Impact of body fat mass extent on cardiac autonomic alterations in women

Background  Obesity has been associated with significant abnormalities of the cardiac autonomic regulation. However, the precise impact of increasing body weight on cardiac autonomic function and the metabolic and hormonal contributors to these changes are presently unclear. The aim of our study was to explore in subjects with increasing values of body mass index (BMI) the alterations of cardiac autonomic function and to establish the potential role of various metabolic and hormonal contributors to these alterations.
Materials and methods  We investigated time and frequency domain heart rate variability (HRV) parameters taken from 24-h Holter recordings, and several anthropometric, metabolic and hormonal parameters (plasma glucose, insulin, triglycerides, free fatty acids, leptin and adiponectin) in 68 normoglycaemic and normotensive women (mean age of 40 ± 3 years), subdivided according to their BMI into 15 normal body weight (controls), 15 overweight, 18 obese and 20 morbidly obese.
Results  Heart rate was increased and HRV was decreased in the morbidly obese group as compared with controls. In overall population, a negative association linked body fat mass (FM) to HRV indices. None of the metabolic and hormonal parameters were significantly related to the HRV indices, after they were adjusted for the body FM.
Conclusions  Morbidly obese, normoglycaemic and normotensive young women have increased HR and low HRV, indicating an abnormal cardiac autonomic function and representing a risk factor for adverse cardiovascular events. A decrease of HRV parameters is associated with a progressive increase of body FM. Other metabolic and hormonal factors, characterising obesity, do not show an independent influence on these HRV alterations.     

Fetal development: voice processing in normotensive and hypertensive pregnancies

Recent observation of maternal voice recognition provides evidence of rudimentary memory and learning in healthy term fetuses. However, such higher order auditory processing has not been examined in the presence of maternal hypertension, which is associated with reduced and/or impaired uteroplacental blood flow. In this study, voice processing was examined in 40 fetuses (gestational ages of 33 to 41 weeks) of hypertensive and normotensive women. Fetuses received 2 min of no sound, 2 min of a tape-recorded story read by their mothers or by a female stranger, and 2 min of no sound while fetal heart rate was recorded. Results demonstrated that fetuses in the normotensive group had heart rate accelerations during the playing of their mother's voice, whereas the response occurred in the hypertensive group following maternal voice offset. Across all fetuses, a greater fetal heart rate change was observed when the amniotic fluid index was above compared to below the median (i.e., 150 mm), indicating that amniotic fluid volume may be an independent moderator of fetal auditory sensitivity. It was concluded that differential fetal responding to the mother's voice in pregnancies complicated by maternal hypertension may reflect functional elevation of sensorineural threshold or a delay in auditory system maturation, signifying functional differences during fetal life or subtle differences in the development of the central nervous system.     

Effects of mental state on heart rate and blood pressure variability in men and women

Summary. The effect of different mental states on autonomic modulation of the cardiovascular system was assessed in healthy, normotensive men (n=18) and women (n=12). Heart rate variability (HRV), systolic blood pressure variability (BPV) and arterial baroreflex function were assessed during 4 tests at rest ((10 min+5 min recovery)×4):

• 1 Control (spontaneous breathing, (SB)
• 2 Mental distraction (SB+word puzzle)
• 3 Conscious control of breathing (paced at SB rate) and
• 4 Mental stress (SB+computer quiz).

There were no significant gender differences in the responses to the interventions in terms of arterial (spontaneous) baroreflex (SPBX) control of HR, and indices of time and frequency domains of HRV and BPV, with the exception of the sympathetic indicator of HRV (low frequency power/total power; P<0.01) which was lower in women during control and mental stress tests. Conscious control of breathing at SB did not alter HRV, BPV or SPBX in either men or women. Mental distraction and mental stress led to decreases in indices of time and frequency domains of HRV and BPV in all subjects, as well as increases in HR during distraction and in systolic BP during stress. These findings suggest that in studies of cardiovascular control:

• 1 Paced breathing at SB can be used for individuals with irregular breathing patterns
• 2 The extent of mental stress achieved is intervention-specific and for the most part, independent of gender and
• 3 Resting assessment of HRV, BPV and SPBX can be made by having subjects sit quietly without interventions in a controlled laboratory setting.

