Advances in pediatric cardiology have allowed the early diagnosis and better therapeutic options for children with congenital heart disease. Consequently, these patients live longer, with an increase in the number of adults with this condition, who are subject to complications not only of the primary disease, but also of atherosclerotic cardiovascular diseases (CVD). ^{1 , 2}

Clinical manifestations of CVD are caused by a progressive atherosclerotic process, with a long preclinical phase that may last decades. ³ According to the multicentric study Pathobiological Determinants of Atherosclerosis in Youth (PDAY), in which a risk scores for subclinical atherosclerosis in inviduals aged 15 to 34 years was constructed, risk factors for atherosclerosis in young individuals are comparable to those in older adults and the elderly. ⁴

Dyslipidemia is considered one of the main predictors of CVD. ⁵ There is robust evidence that increased high-density lipoprotein cholesterol (HDL-c) levels reduce the relative risk of CVD, mainly due to their cardiovascular protective effects, such as the reverse cholesterol transport, the stabilizing effect on the endothelium and the antioxidant activity. ^{5 , 6} Besides, important negative associations between HDL-c and inflammatory markers – surgery, obesity, repeated infections and C-reactive protein – have been demonstrated. ⁷

It is estimated that at least one fourth of patients with congenital heart disease are physically inactive, either because of clinical limitations or excessive care by their caregivers. ^{8 , 9} In addition, these patients are more susceptible to inflammation, due to complications of interventions, or due to acute infections, mainly with pulmonary involvement. ^{10 , 11}

Since atherosclerosis is often asymptomatic in children, the risks of this condition may be underestimated by health professionals. Thus, the identification of the risk factors for atherosclerosis is fundamental, and prospective studies have suggested that the earlier the intervention, the better the prevention of atherothrombotic events. ^{12 , 13}

This study aimed to describe the prevalence of HDL-c levels and to assess their correlation with socioeconomic and clinical characteristics, and cardiovascular risk factors in children and adolescents with congenital heart disease.

This was a cross-sectional study. Individuals aged 5 to 18 years with congenital heart disease, in the late postoperative period (>6 months) after interventional catheterization or cardiac surgery, were considered eligible for the study. Patients attending routine clinical visits in two pediatric cardiology outpatient clinics in the state of Santa Catarina, Brazil, between August and December 2016 were recruited.

Exclusion criteria included secondary diagnosis of malignant neoplasm, chromosomal abnormalities, familial hypercholesterolemia, diabetes mellitus, hypothyroidism, other inflammatory chronic diseases and acute inflammatory diseases in the last 15 days.

A total of 232 individuals were included; most were older than 10 years (52.2%), female (52.6%) and white (87.1%). Most patients had acyanotic congenital heart disease (65.9%), with ventricular septal defect as the most common (15.9%). All patients had undergone a cardiac invervention at least six months before, 82.3% a cardiac surgery and 17.7% therapeutic catheterization. Nineteen percent of patients had more than two hospitalizations for community-acquired infections.

Table 1 describes the distribution of HDL-c levels by sociodemographic and clinical characteristics. Patients ≥ 10 years of age showed significantly lower concentrations of HDL-c compared with patients younger than 10 years. Patients with acyanotic congenital heart disease showed significantly higher levels of HDL-c as compared with patients with cyanotic congenital heart disease.

Table 1

Variables		N	Mean	95% CI	p*
Sociodemographic characteristics
Age	< 10 years ≥ 10 years	111 121	53.5 49.1	45.0-62.0 39.0-57.0	0.01
Sex	Female Male	122 110	52.0 50.3	43.8-59.0 40.0-61.3	0.31
Skin color	White Others	202 30	51.1 51.7	42.0-59.0 40.7-63.3	0.81
Per capita income	<1 minimum wage ≥ 1 minimum wage	157 75	50.5 52.6	41.0-58.0 45.0-63.0	0.24
Maternal education†	< 10 years ≥ 10 years	99 131	50.8 51.7	42.0-60.0 42.0-61.0	0.60
Clinical characteristics
Type of congenital heart disease	Cyanotic Acyanotic	79 153	48.8 52.4	41.0-57.0 43.0-63.0	0.04
Type of cardiac interventional procedure	Catheterization Surgery	41 191	53.2 50.8	46.0-62.0 41.0-59.0	0.25
Use of medications	No Yes	175 57	51.7 49.8	39.5-59.5 43.0-60.0	0.32
Number of hospitalizations for community-acquired infections	≤ 2 >2	187 45	51.3 50.84	42.0-59.0 39.0-61.5	0.85
Family history of early coronary artery disease ‡	Negative Positive	177 51	51.3 50.8	41.0-61.5 43.0-57.0	0.80

