摘要:

BackgroundNewer techniques to evaluate baroreflex sensitivity (BRS) are based on the analysis of blood pressure (BP) and heart rate (HR) time series in the time or frequency domain. These novel approaches are steadily gaining popularity, since they do not require injection of vasoactive substances, nor do they rely on a complex experimental set-up.AimThis review outlines and compares some basic features of the latest methods to assess spontaneous baroreflex function.ResultsModern techniques for the estimation of spontaneous BRS are based on a variety of signal processing schemes and derive information on the baroreflex function from different perspectives. Thus factors such as respiration and other non-stationary agents may have different influences on the estimates provided by each of these approaches. Notwithstanding such individual specificity, however, it has been observed that in several physiological and pathophysiological conditions these techniques often provide comparable information on BRS changes over time, particularly when the estimates are averaged over time windows of a few minutes.ConclusionsDue to the general agreement in the pattern of BRS among most modern methods, it seems reasonable to employ the most validated of these techniques, for which data obtained in several studies are already available.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Although sympathetic nervous activity (SNA) displays oscillations synchronous with the heart beat and respiration, and between 0.1–0.4 Hz, it is apparent that each of these frequencies does not have the same effect on the vasculature. Frequencies above1Hz do not produce oscillations in the vasculature but instead contribute to the mean level of vasoconstriction. Slower oscillations in SNA result in a cycle of vasoconstriction and vasodilation within the vasculature, the amplitude of which, generally decreases with increasing frequency. Some studies indicate that, within the same species, differences exist in the frequency responses between vascular beds, such as the skin and gut. This differential responsiveness is also found between the medullary and cortical vasculature regions of the rabbit kidney. Low-pass filter properties have been described in the iliac circulation of rats, and evidence has been provided that noradrenaline reuptake mechanisms are not the frequency limiting step of the vasculature response. Recent studies on isolated rat vascular smooth muscle cells suggest that sympathetic modulation of vascular tone is limited by the α-adrenoceptor signal transduction into the cells and not by an intrinsic inability of the cells to contract and relax at higher rates.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectivesTo determine the prevalence and treatment status of hypertension in South Africa.DesignNational cross-sectional survey.Setting13 802 randomly selected South Africans, 15 years and older, were visited in their homes in 1998.MethodsTrained fieldworkers completed questionnaires on lifestyle and chronic diseases, measured blood pressure with an Omron manometer and recorded chronic drug utilization. Drugs were classified using the Anatomical Therapeutic Chemical index.ResultsThe mean systolic blood pressure for men and women was 123 mmHg (SE 0.37) and 119 mmHg (SE 0.36), while the mean diastolic level was 76 mmHg (SE 0.25) and 75 mmHg (SE 0.20), respectively. When using a cut-off point of 140/90 mmHg the hypertension prevalence rate (age-adjusted to the South African Population, Census 1996) was 21% for both genders. Using the current cut-off point (160/95 mmHg) for South Africa, the prevalence rate was 11% for men and 14% for women. For men with hypertension, the level of awareness, taking antihypertensive medication and having controlled blood pressure (<160/95 mmHg) were 41, 39 and 26% respectively, while for women these rates were 67, 55 and 38% respectively.ConclusionsThis survey revealed high levels of hypertension in the South African community with inadequate treatment status.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveTo estimate, with respect to age and gender, the prevalence of high blood pressure (BP) in treated and non-treated subjects and its association with other cardiovascular risk factors.DesignA cross-sectional study.SettingHealthcare centres in the centre of France.ParticipantsAll subjects (n= 61 108) who had a free health check-up, between February 1995 and September 1996.Main outcome measuresHigh BP (systolic blood pressure (SBP)>140 mmHg, diastolic blood pressure (DBP)>90 mmHg or antihypertensive therapy); diabetes (fasting glucose plasma concentration>1.26 g/l or antidiabetic therapy); hypercholesterolaemia (total cholesterol>2 g/l or lipid-lowering therapy); hypertriglyceridaemia (fasting triglycerides plasma concentration>2 g/l or triglyceridaemia-lowering therapy); overweight (body mass index⩾25 kg/m2); abdominal fat distribution (waist to hip ratio>0.9 in males and>0.8 in females).ResultsPrevalence of high BP was 37.7% in males and 22.2% in females. BP was normalized in 29.7% of treated males and 44.1% of treated females. High BP was associated with at least another cardiovascular risk factor in 83.8% of the males and 76.7% of the females with high BP. Hypercholesterolaemia was the most frequently associated risk factor. Except smoking, the prevalence of each cardiovascular risk factor was shown to increase with the severity of hypertension. Two or more other cardiovascular risk factors were present in 22.9% of the males and 9.8% of the females with high BP.ConclusionsRate of high BP, even in treated subjects, is high. More than three out of four subjects with high BP have at least one other cardiovascular risk factor.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectivesTo evaluate the long-term effects of regular moderate or vigorous intensity exercise on blood pressure and blood lipids in previously sedentary older women.DesignSubjects were randomly assigned to either a supervised centre-based (CB) or a minimally supervised home-based (HB) exercise program, initially for 6 months. Within each program, subjects were further randomized to exercise either at moderate (40–55% heart rate reserve, HRres) or vigorous intensity (65–80% HRres). After 6 months, all groups continued a HB moderate or vigorous exercise program for another 12 months.MethodsHealthy, sedentary women (aged 40–65 years) (n= 126) were recruited from the community. Subjects exercised three times per week for 30 min. They were evaluated at baseline, 6, 12 and 18 months.ResultsThere was a significant fall of 2.81 mmHg in systolic blood pressure (P= 0.049) and 2.70 mmHg in diastolic blood pressure (P= 0.004) after correction for age and baseline values with moderate exercise, but not with vigorous-intensity exercise. When this analysis was repeated with the change in body mass included, the results were unchanged. After correction for potential confounding factors, there was a significant fall in total cholesterol and low density lipoprotein cholesterol with vigorous but not moderate exercise at 6 months (P<0.05) but not at 18 months.ConclusionsIn this largely normotensive population of older women, a moderate, but not vigorous exercise program, achieved sustained falls in resting systolic and diastolic blood pressure over 18 months. The study demonstrates that, in older women, moderate intensity exercise is well accepted, sustainable long-term and has the health benefit of reduced blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveWhile the exact regulatory interactions between blood pressure (BP) and obesity are not completely understood, weight loss provides an alternative to pharmacological treatment of hypertension. The intent of this repeated measures study of mild–moderate hypertensive, moderately obese subjects (34 females/18 males) was to determine if the reduction in BP following weight loss could be further affected by modifying the fatty acid (FA) composition of the hypocaloric diet.MethodsBP, insulin sensitivity (Si), and lipid parameters were assessed before and after a 10-week calorie-restricted period. Subjects were randomized to one of three dietary groups differing in FA composition. Reduced body weight was maintained for a further 4 weeks and body composition assessment, BP and heart rate measurements were repeated.ResultsWeight loss (10%) in obese hypertensive subjects resulted in substantial improvements in BP, Si and lipid profile. There was no additional effect on the reduction in BP by the type of FA consumed in the diet. Following weight loss, there was a trend for omega-3 FAs to have a protective effect on fat-free mass loss (compared to omega-6 FA Group and saturated FA Group) and a trend to further enhance Si. There were significant improvements in circulating lipid profiles independent of the dietary FA intervention following the weight loss. The improvements in BP and body composition were maintained during the weight-loss maintenance period. The type of fat consumed had minor differential effects on some of the measured metabolic outcomes.ConclusionThese results provide strong support for modest weight loss as a treatment for hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

