The correlation between baroreflex sensitivity (BRS) and the spectrum component at a frequency of 0.1 Hz of pulse intervals (PI) and systolic blood pressure (SBP) was studied. SBP and PI of 51 subjects were recorded beat-to-beat at rest (3 min), during exercise (0.5 W/kg of body weight, 9 min), and at rest (6 min) after exercise. BRS was determined by a spectral method (a modified alpha index technique). The subjects were divided into groups according to the spectral amplitude of SBP at a frequency of 0.1 Hz. The following limits of amplitude (in mm Hg) were used: very high ≥ 5.4 (VH); high 5.4 > H ≥ 3 (H); medium 3 > M ≥ 2 (M), low < 2 (L). We analyzed the relationships between 0.1 Hz variability in PI and BRS at rest, during the exercise and during recovery in subgroups VH, H, M, L. The 0.1 Hz variability of PI increased significantly with increasing BRS in each of the groups with identical 0.1 Hz variability in SBP. This relationship was shifted to the lower values of PI variability at the same BRS with a decrease in SBP variability. The primary SBP variability increased during exercise. The interrelationship between the variability of SBP, PI and BRS was identical at rest and during exercise. A causal interrelationship between the 0.1 Hz variability of SBP and PI, and BRS was shown. During exercise, the increasing primary variability in SBP due to sympathetic activation was present, but it did not change the relationship between variability in pulse intervals and BRS., N. Honzíková, A. Krtička, Z. Nováková, E. Závodná., and Obsahuje bibliografii
The age-dependent changes in baroreflex control of heart rate were studied in inbred Dahl rats. At the age of 8 weeks the baroreflex slope was significantly greater in salt-resistant (R/Jr) than in salt-sensitive (S/Jr) rats fed a low- salt diet. The reverse was true in 16-week-old animals. High salt intake (8 % NaCI diet for 4 weeks) suppressed baroreflex efficiency in both age groups of S/Jr animals whereas no effects occurred in R/Jr rats. Baroreflex slope was, however, significantly lower in young S/Jr rats with a severe form of salt hypertension than in adult salt-loaded S/Jr rats in which only a moderate blood pressure elevation was observed.
Attention deficit/hyperactivity disorder (ADHD) is associated with complex neurocardiac integrity. We aimed to study heart rate time asymmetry as a nonlinear qualitative feature of heart rate variability indicating complexity of cardiac autonomic control at rest and in response to physiological stress (orthostasis) in children suffering from ADHD. Twenty boys with ADHD and 20 healthy age-matched boys at the age of 8 to 12 years were examined. The continuous ECG was recorded in a supine position and during postural change from lying to standing (orthostasis). Time irreversibility indices - Porta’s (P%), Guzik’s (G%) and Ehlers’ (E) - were evaluated. Our analysis showed significantly reduced heart rate asymmetry indices at rest (P%: 49.8 % vs. 52.2 %; G%: 50.2 % vs. 53.2 %; p<0.02), and in response to orthostatic load (P%: 52.4 % vs. 54.5 %, G%: 52.3 % vs. 54.5 %; p<0.05) associated with tachycardia in ADHD children compared to controls. Concluding, our study firstly revealed the altered heart rate asymmetry pattern in children suffering from ADHD at rest as well as in response to posture change from lying to standing (orthostasis). These findings might reflect an abnormal complex cardiac regulatory system as a potential mechanism leading to later cardiac adverse outcomes in ADHD., I. Tonhajzerová, I. Ondrejka, I. Farský, Z. Višňovcová, M. Mešťaník, M. Javorka, A. Jurko Jr., A. Čalkovská., and Obsahuje bibliografii