95% CI = 95% confidence interval

Mean HDL-c was 51.2 mg/dL (SD 12.6); 23.3% of patients showed borderline levels and 9.9% showed low HDL-c levels; 33.2% of children and adolescents with congenital heart disease showed undesirable HDL-c levels. The following cardiovascular risk factors were found to be associated with low HDL-c levels – being insufficiently active, screen time longer than two hours per day, passive smoking, abdominal obesity, positive family history of cardiovascular disease, borderline glucose levels, and increased hs-PCR. The distribution of cardiovascular risk factors by HDL-c classification are described in Table 2 .

Table 2

Cardiovascular risk factors *	Reference	Total n (%)	HDL-c classification
			Desirable n (%) 155 (66.8)	Borderline n (%) 54 (23.3)	Low n (%) 23 (9.9)
Total cholesterol	Desirable (<170 mg/dL)	184 (79.3)	114 (73.5)	48 (88.9)	22 (95.7)
	Borderline (170-199 mg/dL)	43 (18.5)	37 (23.9)	5 (9.3)	1 (4.3)
	High (≥ 200 mg/dL)	5 (2.2)	4 (2.6)	1 (1.9)	0 (0)
LDL-Cholesterol	Desirable (<110 mg/dL)	185 (79.7)	124 (80)	44 (81.5)	17 (73.9)
	Borderline (110-129 mg/dL)	31 (13.4)	22 (14.2)	5 (9.3)	4 (17.4)
	High (>130 mg/dL)	16 (6.9)	9 (5.8)	5 (9.3)	2 (8.7)
Non-HDL-Cholesterol	Desirable (<120 mg/dL)	174 (75)	119 (76.8)	40 (74.1)	15 (65.2)
	Borderline (120-144 mg/dL)	36 (15.5)	23 (14.8)	8 (14.8)	5 (21.7)
	High (≥145 mg/dL)	22 (9.5)	13 (8.4)	6 (11.1)	3 (13.0)
Triglycerides	Desirable *	179 (77.2)	122 (78.7)	40 (74.1)	17 (73.9)
	Borderline *	38 (16.4)	22 (14.2)	13 (24.1)	3 (13)
	High *	15 (6.5)	11 (7.1)	1 (1.9)	3 (13)
Fasting glucose	Desirable (<100 mg/dL)	201 (86.6)	137 (88.4)	45 (83.3)	19 (82.6)
	Borderline (>100 and < 126 mg/dL)	31 (13.4)	18 (11.6)	9 (16.7)	4 (17.4)
hs-CRP†	Low risk (<1 mg/L)	82 (35.7)	69 (44.5)	11 (20.4)	2 (8.7)
	Moderate risk (1 - 3 mg/L)	119 (51.7)	73 (47.1)	32 (59.3)	14 (60.9)
	High risk (≥ 3 mg/L)	29 (12.6)	13 (8.4)	10 (18.5)	6 (26.1)
Systolic blood presusure	Desirable (≤ 90 th percentile)	227 (97.8)	151 (97.4)	53 (98.1)	23 (100)
	Borderline (>90 th percentile)	3 (1.3)	2 (1.3)	1 (1.9)	0 (0)
	High (≥ 95 th percentile)	2 (0.9)	2 (1.3)	0 (0)	0 (0)
Diastolic blood pressure	Desirable (≤ 90 th percentile)	227 (97.8)	153 (98.7)	52 (96.3)	22 (95.7)
	Borderline (>90 th percentile)	3 (1.3)	1 (0.6)	1 (1.9)	1 (4.3)
	High (≥ 95 th percentile)	2 (0.9)	1 (0.6)	1 (1.9)	0 (0)
Physical activity ‡	Active (Score 1 - 3)	10 (4.4)	6 (3.9)	2 (3.7)	2 (8.7)
	Insufficiently active (Score 4 - 5)	217 (95.6)	144 (92.9)	52 (96.3)	21 (91.3)
Screen time	< 2 hours/day	109 (47)	71 (45.8)	26 (48.1)	12 (52.2)
	≥ 2 hours/day	123 (53)	84 (54.2)	28 (51.9)	11 (47.8)
Passive or active smoking §	No	172 (75.1)	114 (73.5)	41 (75.9)	17 (73.9)
	Yes	57 (24.9)	39 (25.2)	12 (22.2)	6 (26.1)
BMI/age	Normal (< +1 z-score)	188 (81.0)	125 (80.6)	47 (87)	16 (69.6)
	Overweight / obesity (≥+1 z-score)	44 (19.1)	30 (19.4)	7 (13)	7 (30.4)
Waist circumference //	Desirable (<75 percentile)	170 (73.3)	113 (72.9)	44 (81.5)	13 (56.5)
	Abdominal obesity (≥75 percentile)	57 (24.6)	38 (24.5)	9 (16.7)	10 (43.5)

