Andrea Mestanikova

The complexity of electrodermal activity is altered in mental cognitive stressors

The aim of this study was to evaluate potential changes in the electrodermal activity (EDA) to enable the detection of variations in the sympathetic nervous system during mental load and recovery period. Several EDA parameters were used: SCA (skin conductance amplitude), frequency of NS-EDR (nonspecific electrodermal responses), SIE (symbolic information entropy), and ApEn (approximate entropy). The cohort consisted of 50 healthy students (average age: 23.33±0.24yr., 25 women). The stress profile consisted of five phases: baseline (P1), Stroop test (P2), recovery (P3), mental arithmetic test (P4), and recovery (P5). All phases of the stress profile lasted six minutes. The results indicate that the three EDA indices have sufficient sensitivity to detect changes in the sympathetic nervous system. The SCA, SIE and ApEn were significantly increased during mental loads and decreased during recovery periods. However, SCA remained significantly elevated during recovery periods versus baseline, and SIE and ApEn decreased significantly during recovery versus baseline. The frequency of NS-EDR had no significant changes during stress. The EDA is a sensitive marker for evaluation of changes during the activation of sympathetic nervous system under the influence of a load. Detailed knowledge of EDA regulatory mechanisms associated with stress could provide important information associated with autonomic dysregulation.

Arterial stiffness evaluated by cardio-ankle vascular index (CAVI) in adolescent hypertension

Elevated blood pressure (BP) is a major risk factor for atherosclerosis. As the studies concerning vascular alterations in pediatric patients are rare, we aimed to study the relationship between hypertension and arterial stiffness in adolescence by novel method independent from BP during examination. Twenty nonobese adolescent boys (16.5 ± 0.4 years) with newly diagnosed essential hypertension, 20 adolescent boys (16.7 ± 0.4 years) with newly diagnosed white-coat hypertension, and 20 healthy controls matched to age and body mass index were examined. Cardio-ankle vascular index (CAVI), brachial-ankle pulse wave velocity (baPWV), pre-ejection period (PEP), and ejection time (ET) were evaluated. CAVI was significantly increased in essential hypertension patients compared with controls (p < 0.05) with no significant difference in white-coat hypertension patients. Significantly higher baPWV was found in essential and white-coat hypertension patients compared with controls (both p < 0.001). White-coat hypertension patients showed significantly shortened PEP and ET compared with controls (p < 0.01 and p < 0.001, respectively) and essential hypertension patients (both p < 0.05). For the first time, the arterial stiffness in adolescents with newly diagnosed essential and white-coat hypertension was studied using BP-independent index CAVI combined with conventional baPWV. Our study revealed significantly increased CAVI in adolescents with newly diagnosed essential hypertension compared with controls. Our findings could help to understand hypertension-atherosclerosis interaction.

Symbolic dynamics of heart rate variability — a promising tool to investigate cardiac sympathovagal control in attention deficit/hyperactivity disorder (ADHD)?

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.

Respiratory sinus arrhythmia – testing the method of choice for evaluation of cardiovagal regulation

Respiratory sinus arrhythmia (RSA) is an index of cardiovagal regulation, emotional and cognitive processing. RSA is quantified using heart rate variability (HRV) spectral analysis at respiratory-linked high-frequency band (HF-HRV) using Fast Fourier transformation (FFT) or autoregressive (AR) method, both requiring resampling of recordings - a potential source of error. We hypothesized that rarely used HRV time-frequency analysis with Lomb-Scargle periodogram (LSP) without resampling could be more sensitive to detect neurocardiac response to posture change than FFT and AR. Orthostasis (posture change from supine to standing) evoked significant decrease of HF-HRV well detectable by FFT, AR, and LSP. In contrast, during posture change from sitting to lying, significant increase of HF-HRV and peak HF was best detected using LSP. In regression analysis, the associations between RR-interval, HF-HRV, and peak HF were best detected when evaluated using LSP. Time-frequency HRV analysis with LSP could represent an important alternative to conventional FFT and AR methods for assessment of cardiovagal regulation indexed by RSA.

