To characterize the differences in baroreflex sensitivity (BRS), blood pressure (BP), heart rate (HR) and respiration rate (RR) in preterm infants with a similar postconceptional age reached by various combinations of gestational and postnatal ages. To detect potential sex differences in assessed cardiovascular parameters. The study included 49 children (24 boys and 25 girls), postconceptional age 34.6±1.9 weeks. Two subgroups of infants were selected with the similar postconceptional age (PcA) and current weight, but differing in gestational (GA) and postnatal (PnA) ages, as well as two matched subgroups of boys and girls. Blood pressure (BP) was recorded continuously using Portapres device (FMS). A stationary segment of 250 beat-to-beat BP values was analyzed for each child. Baroreflex sensitivity (BRS) was calculated by cross-correlation sequence method. Despite the same PcA age and current weight, children with longer GA had higher BRS, diastolic and mean BP than children with shorter GA and longer PnA age. Postconceptional age in preterm infants is a parameter of maturation better predicting baroreflex sensitivity and blood pressure values compared to postnatal age. Sex related differences in BRS, BP, HR and RR were not found in our group of preterm infants.
1a_It has been known for many years that baroreflex sensitivity is lowered in hypertensive patients. There are several known factors implicating this association, e.g. high blood pressure leads to remodeling of the carotid arterial wall, to its stiffness and to a diminished activation of baroreceptors; leptin released from a fatty tissue activates the sympathetic nervous system etc. On the other hand, low baroreflex sensitivity (BRS, usually quantified in ms/mmHg) can be inborn. Studies on primary hypertension in children and adolescents have brought new information about the role of baroreflex in the development of an early stage of primary hypertension. BRS lower than 3.9 ms/mmHg was found in 5 % of healthy subjects. This value approaches the critical value for the risk of sudden cardiac death in patients after myocardial infarction and corresponds to the value present in hypertensive patients. A decreased BRS and BRSf (baroreflex sensitivity expressed in mHz/mmHg, index independent of the mean cardiac interval), was found not only in children with hypertension, but also in those with white-coat hypertension. This is in accordance with a single interpretation. The decrease of BRS/BRSf precedes a pathological blood pressure increase., 2a_The contribution of obesity and BRS/BRSf to the development of hypertension in adolescents was also compared. Both factors reach a sensitivity and a specificity between 60 % and 65 %, but there is no correlation between the values of the body mass index and BRS either in the group of hypertensive patients or in healthy controls. If a receiver operating curve (sensitivity versus specificity) is plotted for both values together using logistic regression analysis, a sensitivity higher than 70 % and a specificity over 80 % are reached. This means that low baroreflex sensitivity is an independent risk factor for the development of primary hypertension. Studies demonstrate that adolescents with increased blood pressure and with BRS under 7 ms/mmHg should be given care and intensively motivated to change their lifestyle including a change in diet and increase in physical activity., and N. Honzíková, B. Fišer.
The reproducibility of baroreflex sensitivity (BRS in ms/mmHg; BRSf in mHz/mmHg) determined with respect to the coherence between the variability in systolic blood pressure (SBP) and inter-beat intervals (IBI) or heart rate (HR) was tested. SBP and IBI were recorded beat-to-beat for 5 min (Finapres, breathing at 0.33 Hz) in 116 subjects (aged 19-24 years) sitting at rest three times in periods of one week. BRS and BRSf was determined by a cross-spectral method in a frequency range of 0.067-0.133 Hz. Eight indices were evaluated: BRS0.1Hz/BRSf0.1Hz - the value at a frequency of 0.1 Hz; BRSCOHmax/BRSfCOHmax - the value at maximum coherence; BRSWcoh/BRSfWcoh - weighted value with respect to coherence values in the whole frequency range; BRSWPcoh/BRSWPcoh - weighted value with respect to coherence for frequencies with coherence above 0.5. All indices revealed a lower intraindividual than interindividual variability (p<0.001). The individual mean values of BRS or BRSf correlated (p<0.001) with standard deviation of their individual values for all indices. Baroreflex sensitivity is an individual characteristic feature with the highest reproducibility at its low values in spite of its resting variation. Reproducibility is not influenced by modification of the spectral method used.
Sympathetic overactivity and low parasympathetic activity is an autonomic dysfunction (AD) which enhances cardiac mortality. In the present study, the impact of AD on the mortality in patients after myocardial infarction was evaluated. We examined 162 patients 7-21 days after myocardial infarction, 20 patients of whom died in the course of two years. Baroreflex sensitivity (BRS) was estimated by spectral analysis of spontaneous fluctuations of systolic blood pressure and cardiac intervals (Finapres, 5 min recording, controlled breathing 20/min). The heart rate variability was determined as SDNN index (mean of standard deviations of RR intervals for all 5-min segments of 24-hour ECG recordings). BRS < 3 ms/mm Hg and/or SDNN index < 30 ms were taken as markers of AD. The risk stratification was performed according to the number of the following standard risk factors of increased risk of cardiac mortality (SRF): ejection fraction < 40 %, positive late potentials and the presence of ventricular extrasystoles > 10/h. No difference in mortality between patients with AD (4 %) and without AD (4.5 %) was found in 92 patients without SRF, the mortality in 6 patients with three SRF was 66.6 %. Five of these patients had AD. Out of 64 patients with one or two SRF, 32 had AD. The mortality of patients without AD was 6.25 % and 31.2 % of those with AD (p<0.025). It is concluded that AD enhanced two-years mortality five fold in our patients with moderate risks., N. Honzíková, B. Semrád, B. Fišer, R. Lábrová., 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.
Roads and highways represent one of the most important anthropogenic impacts on natural areas and contribute to habitat fragmentation, because they are linear features that can inhibit animal movement, thereby causing barrier effects by subdividing the populations adjacent to the roads. The study presented here aims to determine, to which extent roads act as a barrier, subdividing populations of three species of small forest mammals: bank vole, yellow-necked mouse and common shrew, and what is the relative importance of road width and traffic intensity on the barrier effect. The study was carried out at four 25 m long segments of roads, close to the city of České Budějovice. All segments crossed a forest. The capture-recapture method was applied to determine the crossing rates of animals. The traps were checked three times each day during four consecutive nights, in summer and in autumn. We found that: (1) roads strongly prevent crossing movements in all three studied species, (2) there are interspecific differences in road crossing rates, (3) species cross more often narrow than wide roads, (4) traffic intensity does not affect the crossing rates.
Fleas (95 Pulex irritans, 50 Ctenocephalides felis, 45 Ctenocephalides canis) and ixodid ticks (223 Ixodes ricinus, 231 Dermacentor reticulatus, 204 Haemaphysalis concinna) were collected in Hungary and tested, in assays based on PCR, for Bartonella infection. Low percentages of P. irritans (4.2%) and C. felis (4.0%) were found to be infected. The groEL sequences of the four isolates from P. irritans were different from all the homologous sequences for bartonellae previously stored in GenBank but closest to those of Bartonella sp. SE-Bart-B (sharing 96% identities). The groEL sequences of the two isolates from C. felis were identical with those of the causative agents of cat scratch disease, Bartonella henselae and Bartonella clarridgeiae, respectively. The pap31 sequences of B. henselae amplified from Hungarian fleas were identical with that of Marseille strain. No Bartonella-specific amplification products were detected in C. canis, I. ricinus, D. reticulatus and H. concinna pools.