LDL: low-density lipoprotein; BMI/age: body mass index-for-age; hs-CRP: high-sensitivity C-reactive protein.

Table 3 shows the results of the bivariate analysis among socioeconomic, clinical and cardiovascular risk factors and undesirable HDL-c levels. Age and hs-PCR showed significant associations with undesirable HDL-c levels.

Table 3

Variable	Risk factor	chi-square	p
Sociodemographic characteristics
Age	≥ 10 years	4.79	0.03
Sex	Male	3.29	0.07
Skin color	Non-white	0.19	0.66
Per capita income	<1 minimum wage/person	2.13	0.15
Maternal education	<10 years	0.60	0.44
Clinical characteristics	Acyanotic	2.89	0.09
Type of heart disease	Cardiac surgery	2.84	0.09
Type of procedure	Yes	2.71	0.10
Use of medications	>2 times	1.17	0.28
Number of hospitalizations for community-acquired infections
Family history of early coronary heart disease	Positive	0.01	0.94
Cardiovascular risk factors
Total cholesterol	≥170 mg/dL	0.40	0.53
LDL-cholesterol	≥110 mg/dL	0.02	0.89
Non-HDL-cholesterol	≥120 mg/dL	0.78	0.38
Triglycerides	≥75/≥90 mg/dL *	0.64	0.42
Fasting glucose	≥100 mg/dL	0.001	0.98
hs-CRP	≥3 mg/L	7.68	0.01
Systolic blood pressure	Hipertension	1.00†	1.00
Diastolic blood pressure	Hipertension	0.26†	1.00
Physical activity	Inactive	0.17†	0.74
Screen time	≥2 hours/day	0.26	0.61
Passive smoking	Yes	0.09	0.77
BMI/age	≥ +1 z-escore	0.05	0.83
Waist circumference	≥ 75 th percentile	0.001	0.98

BMI/age: body mass index-for-age; hs-CRP: high-sensitivity C-reactive protein

In the multivariate logistic regression analysis – adjusted for sex, income, type of congenital heart disease, type of procedure, number of hospitalizations for community-acquired infections, use of medications, waist circumference, C-reactive protein ≥3 mg/L, age ≥ 10 years and triglycerides ≥75/≥90 mg/dL (according to age) were associated with HDL-c levels, as shown in Table 4 .