Improved assessment of arterial stiffness using corrected cardio-ankle vascular index (CAVI0) in overweight adolescents with white-coat and essential hypertension

Abstract Arterial stiffness is a marker of vascular damage. Although adiposity increases cardiovascular risk, the relationship between paediatric overweight and arterial stiffness is unclear. The study aimed to evaluate the simultaneous effect of hypertension and overweight on arterial stiffness using cardio-ankle vascular index (CAVI) and related novel, theoretically blood pressure (BP)-independent, index CAVI0. CAVI and CAVI0 were measured in 140 adolescent boys (16.0 ± 1.9 years) divided into age-matched groups: normal-weight normotensives, overweight normotensives, overweight white-coat hypertensives, and overweight essential hypertensives. Overweight normotensives had significantly lower CAVI and CAVI0 compared to normal-weight normotensives (4.81 ± 0.64 vs. 5.33 ± 0.66, p < .01; 7.10 ± 0.99 vs. 7.81 ± 1.00, p < .01, respectively). CAVI and CAVI0 in overweight essential hypertensives showed no significant difference compared to normal-weight normotensives and were significantly higher compared to overweight normotensives (5.32 ± 0.77 vs. 4.81 ± 0.64, p < .01; 7.77 ± 1.19 vs. 7.10 ± 0.99, p < .01, respectively). CAVI, but not CAVI0, was associated positively with diastolic pressure (0.022 mmHg−1, p = .002) and negatively with pulse pressure (−0.022 mmHg−1, p = .001), and it was significantly higher in overweight white-coat hypertensives compared to overweight normotensives (5.20 ± 0.63 vs. 4.81 ± 0.64, p < .05). The lowering effect of overweight on arterial stiffness indexed by CAVI and CAVI0 in hypertensive adolescents seems to counterbalance the early arteriosclerotic effect of essential hypertension. The increase in CAVI, but not CAVI0, in overweight white-coat hypertensives could be attributable to residual BP dependence of CAVI, which is not present in CAVI0. Under certain conditions, CAVI0 may offer a clinically relevant improved assessment of arterial stiffness superior to CAVI.

Respiratory sinus arrhythmia as a non-invasive index of 'brain-heart' interaction in stress

Respiratory sinus arrhythmia (RSA) is accepted as a peripheral marker of cardiac-linked parasympathetic regulation. According to polyvagal theory, the RSA is also considered as the index of emotion regulation. The neurovisceral integration model posits that parasympathetic modulation of the heart marked by RSA is related to complex nervous regulation associated with emotional and cognitive processing. From this perspective, high resting RSA amplitude associated with a greater withdrawal during stressors and subsequent recovery could represent a flexible and adaptive physiological response system to a challenge. Conversely, low resting RSA accompanied by an inadequate reactivity to stress might reflect maladaptive regulatory mechanisms. The RSA reactivity is different with various types of stressors: while the RSA decreases to cognitive tasks indicating a vagal withdrawal, the RSA magnitude increases to emotional challenge indicating an effective cognitive processing of emotional stimuli. The RSA reactivity to stress could have important implications for several mental disorders, e.g. depressive or anxiety disorder. It seems that the study of the RSA, as a non-invasive index of ‘brain-heart’ communication, could provide important information on the pathway linked to mental and physical health.

Cardiac Vagal Control and Depressive Symptoms in Response to Negative Emotional Stress

We aimed to study complex cardiovagal control using heart rate variability (HRV), linear and nonlinear analyses at rest and during negative emotional stress in healthy students with varying depressive symptoms. ECG recording in 20 students was performed at baseline, negative emotional stress, and recovery period. The HRV parameters evaluated were the following: RR interval, spectral power in high-frequency band (HF-HRV), and symbolic dynamics index 2LV%. The subjects were divided into two groups based on the score of the Beck Depression Inventory (BDI) - normal mood (BDI: 0.6 ± 0.2) and mild mood disturbance (BDI: 14.3 ± 1.4). We found significantly lower logHF-HRV during emotional stress in mild mood disturbance compared with normal mood (p = 0.047). No significant differences were found in the remaining parameters. We conclude that negative emotional stress attenuated the cardiovagal control during mood disturbance, which points to discrete abnormalities in the neurocardiac reflex system associated with depressive symptoms. Hampered cardiovagal control could represent a potential pathomechanism leading to depression-linked cardiovascular complications.