Circadian time-qualified tolerance intervals for ambulatory blood pressure monitoring in the diagnosis of hypertension.

Hermida RC, Fernandez JR, Ayala DE, Mojon A, Alonso I, Calvo C.

Bioengineering Laboratory, University of Vigo, Campus Universitario, Vigo, Spain. rhermida tsc.uvigo.es

The large-amplitude circadian pattern in blood pressure of healthy subjects of both genders suggests that the constant threshold currently used to diagnose hypertension should be replaced by a time-specified reference limit reflecting the mostly predictable blood pressure variability during the 24 h. Accordingly, we derived circadian time-specified reference standards for blood pressure as a function of gender. We studied 743 normotensive Caucasian volunteers (400 men and 343 women), 45.7 +/- 16.5 (mean +/- SD) years of age. Blood pressure was measured by ambulatory monitoring at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual in order to avoid differences among subjects in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each gender separately. The method, derived on the basis of bootstrap techniques, does not need to assume normality or symmetry in the data and, therefore, it is highly appropriate to describe the circadian pattern of blood pressure variability. Results reflect expected changes in the tolerance limits as a function of gender and circadian sampling time, as well as upper blood pressure limits below the thresholds currently used for diagnosing hypertension, especially for women. The use of these time-dependent tolerance limits for the computation of a hyperbaric index as a measure of blood pressure excess has already been shown to provide a reproducible and high-sensitivity test for the diagnosis of hypertension, which can also be used to evaluate treatment efficacy.

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Impact of pregnancy-induced hypertension on birthweight by gestational age.

Xiong X, Fraser WD.

Department of Obstetrics and Gynecology, University of Montreal, Quebec, Canada. xxiong tulane.edu

Few studies to date have examined the effect of severe pre-eclampsia, pre-eclampsia, and gestational hypertension on birthweight according to gestational age. We conducted a population-based retrospective cohort study of 16,936 pregnant women in Suzhou, China. Analysis of variance and multivariable linear regression were performed to compare the mean birthweights of babies born to mothers with gestational hypertension, pre-eclampsia, and severe pre-eclampsia with birthweights of infants born to mothers with normal blood pressure at each week of gestation. The differences in mean birthweight between women with severe pre-eclampsia and women with normal blood pressure ranged between -467.7 g and 189.1 g. The birthweights were statistically significantly lower in women with severe pre-eclampsia than in women with normal blood pressure for gestational age categories < or = 35 and 36 weeks. However, after adjustment for confounding variables, the birthweights were not statistically significantly different in women with severe pre-eclampsia when compared with women with normal blood pressure even at < or = 35 and 36 weeks. The differences in mean birthweight between women with pre-eclampsia and women with normal blood pressure ranged between -132.2 g and 174.6 g. These differences were not statistically significant, before or after adjusting for confounding variables. There were no differences in mean birthweight between women with gestational hypertension and women with normal blood pressure. Further analysis suggested that pre-eclampsia and gestational hypertension were associated with increased rates of both small-for-gestational-age and large-for-gestational-age infants. The majority of the babies born to mothers with different types of pregnancy-induced hypertension were appropriate-for-gestational-age or even large-for-gestational-age. In this Chinese population, most babies born to mothers with severe pre-eclampsia or pre-eclampsia and gestational hypertension had similar fetal growth to those born to normotensive mothers.

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[The study on relationship of body mass index and blood pressure in children and adolescents of Beijing]

[Article in Chinese]

Wang WJ, Wang KA, Chen CM, Cao RX, Bai YM, Ma LM, Ren ZY, Niu ZH, Gao Q.

National Center for Chronic and Noncommunicable Disease Prevention and Control, Chinese Center for Disease Prevention and Control, Beijing 100050, China.

OBJECTIVE: To identify the relationship of body mass index (BMI) and blood pressure in 7 - 15 years children and adolescents of Beijing so as to provide scientific basis for early prevention of hypertension and to provide evidence for verification on the category criterion of overweight and obesity in children and adolescents of China, recommended by the Working Group on Obesity in China (WGOC) to sensitively distinguish the blood pressure in normal weight, overweight and obesity populations. METHODS: A cross-sectional survey on epidemiological characteristics of obesity with stratified cluster sampling method carried out in Beijing in April and May, 2000. 5155 students aged 6 - 15 years were selecte das research subjects. The category criterion of overweight and obesity in children and adolescents of China was recommended by WGOC, the diagnostic criterion of hypertension in children was recommended by CDC in the USA. Statistics analysis system (SAS 8.1) including partial person correlation analysis, t-test, chi(2) test and logistic multi-factors regression analysis was used to analyses the data from 4982 subjects aged 7 - 15 years. RESULTS: (1) after the age and gender were adjusted, the BMI positive correlation with systolic blood pressure (SBP) and diastolic blood pressure (DBP) was found independent in 7 - 15 years children and adolescents (P < 0.0001) and the partial relation coefficients(r) between BMI and SBP and DBP were 0.323 87 and 0.245 88 respectively. (2) the means of SBP and DBP in obesity group were significantly higher then overweight, while overweight was significantly higher then normal weight group (P < 0.0001). (3) the prevalence rates of hyper-SBP, hyper-DBP and hypertension were significantly different (P < 0.0001). When compared with the normal weight group, the relation risk (RR) for hypertension in overweight group and obesity group were 2.96 and 4.85 respectively. The prevalence rates of hypertension in overweight and obesity group were 19.70% and 24.22% respectively. (4) the results of logistic multi-factors regression analysis showed that both age and weight were effecting on hyper-SBP, hyper-DBP and hypertension (P < 0.0001). After age was adjusted, the RR for hypertension was 2.62, and their confidence interval (CI) was 2.36 - 2.91 in obesity or overweight, between overweight and normal weight. CONCLUSION: (1) the BMI positive correlation with SBP and DBP was found independent in 7 - 15 years children and adolescents of Beijing, and the risk for hypertension maybe increased when these people with overweight and obesity, it is very important for hypertension prevention and control that overweight and obesity prevention and control in children and adolescents. (2) the sensitivity of the category criterion of overweight and obesity in children and adolescents of China, recommended by WGOC have been verified on distinguish the blood pressure in normal weight, overweight and obesity populations.