Table 4

	Undesirable HDL-c (<40 mg/dL)
	Unadjusted			Adjusted *
Risk factors
hs-CRP
<3.0 mg/L	1			1
≥3.0 mg/L	2.96	1.34-6.54	0.01	3.26	1.32-8.04	0.01
Age
<10 years	1			1
≥10 years	1.86	1.06-3.25	0.03	2.11	1.12-3.99	0.02
Triglycerides
<75 /<90 mg/dL 1	1			1
≥75 /≥90 mg/dL 1	1.30	0.69-2.46	0.42	2.21	1.13-4.75	0.04

hs-CRP: high sensitivity C-reactive protein

This cross-sectional study showed an important prevalence of dyslipidemia in children and adolescents with congenital heart disease, mainly attributed to low HDL-c levels (9.9% of patients with low HDL-c levels, mean 51.2 mg/dL, 95% CI 38.6-63.8 mg/dL). These findings contrast with two previous studies with children with congenital heart disease conducted in 2013 – one of them was a cross sectional study ²⁷ carried out in São Paulo State/Brazil with 52 children with congenital heart disease, in which no significant changes in HDL-c levels were observed in this group by the authors; another study was a case-control study conducted in Iran, which showed that the group with congenital heart disease (case group) had significantly higher mean HDL-c levels than the group without the disease (control group). ²⁸ Further studies are needed to clarify these differences.

In the present study, mean HDL-c level was 51.2 mg/dL (SD 12.6). In an apparently healthy group of 1,009 children and adolescents in the city of Florianopolis, ²⁹ Brazil, in 2009, mean HDL-c level was 53.4 mg/dL (95% CI 52.6-54.2 mg/dL), but the prevalence of undesirable HDL-c (<45 mg/dL) was lower (23%) than in our study (33.25). This difference may be explained by the higher exposure of children and adolescents with congenital heart disease to inflammatory stimuli – therapeutic procedures, infections – that demand the production of several pro-inflammatory mediators at expenses of HDL-c synthesis ³⁰ – in addition to greater restrictions on exercise and diet, with is supported by the literature. ^{25 , 31}

In addition, we found that patients with cyanotic congenital heart disease had lower HDL-c levels in comparison with patients with acyanotic congenital heart disease. So far, no study has evaluated HDL-c levels and type of heart disease. In a prospective study ¹¹ with patients aged 8-19 years old with a history of severe congenital heart disease, a higher probability of low HDL-c (<40 mg/dL) was found in these patients (RR 1.79 [1.36-2.35]) compared with healthy children in the same age range, but no comparative analysis was made between cyanotic and acyanotic heart diseases.

The Brazilian Study of Cardiovascular Risks in Adolescents (ERICA, Estudo de Risco Cardiovascular em Adolescentes ) determined the prevalence of cardiovascular risk factors in adolescents in the country. The study revealed a high prevalence of dyslipidemia, mainly of low HDL-c, followed by increased TC levels. The prevalence of low HDL-c was significantly higher in the North and Northeast regions, where the Human Development Index is the lowest, a similar trend to that found in developing countries. ³² In the last years, a historical trend of improvement in HDL-c levels has been observed in developed countries, where the environmental stress seems to be more controlled. This trend contrasts with that found in developing countries, but with no direct relationship between low HDL-c and the prevalence of obesity or metabolic syndrome in these populations, which could also explain this behavior. Another study, the National Health and Nutrition Examination Survey (NHANES), showed a decrease in the prevalence of undesirable lipid levels in the American pediatric population, including low HDL-c, from 17.9% (1999-2000) to 12.8% (2011-2012). ^{33 , 34} In contrast, in Taiwan, there was an increase in low HDL-c levels from 6.5% in 1996 to 11.6% in 2006. ³⁵ In Forianopolis, an increase in the prevalence of low HDL-c was seen in children, from 5% in 2001 to 23% in 2009. ^{29 , 36} It is of note that high HDL-c levels in children and adolescents observed in developed countries like Spain and Japan ha been associated with relatively low mortality for CVD in developed countries. ^{37 , 38}

These differences in HDL-c found in different geographic locations may be due to several factors, including genetic and dietetic factors, as physical activity, and environmental stress, facilitating the exposure of children to inflammatory stimuli. Better public policies are usually implemented in developed countries, including awareness-raising programs for healthy diet, exercise, and obesity control. Studies ^{29 , 32} have suggested that heredity may have a strong impact on HDL distribution in Brazil, due to its great ethnic diversity.