     

Short- and long-term reproducibility of autonomic measures in supine and standing positions

Autonomic nervous tests and heart rate variability (HRV) have been used to assess cardiac autonomic function and to evaluate long-term prognosis. The aim of this study was to evaluate the short- and long-term reproducibility of HRV parameters and autonomic nervous tests according to body position (supine or standing). The study group consisted of 26 healthy subjects. Autonomic nervous tests and HRV were performed twice during the day and the results were averaged. The protocol was then repeated 3 days after each examination and also after 6 and 24 months. Autonomic nervous tests included deep breathing, Valsalva manoeuvre and isometric muscle exercise (handgrip), as well as blood pressure and heart rate in response to standing. ECG recordings were taken for 10 min during spontaneous breathing for HRV analysis. We found that the reproducibility of some parameters of the autonomic nervous test were independent of body position [E/I ratio (heart rate response to deep breathing)], whereas other parameters were dependent on body position (Valsalva manoeuvre and blood pressure response to sustained handgrip). In addition, within-day measurements of those parameters varied from non-reproducible (Valsalva ratio, handgrip and blood pressure response to standing) to moderately reproducible [E/I ratio and 30/15 ratio (heart rate response to standing)]. Among the HRV parameters, we found that total power (TP), low (LF)- and high (HF)-frequency were reproducible not only for measurements made within the same day, but also during short- and long-term observations, and only the LF/HF ratio was dependent on body position. We conclude that only a few autonomic nervous tests are reproducible in the short- and long-term. Because HRV parameters obtained during spontaneous respiration showed high reproducibility for measurements made within the same day as well as in the short- and long-term, they should be used instead of autonomic nervous tests when long-term observations are carried out in a healthy population.     

Ramipril Enhances Autonomic Control in Essential Hypertension: A Study Employing Spectral Analysis of Heart Rate Variation

We estimated the effect of an angiotensin-converting enzyme inhibitor, ramipril, on the sympathetic and parasympathetic input to the sinoatrial node of hypertensive patients using spectral and time domain analysis of heart rate variation (HRV). The heart rate of patients with essential hypertension was recorded during spontaneous breathing at rest and during controlled deep breathing. The periodic HRV was quantified at low-frequency (0.025--0.075 Hz), mid-frequency (0.075--0.125 Hz) and high-frequency (0.15--0.40 Hz) bands. Ramipril changed the balance of autonomic nervous system assessed by spectra: the parasympathetic tone increased (p < 0.05) and the sympathetic tone decreased (p < 0.01). There was an inverse correlation between the decrease in diastolic blood pressure and increase in the mid-frequency HRV, which is connoted with resetting of the baroreceptor reflex by ramipril. Thus, ramipril treatment was associated with improved autonomic control of the circulatory system.     

Factors influencing heart rate variability power spectral analysis during controlled breathing in patients with chronic heart failure or hypertension and in healthy normotensive subjects

A decreased LFP (low-frequency power) spectral component of HRV [HR (heart rate) variability] is a risk factor for sudden death in patients with CHF (chronic heart failure). In the present study, we evaluated factors (age, arterial pressures and HR) influencing LFP and HFP (high-frequency power) components in short-term recordings during controlled breathing in patients with CHF or hypertension, and healthy normotensive subjects. In patients with CHF, we also compared LFP values with known markers of sudden death [NYHA (New York Heart Association) class, HR and ejection fraction]. All HRV measures were significantly lower in patients with CHF than in hypertensive and normotensive subjects (P<0.001), and in hypertensive than in normotensive subjects (P<0.05). Stepwise multiple regression analysis showed that, in patients with CHF, LFP was inversely associated with NYHA class (beta=-0.5, P<0.0001) and HR (beta=-0.2, P=0.001) and was positively associated with ejection fraction (beta=0.28, P<0.0001). In patients with CHF, LFP remained unchanged with age. In normotensive and hypertensive subjects, HFP decreased with age, but in patients with CHF it did not. In the >/=60<70 and >/=70 years of age subgroups, we found no difference between HFP in the three groups studied. Hence, in normotensives and hypertensives, LFP tended to diminish with age (beta=-0.4, P<0.0001 in normotensives; beta=-0.4, P<0.001 in hypertensives) and was inversely associated with HR (beta=-0.2, P=0.002 in normotensives; beta=-0.3, P=0.002 in hypertensives). Conversely, in patients with CHF, LFP is predominantly influenced by NYHA class, HR and ejection fraction, but not by age. LFP might therefore increase the sensitivity of factors already used in stratifying the risk of sudden death in patients with CHF.     

