Adults with Down syndrome have reduced cardiac response after light exercise testing

Physiological Mechanisms That Impact Exercise Adaptations for Individuals With Down Syndrome

ABSTRACT

Post, EM, and Kraemer, WJ. Physiological mechanisms that impact exercise adaptations for individuals with Down syndrome. J Strength Cond Res 37(12): e646-e655, 2023-Down syndrome (DS) is the most common chromosomal disorder diagnosed in the United States since 2014. There is a wide range of intellectual severities, with the average IQ of individuals with DS at approximately 50 and adults without intellectual delay at approximately 70-130. Individuals with DS vary from mild to severe cognitive impairment, depending on the phenotypic penetration on the 21st chromosome, with the average cognitive capacity equivalent to a cognitive functioning of an 8- to 9-year-old child. To have successful health, all aspects of health must be considered (i.e., overall health, fitness, and social). Both aerobic training and resistance training (RT) are favored for a healthy lifestyle. Resistance training specifically can help improve motor function and overall activities of daily living. Although many motivational and environmental barriers for individuals with DS can make exercising difficult, there are many ways to overcome those barriers (both intrinsically and extrinsically). Individuals with DS should strive for 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic exercise a week or a combination of both. The individual should also strive for 2 or more days a week of strengthening activities, such as RT, involving all muscle groups. These activities will help improve many aspects of life, leading to a better quality of life. Regular group exercise activity can help increase self-confidence and success socially in life. This review will focus on the underlying biological mechanisms related to DS, their influence on exercise, and the roles exercise plays in mediating positive health, physical fitness, and social lifestyle outcomes.

Early cardiac dysfunction in obese adolescents with Down syndrome or autism

BACKGROUND

Obesity in adolescents with intellectual and developmental disabilities) occurs at twice the frequency as their typically developing peers. Typically developing adolescents with obesity have abnormal cardiac function (as measured by strain echocardiography) and cardiac mass, but the effects of obesity on cardiac health in adolescents with Down syndrome or autism spectrum disorder are unknown. The purpose of this study was to evaluate the impact of body mass index on cardiac function in adolescents with Down syndrome or autism.

METHODS

Adolescents (age 12-21 years) with Down syndrome (n = 28), autism (n = 33), and age-/sex-matched typically developing controls (n = 15) received an echocardiogram optimised for strain analysis at a single timepoint. Measures of ventricular function, mass, and size were collected. Regression modelling evaluated the impact of body mass index and intellectual and developmental disabilities diagnosis on these cardiac measures.

RESULTS

In regression modelling, an elevated body mass index z-score was associated with diminished systolic biventricular function by global strain (left ventricular longitudinal strain β 0.87, P < 0.001; left ventricular circumferential strain β 0.57, p 0.003; right ventricular longitudinal strain β 0.63, P < 0.001). Diminished left ventricular diastolic function by early diastolic strain rate was also associated with elevated body mass index (global longitudinal end-diastolic strain rate β -0.7, P < 0.001). No association was found between traditional (non-strain) measures of systolic and diastolic ventricular function and body mass index z-score.

CONCLUSIONS

Obesity in adolescents with Down syndrome or autism negatively impacts cardiac function as measured by echocardiographic strain analysis that was not detected by traditional parameters.

Down syndrome patients with normal hearts: are they really normal?

