II and with and without DS. Elite runners with DS run at an overall slower velocity and follow a significantly different pacing pattern compared with runners with II without DS. Our findings show that runners with DS are less able to regulate their exercise intensity over the race than runners with II without DS.

Heart Rate Variability in Individuals with Down Syndrome: A Scoping Review with Methodological Considerations

Individuals with Down syndrome (DS) present similar heart rate variability (HRV) parameters at rest but different responses to selected movement maneuvers in comparison to individuals without DS, which indicates reduced vagal regulation. The present study undertakes a scoping review of research on HRV in individuals with DS, with special attention paid to the compliance of the studies with standards and methodological paper guidelines for HRV assessment and interpretation. A review was performed using PubMed, Web of Science and CINAHL databases to search for English language publications from 1996 to 2020 with the MESH terms "heart rate variability" and "down syndrome", with the additional inclusion criteria of including only human participants and empirical investigations. From 74 studies, 15 were included in the review. None of the reviewed studies met the recommendations laid out by the standards and guidelines for providing the acquisition of RR intervals and necessary details on HRV analysis. Since authors publishing papers on this research topic do not adhere to the prescribed standards and guidelines when constructing the methodology, results of the research papers on the topic are not directly comparable. Authors need to design the study methodology more robustly by following the aforementioned standards, guidelines and recommendations.

Surgical palliation of univentricular heart disease in children with Down's syndrome: A systematic review

Objectives

No standard protocol is available for the management of children with Down's syndrome (DS) and a functional single ventricle. This review attempts to determine the outcomes of the single ventricular surgical palliation pathway in high-risk children with DS.

Methods

Several databases were searched using the following MeSH terms: ‘Congenital heart disease’, ‘Atrioventricular septal defect’, ‘Balanced AVSD’, ‘Unbalanced AVSD’, ‘Down's syndrome’, ‘Univentricular repair’, ‘bidirectional Glenn procedure’, and ‘Fontan procedure’. A structured algorithm was used for the selection of studies for an in-depth analysis.

Results

There was no universal agreement on the best surgical approach for unbalanced atrioventricular septal defect in DS. The majority of paediatric cardiac surgeons did not recommend the complete Fontan procedure; conversely, the use of a Glenn shunt (superior cavopulmonary connection) was preferred.

Conclusions

Careful assessment of the suitability for Fontan surgery, including the absence of elevated pulmonary vascular resistance, pulmonary arterial anatomy, and function of the dominant ventricle, is mandatory. A staged surgical procedure ending with complete Fontan repair provides acceptable medium-term results.

The electrocardiogram in Down syndrome

Down syndrome is the most common chromosomal abnormality, with an incidence of one case in every 650 live births. It is strongly associated with heart disease, which constitutes the main cause of mortality during the first 2 years of life in this population. Most of the cardiac abnormalities in patients with Down syndrome can be suspected by analysing the surface 12-lead ECG. The purpose of this systematic review was to analyse all available published material on surface ECG and cardiac rhythm and conduction abnormalities in patients with Down syndrome to facilitate the search to the clinical cardiologist and paediatrician.

Increased P-wave and QT dispersions necessitate long-term follow-up evaluation of Down syndrome patients with congenitally normal hearts

Reports state that Down syndrome (DS) patients with congenitally normal hearts might experience the development of cardiac abnormalities such as cardiac autonomic dysfunction, valvular lesions, bradycardia, and atrioventricular block. However, the presence of any difference in terms of P-wave dispersion (PWd) and QT dispersion (QTd) was not evaluated previously. This study prospectively investigated 100 DS patients with structurally normal hearts and 100 age- and sex-matched healthy control subjects. Standard 12-lead electrocardiograms were used to assess and compare P-wave and QT durations together with PWd and QTd. The median age of the DS patients and control subjects was 48 months. Heart rates and P-wave and QT dispersions were significantly greater in the DS group than in the control group (113 ± 22.9 vs 98.8 ± 16.6 bpm, p < 0.001; 31.3 ± 9.5 vs 24 ± 8.6 ms, p < 0.001; and 46.6 ± 15.9 vs 26 ± 9.1 ms, p < 0.001, respectively). A positive correlation was found between PWd and age in the DS patients (p < 0.05; r = 0.2). All children with DS should be followed up carefully with electrocardiography in terms of increased P-wave and QT dispersions even in the absence of concomitant congenital heart disease for management of susceptibility to arryhthmias.

Early postoperative outcomes following surgical repair of complete atrioventricular septal defects: is down syndrome a risk factor?