Reactivity of autonomic nervous control of heart rate in diabetes mellitus and juvenile rheumatoid arthritis

Autonomic cardiac control of children with diabetes mellitus (DM, n = 12), juvenile rheumatoid arthritis (JRA, n = 12) and healthy controls (n = 12) was studied by a procedure consisting of a deep breathing test and an intermittent tilting test. Frequency selective entrainment of HR could be produced by tilting and deep breathing. No statistically significant intergroup differences were detected in the patterns of average heart rate (HR), overall or beat-to-beat heart rate variability (HRV) or HRV spectra. The DM group had an 8% higher HR and a limited short-term HRV response in relation to HR throughout the whole test procedure compared to controls. This increased HR causes an extra load to the cardiovascular system. We conclude that in spite of elevated HR and changed short-term chronotropic HR control in DM no features of autonomic failure could be detected in children with JRA.     

超声评估妊娠期高血压疾病对晚孕期母胎心功能及胎儿生长发育的影响

目的使用超声参数较为全面、系统的评估妊娠期高血压疾病母胎心功能及胎儿生长发育,为母胎一体化管理提供有价值的信息。方法选取孕周28～41+6周的孕妇150例,妊娠期高血压疾病孕妇60例为疾病组,与其孕龄匹配且血压正常的孕妇90例为对照组。测量的超声参数:(1)孕妇LVDd、LAD、IVSTd、LVPWTd、LVEF、二尖瓣环运动速度的Ea/Aa值。(2)胎儿右心室Tei指数。(3)胎儿BPD、HC、AC、FL。结果疾病组孕妇LVDd、LAD、IVSTd、LVPWTd均较对照组增高(P<0.05),疾病组孕妇舒张功能减低者较对照组增多(P<0.05),疾病组胎儿右心室Tei指数较对照组增高(P<0.05),与孕妇血压呈正相关(P<0.05),疾病组胎儿BDP、HC、AC、FL均较对照组减小(P<0.05)。结论通过对妊娠期高血压疾病孕妇母胎心功能及胎儿生长发育超声参数的研究,可对妊娠期高血压疾病母胎情况进行监测。     

Sonographic evaluation of fetal growth and body composition in women with different degrees of normal glucose metabolism

OBJECTIVE: To investigate the maternal demographic and metabolic factors contributing to the growth of fetal lean and fat body mass in women whose degree of glucose intolerance is less than that defining gestational diabetes in comparison with women with normal glucose metabolism. RESEARCH DESIGN AND METHODS: Longitudinal sonographic examinations of 66 singleton fetuses without anomalies of nonobese mothers with abnormal oral glucose challenge test (GCT) results and without gestational diabetes (group 1) were compared with those of 123 singleton fetuses without anomalies of nonobese mothers with normal GCT values (group 2). Lean body mass measurements included head circumference, femur length, mid-upper arm, and mid-thigh central areas. Fat body mass measurements included the anterior abdominal wall thickness, the subscapular thickness, and the mid-upper arm and mid-thigh subcutaneous areas. All the women performed a 24-h glucose profile on the day preceding the ultrasound scan. Multivariate logistic regression analysis established best-fit equations for fetal sonographic measurements of fat and lean body mass. Independent variables included groups 1 and 2, maternal age, parity, prepregnancy BMI, gestational age, weight gain during pregnancy, fetal sex, and the following averaged 24-h profile maternal capillary blood glucose values: preprandial, 1-h postprandial, and 2-h postprandial. RESULTS: No difference was found between the two groups with respect to fetal lean body mass parameters; the factors that contributed significantly and most frequently were gestational age and fetal sex (male). With respect to fetal fat body mass, all the measurements were significantly higher in group 1 than in group 2. In all instances, the significantly contributing factors were gestational age and maternal 1-h postprandial glucose values, whereas another frequent contributor was prepregnancy BMI. CONCLUSIONS: Our study suggests the possibility of using sonographically determined fetal fat and lean mass measurements as indicators of body composition. The assessment of these parameters, achievable in a noninvasive and reproducible fashion in pregnancies complicated by glucose intolerance, might enable the real-time detection of fetal overgrowth and disproportion, thus opening the possibility of exploring interventions to limit fetal fat accretion, birth weight, and potential resulting morbidity.     

