title: Symbolic dynamics of heart rate variability - a promising tool to investigate cardiac sympathovagal control in attention deficit/hyperactivity disorder (ADHD)?
abstract: We aimed to evaluate complex cardiac sympathovagal control in attention deficit/hyperactivity disorder (ADHD) by using heart rate variability (HRV) nonlinear analysis - symbolic dynamics. We examined 29 boys with untreated ADHD and 25 healthy boys (age 8-13 years). ADHD symptoms were evaluated by ADHD-RS-IV scale. ECG was recorded in 3 positions: baseline supine position, orthostasis, and clinostasis. Symbolic dynamics indices were used for the assessment of complex cardiac sympathovagal regulation: normalised complexity index (NCI), normalised unpredictability index (NUPI), and pattern classification measures (0V%, 1V%, 2LV%, 2UV%). The results showed that HRV complexity was significantly reduced at rest (NUPI) and during standing position (NCI, NUPI) in ADHD group compared to controls. Cardiac-linked sympathetic index 0V% was significantly higher during all posture positions and cardiovagal index 2LV% was significantly lower to standing in boys suffering from ADHD. Importantly, ADHD symptom inattention positively correlated with 0V%, and negatively correlated with NCI, NUPI. Concluding, symbolic dynamics revealed impaired complex neurocardiac control characterised by potential cardiac beta-adrenergic overactivity and vagal deficiency at rest and to posture changes in boys suffering from ADHD that is correlated with inattention. We suggest that symbolic dynamics indices could represent promising cardiac biomarkers in ADHD.
authors.affiliation: a Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Department of Physiology JFM CU and Biomedical Center Martin JFM CU, Mala Hora 4C, 03601 Martin, Slovak Republic.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Tonhajzerova
authors.affiliation: b Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Clinic of Psychiatry JFM CU, University Hospital Martin, Kollarova 2 and Department of Nursing JFM CU, Mala Hora 5, 03601 Martin, Slovak Republic.
authors.forename: Ivan
authors.initials: I
authors.lastname: Farsky
authors.affiliation: a Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Department of Physiology JFM CU and Biomedical Center Martin JFM CU, Mala Hora 4C, 03601 Martin, Slovak Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Mestanik
authors.affiliation: a Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Department of Physiology JFM CU and Biomedical Center Martin JFM CU, Mala Hora 4C, 03601 Martin, Slovak Republic.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Visnovcova
authors.affiliation: a Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Department of Physiology JFM CU and Biomedical Center Martin JFM CU, Mala Hora 4C, 03601 Martin, Slovak Republic.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mestanikova
authors.affiliation: c Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Clinic of Psychiatry JFM CU and University Hospital Martin, Kollarova 2, 03601 Martin, Slovak Republic.
authors.forename: Igor
authors.initials: I
authors.lastname: Hrtanek
authors.affiliation: c Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin (JFM CU), Clinic of Psychiatry JFM CU and University Hospital Martin, Kollarova 2, 03601 Martin, Slovak Republic.
authors.forename: Igor
authors.initials: I
authors.lastname: Ondrejka
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000503:physiopathology*; D002648:Child; D004562:Electrocardiography / Q000379:methods; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014630:Vagus Nerve / Q000503:physiopathology*
keywords: ADHD; TDAH; cardiac sympathovagal regulation; complexity; complexité; dynamique symbolique; heart rate variability; inattention; orthostasis; orthostatisme; régulation sympathovagale cardiaque; symbolic dynamics; variabilité de la fréquence cardiaque