Even though congenital heart disease is a common finding in down syndrome (DS) patients, some of them have anatomically normal hearts. However, the term "normal" might not be suitable, as these patients usually suffer from functional cardiac dysfunction. Several research highlighted that despite the absence of anatomical heart defects, subtle cardiac function derangements are present in DS patients. We aim to assess cardiac functions by Two-dimensional echocardiography and tissue Doppler imaging (TDI) in pediatric DS patients who have anatomically normal hearts. One hundred seventy-two patients with karyotyping confirmed DS with anatomically normal hearts and 165 healthy normal control children were enrolled in the current study. Their cardiac functions were assessed using both 2-dimensional echocardiography and TDI. Both patients and controls had structurally and anatomically normal hearts. In DS patients, the right side of the heart showed a significant reduction in both systolic and diastolic functions. Systolic dysfunction was evident by significantly decreased levels of Tricuspid annular plane systolic excursion and systolic wave by TDI. Diastolic dysfunction of the right ventricle was evident by prolonged deceleration time by conventional echocardiography and a significant decrease in annular tissue doppler velocity during early diastole/late diastole ratio by TDI. The E/De ratio was significantly increased. Even with anatomically normal hearts, DS patients should undergo cardiac function assessment by echocardiography & TDI. TDI is superior to conventional echocardiography in detecting subtle cardiac dysfunction especially left ventricular diastolic dysfunction in DS patients. TDI showed a significant decrease in the early/atrial ratio of mitral valve annulus and prolongation of left ventricle isometric relaxation time in DS children. Also, the left ventricle E/De ratio was prolonged denoting elevated filling pressures and diastolic dysfunction. This indicates that the TDI has higher sensitivity to detect diastolic dysfunction than conventional Echocardiography. Biventricular TDI-derived myocardial performance index was found to be significantly increased in DS children.

Comprehensive cardiopulmonary profile of individuals with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) have low levels of cardiorespiratory fitness and previous studies have shown that these low levels of fitness have a physiological cause. During exercise, the cardiovascular, ventilatory and muscular systems are simultaneously active. While individual parameters of these systems have been investigated in DS before, the interaction between these parameters and systems have not been discussed in detail. Doing so may provide important insight regarding the aetiology of low cardiorespiratory fitness and which parameters of the cardiovascular, pulmonary and muscular systems are altered in individuals with DS compared with their peers without DS.

METHODS

Cardiopulmonary exercise tests were performed in healthy adults with and without DS. Parameters related to the cardiovascular, ventilatory and muscular systems were collected until VO_2peak . In total, 51 participants were included in analysis, of which 21 had DS.

RESULTS

Individuals with DS showed lower peak values for all collected outcomes (P ≤ 0.001) compared with those without DS, except for ventilatory threshold as a percentage of maximal oxygen uptake and V_E /VCO₂ slope, which were similar.

CONCLUSIONS

Our results show that individuals with DS present impairments across the cardiovascular, ventilatory and muscular aspects of the cardiopulmonary system.

Cardiac Structure and Function in Adults with Down Syndrome

Various factors may alter the risk for cardiovascular disease in adults with Down syndrome (Ds), yet few studies have examined differences in cardiac physiology in this population. Previous research suggested lower systolic and diastolic function, but inconsistent methodologies and younger samples warrant research in adults with Ds. Our aim is to compare the cardiac structure and function of adults with Ds to age- and sex-matched adults without Ds. Echocardiography was used to assess systolic function, diastolic function, and cardiac structure in n = 19 adults (Ds n = 9, control n = 10). Regarding cardiac structure, adults with Ds had increased left ventricular posterior wall thickness at end-systole compared to adults without Ds (p = 0.007). Regarding systolic and diastolic function, adults with Ds were found to have lower septal peak systolic annular velocity (S') (p = 0.026), lower lateral and septal mitral annular early diastolic velocity (E') (p = 0.007 and p = 0.025, respectively), lower lateral peak mitral annular late diastolic velocity (A') (p = 0.027), and higher lateral and septal mitral annular early systolic velocity to diastolic velocity ratios (E/e') (p = 0.001 and p = 0.001, respectively). Differences in both cardiac structure and function were found when comparing adults with Ds to matched adults without Ds. Most of the differences were indicative of worse diastolic function.

Hemodynamic and cardiorespiratory responses to submaximal and maximal exercise in adults with Down syndrome

Introduction: The genetic disorder causing Down syndrome (DS) affects the cardiorespiratory and hemodynamic parameters. When exercising, sufficient blood flow is necessary for active muscles. Cardiac output (Q) must be proportional to the peripheral requirements. In case the stroke volume (SV) is lower, the heart rate (HR) will increase further in order to maintain an adequate blood flow in the active territories (HR compensatory response). People with DS have a lower HR response to maximal exercise. Nevertheless, the response of the hemodynamic and cardiorespiratory parameters during the submaximal phases of maximal exercise was not well studied.

Objective: to evaluate cardiorespiratory and hemodynamic parameters 1) during submaximal and 2) maximal metabolic treadmill test in individuals with and without DS.