Power spectrum analysis of heart rate and blood flow velocity variability measured in the umbilical and uterine arteries in early pregnancy: a comparative study.

OBJECTIVE: To compare power spectral derived variability parameters from the fetal side of the placental circulation with those from the maternal side of the placental circulation, during early pregnancy. METHODS: Doppler velocity waveforms were obtained from both the umbilical and the uterine arteries in a study group of 40 pregnant women between 10 and 14 (n = 25) and 15 and 20 (n = 15) weeks of gestation. The coefficient of variation of both the beat-to-beat heart rate variability and the blood flow velocity variability was determined. The ratio of the integrated low-frequency components (< 0.2 Hz) and the integrated high-frequency components (> 0.2 Hz) from normalized power spectrum analysis (LH-ratio) was established, to reflect sympathovagal balance. RESULTS: The coefficient of variation and LH-ratio of fetal heart rate variability constitute only a fraction of the same maternal heart rate variability parameters. Nevertheless a highly significant increase (P < 0.001) in LH-ratio was demonstrated with advancing gestational age. The coefficient of variation and LH-ratio of blood flow velocity variability were significantly lower in the fetal umbilical artery only in the 10-14-weeks' gestation group. Due to a decrease of the maternal uterine blood flow velocity variability parameters with advancing gestational age, statistically equal fetal and maternal values for coefficient of variation and LH-ratio were found in the 15-20 weeks' gestation group. CONCLUSIONS: The increase in LH-ratio of fetal heart rate variability indicates functional development of the fetal autonomic nervous system at 15-20 weeks' gestation. The umbilical blood flow velocity variability may be secondary to maternal uterine arterial flow variability rather than due to primary changes in fetal cardiovascular function.     

The fidgety fetus hypothesis: fetal activity is an additional variable in determining birth weight of offspring of women with diabetes

OBJECTIVE: To determine whether some offspring of women with diabetes are intrinsically more active than others in utero and whether those who are active are able to normalize their birth weight despite maternal hyperglycemia. RESEARCH DESIGN AND METHODS: We conducted a three-phase study to view the relationship between fetal movements and subsequent birth weight in women with diabetes. Phase I was designed to assess maternal perception of fetal movements in a population of 10 women with diabetes. To improve our fetal monitoring techniques, in phase II we analyzed fetal movements using the Card Guard home fetal monitoring device (CG 900P) in a population of 13 women with gestational diabetes mellitus (GDM). To apply our observations of fetal movements to a larger population, during phase III we conducted a retrospective analysis of fetal monitoring strips (HP 8041A) from 46 women with GDM to examine the relationship between fetal heart rate (FHR) accelerations and percentile birth weight, corrected for gestational age. RESULTS: Phase I confirmed that there is little variability in fetal movements (i.e., fetal kicks did not significantly deviate from one another on a day-to-day basis). In phase II, the fetal monitoring strips illustrated that the active fetuses (defined as > or = 4 FHR accelerations in a 20-min period) were always active, and the inactive fetuses were always inactive. The mean birth weight percentile, corrected for gestational age, in the active group was 37 vs. 63% in the inactive group (P = 0.05). In phase III, the fetal monitoring strips showed an inverse correlation between the mean number of FHR accelerations and the birth weight of the fetus, corrected for gestational age. The mean birth weight percentile in the active group was 37 vs. 62% in the inactive group (P = 0.0017). CONCLUSIONS: The fetus appears to play a role in determining its own destiny. Increased fetal activity may minimize the impact of hyperglycemia on subsequent birth weight. The inactive fetus appears to be at a higher risk for glucose-mediated macrosomia.     

