Elsevier

Sleep Medicine

Volume 11, Issue 4, April 2010, Pages 406-412
Sleep Medicine

Original Article
Cardiac systolic function in Greek children with obstructive sleep-disordered breathing

https://doi.org/10.1016/j.sleep.2009.05.019Get rights and content

Abstract

Background

Obstructive sleep-disordered breathing (SDB) in children has been associated with increased ventricular strain and decreased left ventricle (LV) diastolic function. The aim of this study was to assess systolic myocardial function in children with SDB of variable severity.

Methods

Children who were referred for polysomnography during the study period underwent echocardiography (two-dimensional, Doppler and tissue Doppler imaging).

Results

A total of 46 subjects (age 6.4 ± 2.6 years) were recruited. Fourteen of them had moderate-to-severe SDB (obstructive apnea-hypopnea index (OAHI): 16.6 ± 11.6 episodes/h), 13 children had mild SDB (OAHI: 3.1 ± 0.7 episodes/h) and 19 subjects had primary snoring (OAHI: 1.2 ± 0.6 episodes/h). Children with moderate-to-severe SDB had significantly lower LV shortening fraction (SF) and ejection fraction (EF) than subjects with primary snoring (p < 0.05). SF in moderate-to-severe SDB, mild SDB and primary snoring groups was: 34.3 ± 5.5%, 36.9 ± 3.2% and 37.7 ± 4.4%, respectively, and EF: 66.9 ± 7.9%, 71.7 ± 6.4% and 72.3 ± 5.9%, respectively. OAHI, age, and systolic blood pressure were significant predictors of SF and EF (p < 0.01).

Conclusions

In children with obstructive SDB, LV systolic function is inversely associated with severity of intermittent upper airway obstruction during sleep.

Introduction

Accumulating evidence indicates that severity of obstructive sleep-disordered breathing (SDB) in childhood correlates with surrogate measures of future cardiovascular morbidity [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. Elevated serum concentrations of C-reactive protein (CRP) have been demonstrated in subgroups of children with sleep apnea [2], [11], and increased fasting insulin levels have been found mostly in obese children with SDB [12], [13], [14]. Moreover, a significant association has been identified between the metabolic syndrome and sleep apnea in children and adolescents [3], [9]. Treatment of intermittent upper airway obstruction during sleep with adenotonsillectomy is accompanied by improved lipid profile and endothelial function and reduced CRP levels [1], [4].

In addition, several studies have revealed that obstructive SDB is associated with blood pressure elevation [5], [10], [15] and changes in myocardial structure and function [7], [8], [16], [17]. Children with snoring and apnea-hypopnea index > 5 episodes/h have significantly higher wake systolic and wake and sleep diastolic blood pressure compared to healthy controls [5], and successful treatment of upper airway obstruction by adenotonsillectomy seems to decrease mainly the diastolic component of blood pressure [2], [6], [18]. Subjects with severe sleep apnea can present with pulmonary hypertension [19] and decreased right ventricle systolic function [16], [17]. A recent echocardiography study has identified increased right ventricle end-diastolic dimension and left ventricle mass index [7]. Finally, a negative correlation has been reported between severity of obstructive SDB and left ventricle (LV) diastolic function [8], which improves after surgical removal of adenoids and tonsils [20].

In contrast to older reports [16], [17], recent echocardiography studies have not detected a negative impact of sleep apnea on systolic myocardial function [8], [20]. Children with obstructive SDB, however, have increased blood and urine norepinephrine levels [21], [22], and, at least in adults with sleep apnea, increased release of catecholamines has been associated with decreased sensitivity of β-adrenergic receptors [23]. Desensitization of the β-adrenergic receptors may conceivably lead to isolated reduced systolic function even without the presence of diastolic dysfunction or cardiac structure abnormalities. Therefore, we performed an exploratory study to assess cardiac systolic function in children with moderate-to-severe SDB in comparison to subjects with mild SDB or with primary snoring.

Section snippets

Participants

The study protocol was approved by the University of Thessaly Ethics Committee. Informed consent was obtained from parents of participants and child’s assent from subjects older than 6 years. Consecutive children with snoring (>3 nights/week) who were referred to the Sleep Disorders Laboratory for polysomnography were offered the chance to participate in the study if they did not have (1) symptoms of upper respiratory tract infection; (2) history of cardiovascular, neuromuscular or genetic

Subjects’ characteristics and polysomnography findings

A total of 48 children who had polysomnography at the sleep lab were recruited to the study and underwent echocardiography (age range of 2.3–12.2 years). Two of them were excluded due to patent ductus arteriosus that was diagnosed during echocardiography. Thus, data collected from 46 subjects (22 female; 47.8%) with a mean age of 6.4 ± 2.6 years were analyzed. Their characteristics and polysomnography findings are summarized in Table 1.

Primary outcome measures: indices of systolic ventricular function

The three study groups were similar regarding right ventricle

Discussion

The main finding of the current investigation is the lower LV systolic function in children with moderate-to-severe SDB compared to subjects with primary snoring. This result is in agreement with older pediatric reports that have identified an increase of the right and left ventricle EF after adenotonsillectomy for obstructive sleep apnea [16], [17]. Although the size of the current cohort is modest, the findings add to the scarce literature on the topic and could be utilized in future

Conflict of interest

None of the authors has any conflicts of interest to disclose.

Acknowledgement

Funded by the University of Thessaly Research Committee.

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