Methods: fifteen adults with DS (age = 27.33 ± 4.98 years old; n = 12 males/3 females) and 15 adults without disabilities, matched by age and sex, participated in this cross-sectional study. Peak and submaximal cardiorespiratory and hemodynamic parameters were measured during a treadmill test. Linear mixed-effects models were used to analyse interactions between the variables. Post-hoc analyses were employed to assess within and between-group differences.

Results: The DS group showed lower peak values for ventilation (VE), respiratory exchange ratio (RER), tidal volume (VT), ventilatory equivalent for O2 (VEqO2), end-tidal partial pressure for O2 (PETO2), O2 uptake (VO2) and CO2 production (all p &lt; 0 .050), Q, SV, systolic and diastolic blood pressure (SBP, DBP), and HR (all p &lt; 0 .050). There were group-by-time interactions (all p &lt; 0 .050) for all ventilatory submaximal values. Significant group and time differences were observed for VE; RER; respiratory rate (RR); VEqO2; PETO2; VO2, and VT (all p &lt; 0 .050). There were also group-by-time interactions (all p &lt; 0 .050) and group and time differences for SBP, mean arterial blood pressure (MAP) and HR (all p &lt; 0.010).

Conclusion: During submaximal exercise, we verified a compensatory response of HR, and greater VE and VO2 in the individuals with DS. In addition, we were able to observe that the DS group had a reduced SBP and MAP response to submaximal exercise. On the other hand, we found that adults with DS have lower peak hemodynamic and cardiorespiratory values, and a lower cardiac reserve. Further research is warranted to investigate the effects of these results on the general health of adults with DS and the impact of long-term exercise programs on these parameters.

The Effects of Resistance Training on Physical Fitness and Neuromotor-Cognitive Functions in Adults With Down Syndrome

Adults with Down syndrome are an underserved population at high risk for a host of different pathologies from aging and lack of activity.

Blunted autonomic response to standing up and head-up tilt in individuals with intellectual disabilities

Previous research suggests individuals with intellectual disabilities (ID) may experience autonomic dysfunction, however, this has not been thoroughly investigated. The aim of this study was to compare the autonomic response to standing up (active orthostasis) and head-up tilt (passive orthostasis) in individuals with ID to a control group without ID. Eighteen individuals with and 18 individuals without ID were instrumented with an ECG-lead and finger-photoplethysmography for continuous heart rate and blood pressure recordings. The active and passive orthostasis protocol consisted of 10-min supine rest, 10-min standing, 10-min supine recovery, 5-min head-up tilt at 70°, followed by 10-min supine recovery. The last 5 min of each position was used to calculate hemodynamic and autonomic function (time- and frequency-domain heart rate and blood pressure variability measures and baroreflex sensitivity). Individuals with ID had higher heart rate during baseline and recovery (P < 0.05), and an attenuated hemodynamic (stroke volume, heart rate) and heart rate variability response to active and passive orthostasis (interaction effect P < 0.05) compared with individuals without ID. Mean arterial pressure (MAP) was higher in individuals with ID at all timepoints. Individuals with ID demonstrated altered hemodynamic and autonomic regulation compared with a sex- and age-matched control group, evidenced by a higher mean arterial pressure and a reduced response in parasympathetic modulation to active and passive orthostasis.NEW & NOTEWORTHY Individuals with ID demonstrated altered hemodynamic and autonomic regulation to the clinical autonomic function tasks standing up and head-up tilt (active and passive orthostasis). Higher resting heart rate and higher MAP throughout the protocol suggest a higher arousal level, and individuals with ID showed a blunted response in parasympathetic modulation. Further research should investigate the relationship of these findings with clinical outcomes.