Influence of different breathing patterns on heart rate variability indices and reproducibility during experimental endotoxaemia in human subjects

HRV (heart rate variability) analysis is a widely employed method to assess cardiac autonomic nervous system activity. Accurate HRV measurement is critical to its value as a diagnostic and prognostic tool. Different breathing patterns may affect HRV, but results obtained under static conditions are conflicting. HRV indices decrease considerably during systemic inflammation evoked by experimental endotoxaemia, enabling the determination of the effects of different breathing patterns on HRV in a dynamic setting. We investigated the impact of different breathing patterns on short-term HRV measurements during experimental endotoxaemia. Furthermore, we assessed whether paced breathing improved HRV reproducibility. Twelve healthy male volunteers received an intravenous bolus (2?ng/kg of body weight) of endotoxin [LPS (lipopolysaccharide), derived from Escherichia coli O:113] on two occasions with an interval of 2?weeks. Five-minute HRV recordings were performed just prior to LPS administration and hourly thereafter until 8?h post-LPS. Three breathing protocols were employed every hour: (i) spontaneous breathing, (ii) metronome-guided breathing at the subject's normal respiratory rate ('paced') and (iii) metronome-guided breathing at 150% of the subject's normal respiratory rate ('mild hyperventilation'). LPS administration resulted in a sharp decrease in all of the HRV indices measured, which was similar during both LPS administrations. Neither paced breathing nor mild hyperventilation influenced HRV indices compared with spontaneous breathing. Paced breathing did not improve reproducibility as it did not exert a significant effect on intra-subject coefficients of variation and intra-class correlation coefficients (calculated between both visits). In conclusion, over a wide range of HRV magnitudes during experimental endotoxaemia, neither paced breathing nor mild hyperventilation affected HRV indices. Moreover, paced breathing did not result in a significant improvement in reproducibility. Therefore employing a paced breathing protocol is not required to obtain valid HRV data during endotoxaemia.     

Suppression of heart rate variability after supramaximal exertion

Wingate test is short anaerobic exercise, performed with maximal power, whereas aerobic exercise at 85% maximal heart rate (HR(max)) may be performed for long period. Sustained HR elevations and changes in autonomic activity indices have been observed after latter kind of exercise. Several studies reported reduction in mean interval between consecutive R peaks in ECG (RRI) 1 h after Wingate test; however, underlying changes in autonomic activity remain elusive. In eight young males, RRI and heart rate variability (HRV) were measured daily over two 5-day trials. Subjects exercised on third day of each trial, measurements were taken 1 h after (i) two consecutive 30-s bouts of Wingate tests or (ii) after a 30-min exercise at 85% HR(max), with subjects in supine rest and breathing either spontaneously or at controlled rates of 6 and 15 breaths / min. RRI was significantly shorter after Wingate and submaximal exercise, reduction of high- and low-frequency components of HRV attained reliability only after Wingate tests. This pattern remained preserved for three modes of breathing: spontaneous, 6 and 15 breaths /min. After 24 and 48 h, no exercise effects were traceable. We hypothesize that (i) anaerobic exertion is followed by sustained inhibition of vagal activity, (ii) parasympathetic system plays dominant role in mediating suppression of high- and low-HRV frequency components during postexercise recovery, (iii) degree of alteration of autonomic activity caused by anaerobic and strenuous aerobic exercise may be similar and (iv) normalization of vagal activity precedes normalization of sympathetic cardiac nerves activity during final stage of postexercise recovery.     

Eighteen years of fair glycemic control preserves cardiac autonomic function in type 1 diabetes

OBJECTIVE: To study the association between 18 years of mean HbA(1c) and cardiac autonomic function in type 1 diabetic patients having used intensive insulin treatment. RESEARCH DESIGN AND METHODS: A total of 39 patients with type 1 diabetes were followed during 18 years, and HbA(1c) was measured yearly. At 18 years follow-up heart rate variability (HRV) measurements were used to assess cardiac autonomic function. Standard cardiac autonomic tests during normal breathing, deep breathing, the Valsalva maneuver, and the tilt test were performed. Maximal heart rate increase during exercise electrocardiogram and minimal heart rate during sleep were also used to describe cardiac autonomic function. RESULTS: We present the results for patients with mean HbA(1c) <8.4% (two lowest HbA(1c) tertiles) compared with those with HbA(1c) > or = 8.4% (highest HbA(1c) tertile). All of the cardiac autonomic tests were significantly different in the high- and the low-HbA(1c) groups, and the most favorable scores for all tests were seen in the low-HbA(1c) group. In the low-HbA(1c) group, the HRV was 40% during deep breathing, and in the high-HbA(1c) group, the HRV was 19.9% (P = 0.005). Minimal heart rate at night was significantly lower in the low-HbA(1c) groups than in the high-HbA(1c) group (P = 0.039). With maximal exercise, the increase in heart rate was significantly higher in the low-HbA(1c) group compared with the high-HbA(1c) group (P = 0.001). CONCLUSIONS: Mean HbA(1c) during 18 years was associated with cardiac autonomic function. Cardiac autonomic function was preserved with HbA(1c) <8.4%, whereas cardiac autonomic dysfunction was impaired in the group with HbA(1c) > or = 8.4%.     

