Discussion

This single-centre, retrospective cohort study sought to describe the prevalence and evaluate the risk of obesity in a subset of surgically corrected CHD subjects between 2004 and 2017. Obesity and overweight have arisen as a significant public health concern over the past several decades, with a unique risk to children with CHD. Studies have demonstrated that paediatric patients with CHD generally have elevated prevalences of obesity compared to the general population. ^{Reference Briston, Sabanayagam and Zaidi11–Reference Steele, Preminger and Erenberg14} This study re-demonstrated this significantly increased prevalence of both overweight (36.2%) and obesity (20.8%). Furthermore, this study showed that in comparing recent eras, the risk of development of both overweight and obesity for all CHD subjects increased with time. This is a similar trend to what is seen nationally, ^{Reference Stierman, Afful and Carroll23} and emphasises the growing evidence that overweight and obesity are prominent sources of morbidity in CHD. Perhaps more concerning is the progressive trend of earlier onset of overweight and obesity as seen with this cohort.

Coarctation of the aorta was the only diagnosis of those included that was found to have a significantly higher prevalence of obesity compared to other forms of CHD. This subgroup is particularly vulnerable to the increasing risk of obesity in the more modern era cohorts. There is no evident physiologic reason for this difference, and study criteria excluded those with underlying genetic diagnoses predisposing to elevated Body Mass Index, as well as those with significant concomitant cardiac anomalies such as a bicuspid aortic valve. Individuals with coarctation of the aorta do remain at risk of hypertension at rest and with exercise, as well as more devastating complications such as aortic aneurysm, dissection, or rupture. ^{Reference Van Hare, Ackerman and Evangelista24} The strong correlation between obesity and hypertension, left ventricular hypertrophy, and aortic dilation ^{Reference Jackson, Ph and Fox26} may only further increase these risks. These patients may be at particular risk for poor outcomes from obesity-related morbidity.

The distribution of obesity across different eras was comparable to that of general population and prior studies. Our cohort found the overall prevalence of obesity was lower (12.6%) between 2014–2017 compared to the overall prevalence 20.8% (2004–2017), and is near identical to the prevalence of obesity found in the NHANE 2017–2020 survey in those ages 2 to 5 years old (12.7%). ^{Reference Stierman, Afful and Carroll23} These subjects would be expected to have a lower prevalence of obesity as the steepest rise in Body Mass Index has previously been found to occur between ages 6 and 9, and further increase into adolescence. ^{Reference Umer, Kelley, Cottrell and Giacobbi4,Reference Kim, Jae and Choo9,Reference Stierman, Afful and Carroll23,Reference Cunningham, Kramer and Narayan27} Older cohorts of 2004–2008 as well as 2009–2013 (24.1% and 25.3%, respectively) were found to have a prevalence of obesity similar to prior studies. ^{Reference Kim, Jae and Choo9}

Several plausible hypotheses regarding this increased risk of obesity have been posed previously. It is possible that this association is driven by environmental factors affecting exercise. ^{Reference O’Byrne, Mcbride and Paridon8} The American Heart Association has published recommendations ^{Reference Van Hare, Ackerman and Evangelista24} for sports participation in children with CHD. Subjects with repaired ventricular septal defect are recommended for full participation if there is little to no residual defect and absence of pulmonary hypertension. Subjects repaired tetralogy of Fallot and d-transposition of the great arteries are recommended to have evaluation with electrocardiography, ventricular function and exercise testing, with exercise restriction if evidence is found of exercise-induced arrhythmias, hypotension, ischaemia, or ventricular dysfunction. In addition, subjects with repaired coarctation of the aorta are recommended to undergo similar testing, including either magnetic resonance imaging or computed tomography angiography, as well as gradient systolic blood pressure measurements prior to participation. ^{Reference Van Hare, Ackerman and Evangelista24,Reference Curran, Hansen and Lindsey25} For all repaired CHD, recommendations for thorough evaluation, especially those requiring specialised testing, may delay or inhibit clearance for sport participation. This barrier is particularly high for the coarctation of the aorta population, with restricted exercise limited to low-intensity activities only. Indeed, in the absence of specific exercise restrictions from a cardiac provider, some patients and families may elect to self-restrict due to ambiguity or concerns.

