Autonomic control of heart rate in children with congenital heart disease
Date
2023-02-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0001-8879-7656
Type
Thesis
Degree Level
Masters
Abstract
Congenital heart disease (CHD) is the leading form of birth defects worldwide. Advancements in neonatal management and surgery have led to better outcomes for all types of CHD lesions. Children with CHD may demonstrate autonomic dysfunction indicated by a reduction in heart rate variability (HRV) at rest and delayed heart rate recovery (HRR) post-exercise compared to healthy children. We postulate that children with CHD may not engage in regular physical activity and have a higher body mass index (BMI) compared to healthy children, due to several causes. It is not known whether children with CHD matched with healthy control children on age, BMI, and physical activity will exhibit autonomic dysfunction. HYPOTHESES: We tested three hypotheses: Compared to age, BMI matched healthy controls, and with approximately similar self-reported physical activity levels, (1) children with CHD would have reduced heart rate variability at rest; (2) children with CHD would have slower heart rate recovery kinetics following the six-minute walk test; and (3) there would be a significant correlation between resting heart rate variability and heart rate recovery kinetics. METHODS: Eighteen children with CHD (f/m=7/11) were matched on age, BMI, and approximately similar physical activity (using the Physical Activity Questionnaire for Older Children, PAQ-C) with 18 healthy control children (CTL) (f/m=10/8). Heart rate variability (HRV) was determined following 10-min (minutes) of supine rest using a 5-min surface electrocardiogram (ECG) recorded epoch. Post-exercise HRR kinetics were determined following a 6-min walk test (6MWT) over a 4-min period using telemetry-based HR. Mono-exponential modelling was used to derive the HRR time constant (time to reach 63% change). Analyses included unpaired t-tests for demographics, HRV, 6MWT distance, 6MWT HR, and post-exercise HRR kinetics between the two groups. ANOVA and ANCOVA (with physical activity as the covariate) were used to compare group differences. Factorial ANOVA was used to analyze differences between the groups on exercise HR. Multiple linear regression was used to determine the relationship between 6MWT HR and HRV, 6MWT distance and HRV, and between HRR time constant and HRV. Simple linear regression was used to determine the relationship between 6MWT distance and average 6MWT HR with HRR. Data are presented as mean±SD and P < 0.05 was considered significant. RESULTS: There was no statistically significant difference between children with CHD and CTL on age (12±2 years vs. 11±3 years, P = 0.6245), BMI (19±3 vs. 19±4, P = 0.8456), and physical activity (3.06±0.77 vs. 3.48±0.55, P = 0.0646). On average, children with CHD had a lower resting SDRR (standard deviation of R-R intervals, 62±41 ms vs. 92±24 ms; P = 0.0093), lower 6MWT distance (528±53 m vs. 608±81 m; P = 0.0013), lower average 6MWT HR (120±12 beats/min vs. 138±17 beats/min; P < 0.001), lower end-exercise HR (127±14 beats/min vs. 149±19 beats/min; P < 0.001), lower recovery amplitude (39±14 beats/min vs. 57±15 beats/min, P < 0.001) and higher HRR time constant (33±15 s vs. 24±8 s; P = 0.0334) compared to CTL. When accounting for variance from PAQ-score, there was a difference between the groups on SDRR (P = 0.0331) but no difference between the groups on HRR (P = 0.0809). Heart rate was lower throughout the 6MWT at each minute of exercise in CHD vs. CTL (all P < 0.005). Of all HRV parameters, SDRR had the strongest relationship with 6MWT distance (r = 0.347, P = 0.0382) and HRR time constant (r = - 0.350, P = 0.0365). Inspection of SDRR indicated 7/18 children with CHD had an SDRR above the group mean SDRR in CHD and within or above the SD of the SDRR of CTL. The CHD subgroup with high SDRR reported a higher PAQ-score compared to CHD subgroup with low SDRR (3.50±0.71 vs. 2.78±0.69; P = 0.0485). CONCLUSION: Our findings demonstrate that children with CHD often have a lower HRV at rest, but not in all cases. Children with CHD and relatively high SDRR report higher levels of physical activity compared to their counterparts with relatively lower SDRR. On average, children with CHD display lower HR during exercise, and this coincides with reduced 6MWT distance. The HRR is slower in children with CHD compared to healthy matched CTL which may be related to resting SDRR; however, the slower HRR in children with CHD is more comparable to CTL when accounting for self-reported physical activity. Collectively, these data indicate that cardiac autonomic dysfunction is commonplace in children with CHD and may be influenced by physical activity.
Description
Keywords
congenital heart disease, heart rate variability, heart rate recovery, age, BMI, physical activity, physical activity questionnaire, 6-minute walk test, autonomic dysfunction.
Citation
Degree
Master of Science (M.Sc.)
Department
Kinesiology
Program
Kinesiology