Baroreflex control of heart rate was studied in inbred salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) Dahl rats that were subjected to chronic dietary sodium chloride loading (for 4 weeks) either in youth or only in adulthood, i.e. from the age of 4 or 12 weeks. Using phenylephrine administration to pentobarbital-anesthetized male rats we have demonstrated the decreased baroreflex sensitivity (lower slope for reflex bradycardia) in young prehypertensive SS/Jr rats fed a low-salt diet as compared to age-matched SR/Jr animals. High salt intake further suppressed baroreflex sensitivity in young SS/Jr but not in SR/Jr rats. Baroreflex sensitivity decreased with age in SR/Jr rats, whereas it increased in SS/Jr rats fed a low-salt diet. Thus at the age of 16 weeks baroreflex sensitivity was much higher in SS/Jr than in SR/Jr animals. High salt intake lowered baroreflex sensitivity even in adult SS/Jr rats without affecting it in adult SR/Jr rats. Nevertheless, baroreflex sensitivity was significantly lower in young SS/Jr rats with a severe salt hypertension than in adult ones with a moderate blood pressure elevation. It is concluded that the alterations of baroreflex sensitivity in young inbred SS/Jr rats (including the response to high salt intake) are similar to those described earlier for outbred salt-sensitive Dahl rats. We have, however, disclosed contrasting age-dependent changes of baroreflex sensitivity in both inbred substrains of Dahl rats., J. Nedvídek, J. Zicha., and Obsahuje bibliografii
The aim of this study was to analyse the changes of baroreflex sensitivity (BRS) and their relation to changes of heart rate and blood pressure in medical students during moderate psychological stress brought about by oral examination. The changes of BRS during the stress were compared with the changes during light physical exercise. Thirty three students were examined 30 min before and 30 min after the exam. Thirty-nine students of control group were examined at rest and during light exercise. Blood pressure was noninvasively recorded by Peňáz method at rate-controlled breathing (0.33 Hz). The BRS [ms/mm Hg] and BRSf [Hz/mm Hg] were calculated by spectral analysis of spontaneous fluctuations of blood pressure and inter-beat intervals (IBI). BRS before examination (7.12 ms/mm Hg) was significantly lower than after the oral exam (8.77 ms/mm Hg, p<0.05). The difference between BRS in the test group after the oral exam and the control group at rest (10.78 ms/mm Hg) was not significant. BRS during light exercise (7.44 ms/mm Hg) corresponded to the value during psychological stress. The values of BRSf did not change during psychological stress (before: 0.0182 Hz/mm Hg; after: 0.0182 Hz/mm Hg) and exercise (rest: 0.0158 Hz/mm Hg; exercise: 0.0144 Hz/mm Hg). Correlation between BRS or BRSf and blood pressure were not found. A significant negative correlation (r = -0.404, p<0.05) between BRSf and the increase of diastolic blood pressure during stress was observed. It is concluded that BRSf remained constant during psychological stress and exercise, and differed essentially from that in hypertensive subjects.
Transgenic mice overexpressing a transthyretin promoter-ANF structural fusion gene have a life-long reduction in arterial blood pressure compared to nontransgenic littermates. The present study was designed to test the hypothesis that the high plasma level of ANF in the transgenic mice inhibits the renin-angiotensin and/or vasopressin systems, thereby causing the hypotension. Mice were anaesthetized with Inactin and arterial pressure and heart rate were monitored before and during Saralasin infusion and vasopressin Vi receptor blockade. Effectiveness of the blockade was determined by injection of angiotensin and vasopressin before and during Saralasin and V] receptor antagonist administration. Saralasin was associated with hypotension in both transgenic and nontransgenic mice. The decrease in blood pressure was proportionally greater in the transgenic animals. Vasopressin receptor blockade had little effect on blood pressure in either group. Heart rates were not different between the groups during any maneuver. We conclude that the chronic hypotensive effect of ANF overproduction does not involve the inhibition of either renin-angiotensin or vasopressin systems. The data, however, suggest that the renin-angiotensin system may be stimulated in the ANF-transgenic mice.