This rigour of testing may delay or fully deter some from engaging in appropriately intense exercise. A study of exercise tolerance and risk aversion in the Fontan population demonstrated that around half of parents are concerned about sports participation for their child, though there was notably no significant difference between athletes and non-athletes. ^{Reference Baleilevuka-hart, Khader and Gonzalez De Alba18} This risk aversion may similarly hinder involvement by children with coarctation of the aorta, even when recommended for full participation. Exercise in childhood is an integral component to many proposed and studied weight interventions, ^{Reference Wang, Cai and Wu28,Reference Motevalli, Drenowatz and Tanous29} leads to further involvement in exercise in adulthood, ^{Reference Perkins, Jacobs and Barber30,Reference Jose, Blizzard and Dwyer31} and has been associated with decreased Body Mass Index, ^{Reference Logan, Lloyd and Schafer-kalkho32} improved quality of life, ^{Reference Vella, Cliff and Magee33} and decreased cardiovascular risk. ^{Reference Hebert, Klakk and Møller34} While sport restriction may be warranted following specialist evaluation, it is similarly important to identify safe exercise and promote regular involvement in these activities. ^{Reference Baleilevuka-hart, Khader and Gonzalez De Alba18,Reference Longmuir, Brothers and de Ferranti20,Reference Perkins, Jacobs and Barber30} Active practice of activity prescriptions by cardiac providers may further augment exercise participation.

Nutritional status is an area of close scrutiny as children with CHD grow. In both the pre-operative period and subsequent first years of life, there is an emphasis on promoting nutritional status as measured by weight gain to manage the perioperative state and optimise cognitive growth. ^{Reference Toole, Toole and Kyle35–Reference Kogon, Ramaswamy and Todd37} This was seen in our cohort, though interestingly at lower prevalences than previously reported prevalences of 40–60%. ^{Reference Toole, Toole and Kyle35,Reference Kogon, Ramaswamy and Todd37} These feeding difficulties are a source of family anxiety and patient morbidity, particularly in the post-operative period. ^{Reference Wright, Phillips and Matthews38} As patients pass this critical period of nutritional intervention, focus within multidisciplinary CHD clinics may shift away from preemptive management of weight. Meanwhile, patient and family concerns regarding weight continue throughout early childhood and adolescence, including culturally driven views of higher weight indicating improved health. ^{Reference Kaufman and Karpati39,Reference Baughcum, Burklow and Deeks40} Regular specialist clinic visits throughout childhood remain an opportunity for intervention by multidisciplinary teams, including education regarding the unique importance of normal weight in this population.

This study had several limitations. First, the data were sampled from a single tertiary centre, limiting the diversity of the patient population as well as the overall sample size. This is a limited robust analysis of subgroups of diagnosis and era. Most notably, this was seen in the analysis of tetralogy of Fallot, which had an incidence of 0% obesity in the time cohort 2014–2017. While this does limit the power of analysis, this centre serves a large number of post-surgical cardiac patients in the state of Oregon and Southwest Washington, potentially decreasing sampling bias. This study was retrospective in nature; thus, there were no specific time points of data to indicate the onset of overweight and obesity. It is possible that patients met criteria for these categories prior to their otherwise scheduled hospital encounters. This is alleviated to some extent by the need for frequent follow-up for corrected CHD patients, particularly in the first several years of life. Third, Body Mass Index was compared to a fixed prevalence of 13.7% as published for the State of Oregon in a 2019–2020 survey, as opposed to matched healthy controls. ⁴² This may have allowed for more descriptive analysis of the change in obesity, both for the general population as well as those with CHD. While these controls could have been identified, they lacked adequate follow-up to identify the onset of overweight or obesity with accuracy. As this population largely contains individuals living in Oregon, this fixed prevalence is believed to closely represent the expected prevalence of obesity for this cohort. Finally, Body Mass Index is known to be an imperfect surrogate for overall health and cardiovascular comorbidities. Prior studies, however, have demonstrated a relationship between paediatric Body Mass Index and the development of early atherosclerosis on autopsy evaluation, ^{Reference Herridge, Tedesco-bruce and Gray43} cardiovascular morbidity in childhood, and subsequent cardiovascular disease in adulthood. ^{Reference Umer, Kelley, Cottrell and Giacobbi4} While other methods may more directly measure the progression of cardiovascular risk in this at-risk population, this surrogate demonstrates the ongoing disparity between those with CHD and the general population.