Also, studies ^{33 , 34} have shown an inverse relationship between HDL-c levels and age. ^{33 , 34} Studies of the second half of the 20th century, like the Bogalusa Heart Study, ³ demonstrated, in a sample of children, that increase in age was associated with a decrease in HDL-c levels. ³ This is in accordance with our results, that showed an association between age ≥ 10 years and undesirable HDL-c levels. It is possible that the contemporary lifestyle is associated with a greater exposure to inflammatory stimuli, since early childhood, exemplified by repeated infections of pre-school children attending day care centers. However, further studies on environmental and clinical factors of patients with congenital heart disease are needed, to develop strategies for controlling the variables responsible for the reduction of HDL-c levels in the studied patients.

In addition, data highlighting the obesity pandemic have reported a high prevalence of elevated triglyceride levels in children in both developed and developing countries. ³⁹ One of the most accepted definitions of metabolic syndrome in children is the co-occurrence of insulin resistance, arterial hypertension, dyslipidemia (increased triglyceride and decreased HDL-c levels) and abdominal obesity. ⁴⁰ Obesity per se causes a metabolic disturbance, which combined with an elevation of triglycerides, culminates in a persistent inflammatory state and decreased HDL-c levels. ⁴¹

Similarly to the study by Giuliano et al., ²⁹ we showed an inverse relationship between low HDL-c and high triglyceride levels. This pattern of dyslipidemia has been described as the most common in contemporary children. ³⁹ In another study, the authors evaluated data from the National Health and Nutrition Examination Survey (NHANES), of children aged 5-19 years, and confirmed that the increase in age is accompanied by an increase in the prevalence of hypertriglyceridemia, especially in overweight and obese individuals. ^{33 , 34} This may be explained by the high proportion of children who are insufficiently active and have poor dietary habits (e.g. a trans fatty acid-rich diet), which is in fact a world trend. These individuals become more exposed to such inflammatory stimuli over time.

Our sample showed increased levels of hs-CRP, which may be a result of surgical stress, increased vulnerability to repeated infections, and elevation in triglyceride concentrations, associated with a sedentary lifestyle and high intake of trans-fatty acids. Similarly to previous studies, ^{25 , 29} increased hs-CRP was associated with a higher risk of undesirable HDL-c levels, which may be explained by a deviation in the metabolic pathway during the synthesis of acute phase proteins, which leads to suppression of hepatic lipoprotein production, particularly HDL. ^{25 , 29}

Increasing evidence has shown an association of low family income and low maternal education with low HDL-c levels, probably related to a subclinical inflammatory status, demonstrated by elevations in hs-CRP. These social determinants of health are related to the inflammatory process that accelerates atherosclerosis progression. On the other hand, it is known that established atherosclerosis per se – presence of complex plaques, fibrosis and calcification – is associated with low hs-CRP, leading to a vicious circle. ^{11 , 42 , 43}

This study has some limitations that should be considered. The cross-sectional design of the study precludes inferences regarding the causes of low HDL-c levels, and the absence of a control group does not allow more detailed comparisons. Also, there are other cofounding factors that were not evaluated in the present study, including assessment of sleep, place of residence (rural and urban), and genetic factors.

This is the first Brazilian study to describe the distribution of HDL-c concentrations in a representative sample of patients with congenital heart disease, and to demonstrate the relationship of HDL-c levels with socioeconomic, clinical, and cardiovascular risk factors. The investigation of HDL-c in patients with congenital heart disease is important to determine the risk of atherosclerotic disease and to elucidate whether the underlying disease (combined with the exposure to inflammatory stimuli of therapies or their clinical conditions) would put these patients at high risk for CVD at adulthood. Therefore, understanding the role of each cardiovascular risk factor is crucial in the management of patients with congenital heart disease.

In the present study on children and adolescents with congenital heart disease, almost one third of patients showed borderline or low levels of HDL-c, which was associated with age, and triglycerides and hs-CRP levels. These findings should be considered in preventive programs for CVD (particularly atherosclerosis and its compications) in this population, aimed at changing lifestyle for improvement of metabolic and inflammatory profiles, and responses to inflammatory triggers inherent to their clinical condition. We suggest further multicentric studies with a prospective, longitudinal design, to test the prospective associations among HDL-c concentrations and atherosclerosis outcomes in children and adolescents with congenital heart disease.