Background and aimsThe Hypertension Optimal Treatment (HOT) study showed that when antihypertensive treatment reduces diastolic blood pressure well below 90 mmHg, there can be a further reduction of cardiovascular events, particularly myocardial infarction, with no evidence of a J-shaped curve at lower pressures. Office measurement, however, gives no information about blood pressure outside the office. This paper describes a HOT substudy in which patients underwent both office measurement and 24 h ambulatory blood pressure monitoring.MethodsThe mean age of the substudy population was 62±7 years. Substudy patients were treated for a median period of 2 years. All received the dihydropyridine calcium antagonist felodipine, while some also received an ACE-inhibitor, a beta-blocker or a diuretic. Average 24 h, day and night ambulatory blood pressure values were computed at baseline (n= 277) and during treatment (n= 347): 112 patients had been randomized to a target office diastolic blood pressure ⩽ 90 mmHg, 117 to⩽85 mmHg and 118 to⩽80 mmHg. Additional analyses included computation of: (1) trough-to-peak ratio and (2) the smoothness index (the ratio between the average of the 24 hourly blood pressure reductions after treatment and its standard deviation).ResultsTaking the subgroup as a whole, baseline 24 h average blood pressures (146±18/90±10 mmHg) were significantly and markedly lower than office blood pressures (170±14/105±3 mmHg,P< 0.01). Office, 24 h, day and night blood pressures were all significantly reduced by treatment, but there was a smaller fall in ambulatory, than in office pressures. The between group differences in office blood pressure were smaller than those observed in the overall HOT sample. Between-group differences in 24 h blood pressure were even smaller. Trough-to-peak ratios and smoothness indices were lowest in the highest blood pressure target group and highest in the lowest blood pressure target group. Office and ambulatory blood pressures were similar in the groups randomized to placebo (n= 170) or acetylsalicylic acid (n= 177).ConclusionIn conclusion, in the HOT study, treatment reduced not only office but also ambulatory blood pressure throughout the 24 h. The reduction was less marked for ambulatory than for office blood pressure.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveTo show that different methods of data analysis affect the grading that blood pressure measuring devices achieve according to the British Hypertension Society (BHS)-protocol.MethodsBased on the somewhat unclear description of the exact method of data analysis in the BHS-protocol four different methods can be discerned. The effect on the grading-results is calculated for these four different options.Results and ConclusionsIt is shown that using these four different options the achieved grade can range for diastolic blood pressure from C (option 1) to almost A (option 4) and for systolic blood pressure from D (option 1) to B (option 4). Different researchers may well have used different methods. Option 1 is the method that should be used. Also it is stated that the systematic error and the standard deviation of differences (SDD) are measures that give more insight to describe a device's performance. Calculating the grades after correction for the systematic error shows its influence and that of the SDD on the reported accuracy of a blood pressure measuring device.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

We investigated the effect of antisense oligodeoxynucleotides (AS ODN) against tyrosine hydroxylase (TH) on hypertension and sympathetic nervous system activity in spontaneously hypertensive rats (SHR). Systolic blood pressure (SBP) in SHR treated with TH AS ODN (50, 200 μg/rat, i.v.) was significantly lower than that of control SHR. Epinephrine and norepinephrine levels, TH activity, and TH protein levels in the adrenal medulla of SHR were reduced concomitant with TH AS ODN treatment-induced changes in SBP. In contrast, TH AS ODN (200 μg/rat) had no effect on SBP in Wistar–Kyoto rats (WKY), despite significantly decreased catecholamine levels, TH activity, and TH protein levels. These findings suggest that peripheral systemic injection of TH AS ODN may be effective as hypotensive therapy in SHR.

ISSN:0263-6352    

出版商:OVID    

年代:2001

数据来源: OVID