Changing Landscape of Congenital Heart Disease

Congenital heart disease is the most frequently occurring congenital disorder affecting ≈0.8% of live births. Thanks to great efforts and technical improvements, including the development of cardiopulmonary bypass in the 1950s, large-scale repair in these patients became possible, with subsequent dramatic reduction in morbidity and mortality. The ongoing search for progress and the growing understanding of the cardiovascular system and its pathophysiology refined all aspects of care for these patients. As a consequence, survival further increased over the past decades, and a new group of patients, those who survived congenital heart disease into adulthood, emerged. However, a large range of complications raised at the horizon as arrhythmias, endocarditis, pulmonary hypertension, and heart failure, and the need for additional treatment became clear. Technical solutions were sought in perfection and creation of new surgical techniques by developing catheter-based interventions, with elimination of open heart surgery and new electronic devices enabling, for example, multisite pacing and implantation of internal cardiac defibrillators to prevent sudden death. Over time, many pharmaceutical studies were conducted, changing clinical treatment slowly toward evidence-based care, although results were often limited by low numbers and clinical heterogeneity. More attention has been given to secondary issues like sports participation, pregnancy, work, and social-related difficulties. The relevance of these issues was already recognized in the 1970s when the need for specialized centers with multidisciplinary teams was proclaimed. Finally, research has become incorporated in care. Results of intervention studies and registries increased the knowledge on epidemiology of adults with congenital heart disease and their complications during life, and at the end, several guidelines became easily accessible, guiding physicians to deliver care appropriately. Over the past decades, the landscape of adult congenital heart disease has changed dramatically, which has to be continued in the future.

Assessment of cardiac function in absence of congenital and acquired heart disease in patients with Down syndrome

BACKGROUND

Extra genetic material in patients with Down syndrome (DS) may affect the function of any organ system. We evaluated cardiac functions using conventional tissue Doppler and two-dimensional speckle tracking echocardiography in patients with DS in the absence of congenital and acquired heart disease in patients.

METHODS

A total of 115 patients with DS between 6 and 13 years of age with clinically and anatomically normal heart and 55 healthy children were included in this cross-sectional study. DS was diagnosed by a karyotype test. Patients with mosaic type were not included in this study. Systolic and diastolic functions were evaluated by echocardiography.

RESULTS

Pulsed waved Doppler transmitral early/late inflow velocity (E/A), tissue Doppler mitral annular early/late diastolic peak velocity (Ea/Aa), transtricuspid E/A and tricuspid valve annulus Ea/Aa, pulmonary venous Doppler systolic/diastolic (S/D) wave ratio were lower in patients with Down syndrome than in the control group (P=0.04, P=0.001, P<0.05, P<0.001, P<0.001, respectively). Mitral and tricuspid annular Ea were lower in patients with DS (P<0.001). The right and left ventricular myocardial performance indexes were higher in patients with DS than in the controls (P<0.01). They had significantly higher left ventricular mass, ejection fraction, the mitral annular plane systolic excursion values. However, the Down syndrome group compared with the controls had a lower strain values examined by two-dimensional longitudinal speckle-tracking strain echocardiography.

CONCLUSION

These findings suggest conventional tissue Doppler and two-dimensional longitudinal speckletracking strain echocardiography were useful methods of investigating ventricular function and identifying a higher incidence of biventricular dysfunction in patients with Down syndrome compared with the healthy controls.

Cardiorespiratory fitness in individuals with intellectual disabilities--a review

Cardiorespiratory fitness is the ability of the circulatory, respiratory and muscular systems to supply oxygen during sustained physical activity. Low cardiorespiratory fitness levels have been found in individuals with intellectual disabilities (ID), which puts them at higher risk for cardiovascular diseases and all-cause mortality. The aims of this review were to update previous reviews about (a) the cardiorespiratory fitness levels and their determinants in individuals with ID, and (b) the validity and reliability of cardiorespiratory fitness testing in individuals with ID. We searched the databases of Pubmed and Embase for relevant studies, resulting in 31 included articles. These studies mainly included younger participants with mild to moderate ID. Results confirmed previous findings of low cardiorespiratory fitness levels in individuals with ID. Cardiorespiratory fitness levels of children and adolescents with ID are already low, with further decline with increasing age. Furthermore, females have lower cardiorespiratory fitness levels than males. Physical inactivity and chronotropic incompetence are most likely to contribute to low cardiorespiratory fitness levels. Peak cardiorespiratory fitness levels of individuals with ID can be assessed with maximal treadmill protocols, after allowing for familiarization sessions. Although, predicting maximal oxygen uptake from field tests is problematic, field tests have been found valid and reliable as indicators of cardiorespiratory fitness.