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[Changes of endogenous hydrogen sulfide (H2S) in hypertensive rats]

[Article in Chinese]

Yan H, Du JB, Tang CS.

Department of Pediatrics, First Hospital, Peking University, Beijing 100034, China.

OBJECTIVE: Hydrogen sulfide, a well known toxic gas, has been found to play important roles in many organs and tissues, especially in cardiovascular system recently. The aim of this study was to explore the producing rate of hydrogen sulfide (H(2)S) in aorta and the level of H(2)S in plasma of spontaneous hypertensive rats (SHR), and to study the role of H(2)S on the development of hypertension. METHODS: Twenty-four male SHR rats at the age of 4 weeks were randomly divided into SHR control group, SHR + NaHS (H(2)S donor) group and SHR + DL-propargylglycine (PPG) group, respectively. Another twenty-four male WKY rats were also divided into WKY control group, WKY + NaHS group and WKY + PPG group. SHR control and WKY control rats were injected with water. Rats of SHR + NaHS group and WKY + NaHS group were injected with NaHS, and rats of SHR + PPG group and WKY + PPG group were injected with PPG every day. Five weeks later, the blood pressure and the left-to-whole heart weight ratio were determined. The producing rate of H(2)S in aorta and the H(2)S level in plasma were also detected. RESULTS: The producing rate of H(2)S in aorta and the plasma level of H(2)S in SHR groups were all less than those of the corresponding WKY groups, however, the differences between SHR + PPG group and WKY + PPG group were not significant (P > 0.05). The producing rate of H(2)S and the plasma level of H(2)S in SHR + PPG group were similar to those of SHR control group. The producing rate of H(2)S and the plasma level of H(2)S in SHR + NaHS group were higher than those of SHR control. Both the producing rate and the plasma level of H(2)S in WKY + PPG group were less than those of WKY control. The producing rate of H(2)S in aorta of WKY + NaHS group was higher than that of WKY controls, while the plasma level of H(2)S in WKY + NaHS group was not different from that of WKY controls significantly. The blood pressure of SHR groups increased compared with that of WKY groups (P < 0.05). The blood pressure of SHR + PPG group was similar to that of SHR controls, while the blood pressure of SHR + NaHS reduced significantly compared with that of SHR controls. The blood pressure of WKY + PPG group was higher than that of WKY controls while the blood pressure of WKY + NaHS was similar to that of WKY controsl. CONCLUSIONS: H(2)S plays an important role in maintaining normal pressure and the reduced production of endogenous H(2)S is an essential factor in the development of spontaneous hypertension. Exogenous H(2)S provides a new way for interfering with the progression of hypertension.

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Effects of long-term captopril and L-arginine treatment on ventilation and blood pressure in obese male SHHF rats.

Schlenker EH, Kost CK Jr, Likness MM.

Division. of Basic Biomedical Sciences, University of South Dakota School of Medicine, Vermillion, South Dakota 57069, USA. eschlenk usd.edu

We investigated the effects of captopril (Cap) and L-arginine (Arg) on hypertension and cardiopulmonary function. Our hypothesis was that Cap therapy or Arg will improve cardiopulmonary risk factors for hypertension and hypoventilation in the obese spontaneously hypertensive heart failure rat, which is characterized by hypertension, obesity, and disorders of lipid and carbohydrate metabolism. For the first study, one group of rats received Cap in drinking water, and a second group received deionized water (DI). For the second study, rats were further subdivided. Some Cap-treated rats continued on this treatment, and the other half were now given DI to determine whether there would be residual effects of Cap treatment. A subgroup of rats who had received DI was then given Arg, whereas the rest remained on DI. In the first study, Cap-treated rats exhibited decreases in systolic and diastolic blood pressures, frequency of breathing, and minute ventilation, but ventilatory control was maintained. In contrast, blood pressures and relative ventilation to metabolism were higher in the DI-treated group. Removal of Cap increased blood pressure and decreased tidal volume while these rats maintained frequency. Although Arg-treated rats did not exhibit a decrease of blood pressure, ventilation was maintained in this group by preserving tidal volume. Thus Cap and Arg affected ventilation through different mechanisms independent of blood pressure.

