title: Subclinical myocardial dysfunction and cardiac autonomic dysregulation are closely associated in obese children and adolescents: the potential role of insulin resistance.
abstract: BACKGROUND
  The prevalence of obesity is increasing among children/adolescents. Subtle cardiovascular abnormalities, responsible for a higher mortality later in life, have been reported in obese children/adolescents. The aims of the study were to evaluate cardiovascular autonomic regulation, by means of spectrum analysis of R-R interval variability, and myocardial function, by means of standard and tissue Doppler echocardiography, in a group of non-hypertensive asymptomatic obese children and adolescents; furthermore, the influence of insulin resistance was tested.
  
  
  METHODS
  R-R interval variability was analyzed during both the 70° head-up tilt and 24-hour electrocardiographic holter monitoring. Spectrum analysis of R-R interval variability provided the indices of sympathetic (low frequency [LFRR]) and vagal (high frequency [HFRR]) modulation of the sinoatrial node. Homeostasis model assessment of insulin resistance (HOMA-IR) was used to classify obese children/adolescents (n=72) as insulin resistant (n=37) and non-insulin resistant (n=35).
  
  
  RESULTS
  In obese subjects: a) left ventricular mass was significantly (p<0.05) increased, whereas both the e/a ratio and the e'/a' ratio were decreased; b) at rest, HFRR was lower, and the LFRR/HFRR ratio was higher; c) during tilting, magnitude of tilt-induced inhibition of HFRR was lower; d) during 24-hour electrocardiographic holter monitoring, LFRR and the LFRR/HFRR ratio were higher, whereas HFRR was lower; e) HOMA-IR inversely correlated with both the e'/a' ratio (r=-0.655; p<0.001) and the tilt-induced LFRR/HFRR ratio (r=-0.933; p<0.001); and, f) the e'/a' ratio correlated with the tilt-induced LFRR/HFRR ratio (r=0.501; p<0.001). Moreover, HFRR at rest, magnitude of tilt-induced HFRR reduction, and the e'/a' ratio in insulin resistant obese children/adolescents were markedly lower when compared with the remaining subjects.
  
  
  CONCLUSIONS
  Subclinical abnormalities of myocardial function and of cardiac autonomic regulation were closely associated in obese children/adolescents and both correlated with the degree of insulin resistance.
authors.affiliation: Department of Internal Medicine, Second University of Naples, Naples, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Cozzolino
authors.affiliation: Department of Women, Child and General and Specialized Surgery, Second University of Naples, Naples, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Grandone
authors.affiliation: Department of Translational Medical Sciences, Federico II University, Naples, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cittadini
authors.affiliation: Department of Internal Medicine, Second University of Naples, Naples, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Palmiero
authors.affiliation: Department of Advanced Biomedical Sciences, Federico II University, Naples, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Esposito
authors.affiliation: Department of Cardiothoracic and Respiratory Sciences, Second University of Naples, Naples, Italy.
authors.forename: Annamaria
authors.initials: A
authors.lastname: De Bellis
authors.affiliation: Internal Medicine, Humanitas Research Hospital, University of Milan, Rozzano, Italy.
authors.forename: Raffaello
authors.initials: R
authors.lastname: Furlan
authors.affiliation: Department of Women, Child and General and Specialized Surgery, Second University of Naples, Naples, Italy.
authors.forename: Silverio
authors.initials: S
authors.lastname: Perrotta
authors.affiliation: Department of Women, Child and General and Specialized Surgery, Second University of Naples, Naples, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Perrone
authors.affiliation: Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Torella
authors.affiliation: Department of Women, Child and General and Specialized Surgery, Second University of Naples, Naples, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Miraglia Del Giudice
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D009765:Obesity / Q000503:physiopathology*