We studied the effects of the H2S donor Na2S on the mean arterial blood pressure (MAP) and heart and breathing rates of anesthetized Wistar rats in the presence and absence of captopril. Bolus administration of Na2S (1-4 μmol/kg) into the right jugular vein transiently decreased heart and increased breathing rates; at 8-30 μmol/kg, Na2S had a biphasic effect, transiently decreasing and increasing MAP, while transiently decreasing heart rate and increasing and decreasing breathing rate. These results may indicate independent mechanisms by which H2S influences MAP and heart and breathing rates. The effect of Na2S in decreasing MAP was less pronounced in the presence of captopril (2 μmol/l), which may indicate that the renin-angiotensin system is partially involved in the Na2S effect. Captopril decreased H2S-induced NO release from S-nitrosoglutathione, which may be related to some biological activities of H2S. These results contribute to the understanding of the effects of H2S on the cardiovascular system., M. Drobná, A. Misak, T. Holland, F. Kristek, M. Grman, L. Tomasova, A. Berenyiova, S. Cacanyiova, K. Ondrias., and Obsahuje bibliografii
Present study was aimed to investigate sympathetic responses to mental stress with hypothesis that the presence of obesity in patients with hypertension has a modifying effect. Young male subjects, 8 with hypertension grade I, with BMI<25 kg/m2 (HT), 10 with hypertension grade I, and BMI>30 kg/m2 (HT OB), 14 healthy controls with BMI<30 kg/m2 (OB), and 13 healthy controls with BMI<25 kg/m2 (C) underwent the Stroop test. ECG was recorded continuously to evaluate heart rate variability (HRV). Blood pressure (BP) and catecholamine concentrations were measured at baseline, at the end of mental stress test and 15 min thereafter. Patients with HT demonstrated increased adrenaline concentrations and enhanced stress-induced noradrenaline release compared to that in healthy controls. In obese subjects, stress-induced increase of systolicBP was lower compared to lean individuals. Stress exposure induced a significant rise in the low frequency power component of HRV, however the increase was lower in the HT OB group compared to C. Obesity in patients with hypertension did not lead to a different reaction in comparison with lean hypertensive subjects. The present data demonstrate higher sympathoadrenal activity in early-stage of hypertension. Obesity is connected with higher resting systolicBP and modifies the HRV response to mental stress., A. Garafova, A. Penesova, E. Cizmarova, A. Marko, M. Vlcek, D. Jezova., and Obsahuje bibliografii
Down Syndrome (Ds) is the most common chromosomal cause of intellectual disability that results from triplication of chromosome 21 genes. Individuals with Ds demonstrate cognitive deficits in addition to comorbidities including cardiac defects, pulmonary arterial hypertension (PAH), low blood pressure (BP), and differences in autonomic regulation. Many individuals with Ds are born with heart malformations and some can be surgically corrected. Lower BP at rest and in response to exercise and other stressors are a prevalent feature in Ds. These reduced cardiovascular responses may be due to underlying autonomic dysfunction and have been implicated in lower exercise/work capacity in Ds, which is an important correlate of morbidity, mortality and quality of life. Exercise therapy can be beneficial to normalize autonomic function and may help prevent the development of co-morbidities in Ds. We will review cardiovascular physiology and pathophysiology in individuals with Ds, along with exercise therapy and special considerations for these individuals.
The altered regulation of autonomic response to mental stress can result in increased cardiovascular risk. The laboratory tests used to simulate the autonomic responses to real-life stressors do not necessarily induce generalized sympathetic activation; therefore, the assessment of regulatory outputs to different effector organs could be important. We aimed to study the cardiovascular sympathetic arousal in response to different mental stressors (Stroop test, mental arithmetic test) in 20 healthy students. The conceivable sympathetic vascular index - spectral power of low frequency band of systolic arterial pressure variability (LF-SAP) and novel potential cardiosympathetic index - symbolic dynamics heart rate variability index 0V% were evaluated. The heart and vessels responded differently to mental stress - while Stroop test induced increase of both 0V% and LF-SAP indices suggesting complex sympathetic arousal, mental arithmetic test evoked only 0V% increase compared to baseline (p<0.01, p<0.001, p<0.01, respectively). Significantly greater reactivity of LF-SAP, 0V%, heart rate (HR) and mean arterial pressure (MAP) were found in response to Stroop test compared to mental arithmetic test potentially indicating the effect of different central processing (0V%, LF-SAP: p<0.001; HR, MAP: p<0.01). The different effectors’ sympathetic responses to cognitive stressors could provide novel important information regarding potential pathomechanisms of stress-related diseases., M. Mestanik, A. Mestanikova, Z. Visnovcova, A. Calkovska, I. Tonhajzerova., and Obsahuje bibliografii