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The Leu554Phe polymorphism in the E-selectin gene is associated with blood pressure in overweight people.

Marteau JB, Sass C, Pfister M, Lambert D, Noyer-Weidner M, Visvikis S.

Unite INSERM U525 Equipe 4 Centre de Medecine Preventive, Nancy, France.

BACKGROUND: Associations between circulating concentrations of E-selectin, blood pressure and obesity, and between the Leu554Phe (L/F554) polymorphism and blood pressure have been documented. OBJECTIVES: To investigate how the E-selectin L/F554 polymorphism is involved in longitudinal blood pressure changes, and how this polymorphism interacts with body mass index (BMI) on blood pressure. DESIGN AND PARTICIPANTS: For this study, 478 men and 546 women were selected from the Stanislas cohort, a French longitudinal study of volunteers for a free health check-up. These individuals underwent two examinations (t(0) and t(+5)) and were not taking medication that can affect blood pressure. RESULTS: At t(0), no relationship was observed between L/F554 polymorphism and blood pressure. However at t(+5), systolic blood pressure (SBP) was greater in individuals carrying the F allele, and the L/F554 polymorphism was associated with SBP in interaction with BMI (P < 0.001 in men and P < 0.05 for women). There was a steeper increase in SBP with BMI greater than 25 kg/m2 in carriers of the F allele than in LL homozygotes. Similar results were observed for diastolic blood pressure in men (P = 0.0103). CONCLUSION: These results suggest a BMI-specific effect of L/F554 polymorphism of the E-selectin gene on blood pressure, and strengthen the hypothesis that E-selectin is implicated in hypertension.

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Significant target organs for hypertension and cardiac hypertrophy by angiotensin-converting enzyme inhibitors.

Takai S, Jin D, Sakaguchi M, Miyazaki M.

Department of Pharmacology, Osaka Medical College, Takatsuki 569-8686, Japan. Pha010 art.osaka-med.ac.jp

To clarify the mechanisms by which angiotensin-converting enzyme (ACE) inhibitors lower blood pressure or inhibit cardiac hypertrophy, we analyzed the correlations among tissue ACE activities, blood pressure and cardiac hypertrophy. In spontaneously hypertensive rats (SHR), blood pressure, heart weight and ACE activities in plasma and various tissues were measured 3, 24 and 48 h after repeated daily treatment for 2 weeks with the ACE inhibitors trandolapril, perindopril, temocapril and enalapril. For all four ACE inhibitors, blood pressure and ACE activities in the plasma, aorta and kidney were significantly reduced 3 h after the last treatment. Although hypotensive effects were maintained at 24 h, ACE activities in plasma were not suppressed by temocapril and enalapril. Even at 3 h, enalapril could not suppress ACE activity in the brain, and temocapril and enalapril could not inhibit ACE activities in the heart. Significant correlations between ACE activity in the aorta and blood pressure were observed for all four ACE inhibitors, while the ACE activities in the heart and brain were not correlated with changes in blood pressure. Significant decreases in the ratio of heart weight to body weight were observed in SHR treated with trandolapril and perindopril, whereas they were not observed with temocapril and enalapril. The ratio of heart weight to body weight was significantly correlated with ACE activity in the heart. ACE activities in vascular tissues and the heart may be important targets in terms of the ability of ACE inhibitors to lower blood pressure or inhibit cardiac hypertrophy, respectively.

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High-sodium diets in Japanese evacuation centers increase blood pressures of evacuees.

Takechi S, Yoneda R, Mizuno R, Machida M, Fujimoto T, Kakinoki S, Kuroshima S, Nomura A.

Department of Cardiovascular Medicine, Date Red Cross Hospital, Date, Hokkaido, Japan.

AIMS: High blood pressure after a natural disaster is tentatively considered to be due to elevation of sympathetic nerve activity. A volcano in Japan erupted on March 31, 2000, and people living in the vicinity of the volcano were evacuated to safe shelters. We found that many evacuees developed high blood pressure while staying at evacuation centers. The aim of this study was to investigate why their blood pressures stayed elevated. METHODS AND SUBJECTS: Sixty-five evacuees, who were staying evacuation centers for 4 months, were examined for blood pressure, urinary sodium excretion, urinary potassium excretion, and plasma and urinary catecholamines. RESULTS: Associations were found between systolic blood pressure and sodium excretion (r = 0.311, p < 0.05) and between systolic blood pressure and the ratio of urinary sodium to urinary potassium (r = 0.320, p < 0.05). However, no association was found between blood pressure and plasma and urinary catecholamines (NE, DHPG and MHPG). CONCLUSION: High sodium consumption was thought to be an important factor in the elevation of blood pressure of the evacuees after acute phase reactions.

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