Effects of haemodialysis on heart rate variability in chronic renal failure

The influence of haemodialysis (HD) on the heart rate variability (HRV) was investigated in nine non-diabetic patients on maintenance haemodialysis. The R-R intervals were measured in recordings during spontaneous quiet breathing and during controlled deep breathing before and after a single HD session. The HRV was expressed as the standard deviation of the mean R-R interval in 3 min ECG recordings. Heart rate variability is the irregularity in the heart rate mainly caused by autonomic control mechanisms. The long-term HRV during quiet breathing was statistically significantly (p less than 0.05) higher after the HD than before. The HRV in the intermediate frequency range of 0.075-0.125 Hz was also significantly increased by the HD. This suggests that some metabolic agents interfering with the heart rate regulation are removed by the haemodialysis, and as a result a better function of the autonomic cardiac control is achieved in uraemic patients.     

Linear and non-linear heart rate variability measures in chronic and acute phase of anorexia nervosa

Previous results on heart rate variability (HRV) analysis in anorexia nervosa (AN) include some apparently conflicting data. In order to find out the reason for different results and to improve understanding of autonomic control in AN we compare HRV in acute and chronic AN. Spectral powers, fractal scaling exponent and sample entropy were computed from 24 h RR series derived from Holter ECG recordings in 17 anorexic patients, nine chronic and eight healthy women. We found that all linear and non-linear HRV measures change in different direction in acute and chronic AN. Acute AN is characterized by decreased HR and increased HRV. In chronic AN, HR is increased, HRV reduced and the difference between awake and sleeping values is high. HRV measures are associated with body mass index only in chronic AN. As HRV measures are significantly different between acute and chronic AN, we propose that HRV analysis might provide additional data in clinical practice.     

Changes in the cardiac autonomic control system during rehabilitation in children after severe traumatic brain injury

BackgroundOne of the sequalae of severe traumatic brain injury (TBI) in children is impaired function of the cardiac autonomic control system (CACS) at rest. The CACS response to conventional autonomic tests is little known.ObjectiveTo examine the CACS response to conventional autonomic tests in children after severe TBI during the rehabilitation period and to compare with typically developing (TD) children.MethodsThis study combined a case-control and follow-up design. The severe TBI group (cases) consisted of 33 children aged 9–18 years, 14–142 days after severe TBI who were followed for 8 weeks during rehabilitation. The control group consisted of 19 TD children matched for age and sex. Heart rate (HR) and heart rate variability (HRV) were evaluated with the Polar RS800CX device at rest (sitting), during a handgrip test and during a paced breathing test.ResultsAt the first assessment, we found lower HRV values at rest and a lower HRV response during the paced breathing and handgrip tests in the TBI group than the TD group (p<0.01). After 8 weeks, HRV values did not change at rest in the TBI group, but the response to the autonomic tests improved significantly, with increased HRV values in response to the paced breathing test (p<0.01) and the handgrip test (p = 0.01).ConclusionsAfter severe TBI, children exhibited an impaired CACS response to autonomic tests, with parasympathetic suppression and sympathetic arousal. After 8 weeks of rehabilitation, CACS function recovered partially and the response to the autonomic tests improved with no change in CACS function at rest.     