OBJECTIVE

To evaluate the impact of Down syndrome on the early postoperative outcomes of children undergoing complete atrioventricular septal defect repair.

DESIGN

Retrospective cohort study.

SETTING

Single tertiary pediatric cardiac center.

PATIENTS

All children admitted to PICU following biventricular surgical repair of complete atrioventricular septal defect from January 2004 to December 2009.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 107 children, 67 with Down syndrome, were included. Children with Down syndrome were operated earlier: 4 months (interquartile range, 3.5-6.6) versus 5.7 months (3-8.4) for Down syndrome and non-Down syndrome groups, respectively (p < 0.01). There was no early postoperative mortality. There was no significant difference in the prevalence of dysplastic atrioventricular valve between the two groups. Two children (2.9%) from Down syndrome and three children (7.5%) from non-Down syndrome group required early reoperation (p = 0.3). Junctional ectopic tachycardia was the most common arrhythmia, and the prevalence of junctional ectopic tachycardia was similar between the two groups (9% and 10% in Down syndrome and non-Down syndrome, respectively, p = 1). One patient from each group required insertion of permanent pacemaker for complete heart block. Children with Down syndrome had significantly higher prevalence of noncardiac complications, that is, pneumothorax, pleural effusions, and infections (p < 0.01), than children without Down syndrome. There was a trend for longer duration of mechanical ventilation in children with Down syndrome (41 hr [20-61 hr] vs 27.5 hr [15-62 hr], p = 0.2). However, there was no difference in duration of PICU stay between the two groups (2 d [1.3-3 d] vs 2 d [1-3 d], p = 0.9, respectively).

CONCLUSIONS

In our study, we found no difference in the prevalence of atrioventricular valve dysplasia between children with and without Down syndrome undergoing complete atrioventricular septal defect repair. This finding contrasts with previously published data, and further confirmatory studies are required. Although clinical outcomes were similar, children with Down syndrome had a significantly higher prevalence of noncardiac complications in the early postoperative period than children without Down syndrome.

Echocardiography in children with Down syndrome

Congenital heart disease is a common problem in children with Down syndrome (DS). Echocardiography plays an important role in the detection of both structural and functional abnormalities in this group of patients. Fetal echocardiography can help in the early recognition of DS by detecting soft markers of DS, but its main role is to define the exact nature of the suspected cardiac problem in the fetus. Postnatal echocardiography is mandatory in the first month of life for all neonates with DS. It is also indicated before any cardiac surgery and for serial follow-up after cardiac surgery. In this article, we discuss the types and mechanism of cardiac abnormalities in DS children and the role of both fetal and postnatal echocardiography in the detection of these abnormalities.

The App-Runx1 region is critical for birth defects and electrocardiographic dysfunctions observed in a Down syndrome mouse model

Down syndrome (DS) leads to complex phenotypes and is the main genetic cause of birth defects and heart diseases. The Ts65Dn DS mouse model is trisomic for the distal part of mouse chromosome 16 and displays similar features with post-natal lethality and cardiovascular defects. In order to better understand these defects, we defined electrocardiogram (ECG) with a precordial set-up, and we found conduction defects and modifications in wave shape, amplitudes, and durations in Ts65Dn mice. By using a genetic approach consisting of crossing Ts65Dn mice with Ms5Yah mice monosomic for the App-Runx1 genetic interval, we showed that the Ts65Dn viability and ECG were improved by this reduction of gene copy number. Whole-genome expression studies confirmed gene dosage effect in Ts65Dn, Ms5Yah, and Ts65Dn/Ms5Yah hearts and showed an overall perturbation of pathways connected to post-natal lethality (Coq7, Dyrk1a, F5, Gabpa, Hmgn1, Pde10a, Morc3, Slc5a3, and Vwf) and heart function (Tfb1m, Adam19, Slc8a1/Ncx1, and Rcan1). In addition cardiac connexins (Cx40, Cx43) and sodium channel sub-units (Scn5a, Scn1b, Scn10a) were found down-regulated in Ts65Dn atria with additional down-regulation of Cx40 in Ts65Dn ventricles and were likely contributing to conduction defects. All these data pinpoint new cardiac phenotypes in the Ts65Dn, mimicking aspects of human DS features and pathways altered in the mouse model. In addition they highlight the role of the App-Runx1 interval, including Sod1 and Tiam1, in the induction of post-natal lethality and of the cardiac conduction defects in Ts65Dn. These results might lead to new therapeutic strategies to improve the care of DS people.