N-terminal pro-C-type natriuretic peptide, but not C-type natriuretic peptide, is greatly elevated in the fetal circulation

We have identified recently a new peptide, NT-proCNP(1-50) (N-terminal pro-C-type natriuretic peptide), in the circulation of humans and sheep. A previous report of an elevated fetal-maternal gradient in immunoreactive CNP raised the possibility that processing and metabolism of proCNP may differ in maternal and fetal tissues. We therefore collected matching peripheral maternal and umbilical cord plasma samples at delivery from women with normotensive and pre-eclamptic pregnancies to investigate the presence and concentrations of CNP and NT-proCNP using HPLC and RIA. Plasma concentrations of NT-proCNP in normotensive umbilical cord plasma were 10-fold higher than maternal venous levels (246+/-17 compared with 24.3+/-1.8 pmol/l; P <0.001) and much higher than corresponding levels of CNP (3.6+/-0.4 compared with 1.8+/-0.3 pmol/l in the fetal and maternal plasma respectively; P <0.001). Although there was no significant difference between normotensive and pre-eclamptic plasma CNP concentrations in either maternal or umbilical cord blood, NT-proCNP showed a significant statistical interaction ( F =5.8, P =0.025) between the source (maternal or fetal) and gestational group (normotensive or pre-eclamptic). Maternal NT-proCNP levels were raised in the pre-eclampsia group, whereas the converse was observed in umbilical cord blood. In conclusion, the greatly elevated ratio of NT-proCNP/CNP in fetal compared with maternal plasma suggests that synthesis, as well as clearance, of CNP (but not NT-proCNP clearance) are markedly increased in fetal tissues.     

On- and off-responses of heart rate to exercise - relations to heart rate variability

During physical exercise, heart rate (HR) increases by parasympathetic withdrawal and increase of sympathetic activity to the heart. HR variability (HRV) in time and frequency domains provides information about autonomic control of the cardiovascular system. Non-linear analysis using the Poincaré plot method is able to reveal supplementary information about cardiac autonomic control. The aim of this study was to determine the association between HRV parameters, the initial increase of HR at the onset of exercise (on-response) and HR decrease in the recovery phase after acute exercise (off-response). HR was continuously monitored in 17 healthy male subjects (mean age: 20.3 +/- 0.2 (SEM) years) at rest (25 min supine; 5 min standing), during exercise (8 min of step test at 70% of maximal power output) and in the recovery phase (30 min supine). HRV analysis in time and frequency domains and evaluation of the Poincaré plot measures (length, widths) were performed on selected segments of HR time series. HR on- and off-responses were quantified using an exponential curve fitting technique. The time constants T(on) and T(off), representing the rate of on- and off-responses to exercise, were computed. Postexercise HRV indices and time constant of on-response - T(on) - to exercise were negatively correlated. From preexercise HRV indices, only Poincaré plot parameters were correlated with T(on). No correlation between HRV indices and parameters of off-response was found. In conclusion, preexercise HRV parameters are not closely correlated with the rate of cardioacceleration at the onset of exercise and cannot predict the rate of HR recovery. On the other hand, postexercise HRV parameters are related to the rate of initial adjustment of HR to exercise referring to the importance of rapid HR on-response for a faster recovery after exercise.     

组织多普勒成像和时间-空间相关成像评价孕晚期子痫前期胎儿心脏功能的应用价值

目的 应用组织多普勒成像（TDI）和时间-空间相关成像（STIC）评价孕晚期子痫前期孕妇的胎儿心脏功能,探讨其临床应用价值。方法 选取于我院产检并确诊的孕晚期子痫前期孕妇121例,其中轻度子痫前期孕妇61例（MPE组）,重度子痫前期孕妇60例（SPE组）,另选同期孕晚期正常妊娠孕妇115例为正常对照组,按照孕28～31+6周、32～35+6周、36～40周3个时间段分别应用TDI和STIC连续评估各组胎儿心脏功能,测量二、三尖瓣环舒张早期运动速度（Ea）、舒张晚期运动速度（Aa）、收缩期运动速度（Sa）,以及等容收缩时间、等容舒张时间及射血时间,计算左、右室Tei指数和短轴缩短分数（SF）,以及二、三尖瓣环Ea/Aa,比较各组上述参数的差异。结果 SPE组、MPE组孕28～31+6周、32～35+6周、36～40周二、三尖瓣环Sa、Ea/Aa及左、右室SF均小于正常对照组,左、右室Tei指数均大于正常对照组,差异均有统计学意义（均P<0.05）。SPE组孕36～40周左、右室SF均小于MPE组,左室Tei指数大于MPE组,差异均有统计学意义（均P<0.05）;SPE组孕28...