摘要:

Objective:To determine the clinical relevance of the newly described circulating pressor factor with parathyroid hypertensive factor (PHF)-like activity.Design:Plasma samples were collected from 94 normotensive and 93 essential hypertensive subjects, the latter either previously defined by dietary salt sensitivity (n = 43), or prospectively studied on both low- (<50 mmol/day) and high-salt (>200 mmol/day) diets (n = 16).Methods:Blood pressure, demographic factors, plasma renin activity (PRA), urinary electrolyte excretion and bioassayable PHF-like activity were determined in the fasted state on basal and altered dietary salt intakes.Results:Among the normotensive subjects significantly higher PHF-like activity and reciprocally lower PRA values were observed in Black versus Caucasian subjects, particularly among females. In the hypertensive subjects PHF-like activity levels were significantly elevated in the low- (17.1 ± 1.5 mmHg, n = 34) and normal- (6.7 ± 1.8 mmHg, n = 36) but not in the high-renin subgroups compared with values in the normotensive subjects (1.6 ± 1.1 mmHg). Similarly, PHF-like activity values were significantly higher in salt-sensitive than in salt-insensitive hypertensives. Prospectively, PHF-like activity rose significantly with salt loading (4.9±1.2 to 20.4±6.2mmHg) and was positively related (r = 0.648,P< 0.001) to the pressor response to salt.Conclusions:Elevated levels of PHF-like activity are characteristic of the low-renin or salt-sensitive state, or both, and may contribute to the hypertensive process. Elevated PHF-like activity levels found in normotensive subjects may presage the development of low-renin, salt-sensitive hypertension.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To investigate the relationship between left ventricular performance and sympathetic nervous activity.Design:We studied the α- and β-adrenergic responsiveness of the subjects and assessed their left ventricular performance.Methods:Fifty-four adult established hypertensive patients, all with apparent left ventricular hypertrophy, and 36 age-matched normotensive controls were studied. Thirty-four of the hypertensive patients were within the ±2SD confidence area of fractional shortening/end-systolic stress relation of the normotensive controls and are denoted subgroup A; 19 patients were below the lower limit and are denoted subgroup B. Isoproterenol and neosynephrine injection tests were used to assess β- and α-adrenergic responsiveness, respectively. Intravenous infusion tests using regitine and isoproterenol were performed in 16 patients to assess the effects of sympatho-adrenergic responsiveness on changes in left ventricular performance.Results:Afterload and left ventricular mass were similar in the two subgroups. Left ventricular performance and β-adrenergic responsiveness in subgroup A were comparable with the corresponding levels in the normotensives, whereas in subgroup B both were markedly decreased. The regitine infusion test induced a fall of 25% in peripheral resistance from baseline, but no significant improvement in left ventricular performance. In contrast, isoproterenol infusion test resulted in striking improvements: left ventricular performance increased by 60%, afterload decreased by 48% and peripheral resistance fell by 50% from baseline.Conclusion:The diminished ventricular performance and high resistance observed in adult established hypertension may be due to synergic effects of significantly reduced β-adrenergic responsiveness coupled with enhanced α-adrenergic responsiveness.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Design and methods:Local elastic properties of the descending aorta at different levels were evaluated by means of intravascular ultrasound images and pressure measurements. For this purpose, 30 normotensive patients and 30 age-matched medically treated patients with essential hypertension, all undergoing diagnostic cardiac catheterization, were studied.Results:Hypertension was well controlled in the essential hypertensives (137.1 ± 6.79/74.5±2.65 mmHg). Systolic but not diastolic blood pressure in the hypertensive patients was significantly different from that of the normotensives (118.8±4.38/69.7±1.65 mmHg). The continuous loss of volume compliance with increasing distance from the heart was significantly higher in the hypertensives than in the normotensive patients [normotensives (1.45 ± 0.19) x 10-10m5/Nat the thoracic aorta, (0.08 ± 0.05) x10-10m5/N at the external iliac artery; hypertensives (0.81±0.09)x10-10and (0.05±0.01)x10-10m5/N at the corresponding sites]. Similarly, the hypertensives had an elevated elastic modulus proximal to the aortic bifurcation compared with the normotensives (244.47±44.06 versus 108.10±17.76m/s, respectively). The decrease in buffering function of the vessel at this site is presumably caused by a turbulent flow pattern. Compared with the normotensives, the treated hypertensives had a significantly higher elastic modulus at each site where this was measured, whereas volume compliance and sectional compliance were lower.Conclusion:The differences in elastic modulus and compliance between hypertensive and normotensive patients seem disproportionate to the difference in systolic blood pressure (within the normal range in both the treated hypertensives and the normotensives). Therefore, normalization of high blood pressure by long-term antihypertensive treatment may not fully reverse changes, caused by arterial hypertension, in the viscoelastic properties of the arterial wall.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To study left ventricular function and morphology in non-hypertensive obese females and to relate the findings to body mass index (BMI) and to an index of body fat distribution (waist: hip ratio).Design:Cross-sectional study.Setting:Obesity unit in city hospital.Subjects:Healthy obese females (n = 22) with BMI >25 and <40 kg/m2and a non-obese, age-matched control group (n = 20) with BMI <25 kg/m2.Main outcome measures:Blood pressure and non-invasive indices of left ventricular morphology and diastolic and systolic function.Results:The obese group had significantly higher blood pressure, larger left ventricular end-diastolic diameter, greater left ventricular mass; larger left atrial size, signs of decreased left ventricular distensibility and prolonged left ventricular relaxation time index, and signs of supernormal systolic left ventricular function (as judged from the relationship between fractional shortening and end-systolic wall stress) than the non-obese controls. The results also indicated that left ventricular wall thickness and mass were well adapted to the increase in afterload, as judged by analyses of end-systolic wall tension and end-systolic wall stress.Conclusion:In confirmation of several previous studies, obesity was closely associated with an increase in blood pressure and left ventricular mass, and with early signs of disturbed left ventricular diastolic function. Left ventricular wall thickness and mass were well adapted to the increase in afterload; thus, we could not identify any non-afterload-dependent effect of an increase in BMI or waist: hip ratio on left ventricular hypertrophy.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To measure the magnitude and timing of seasonal variation of blood pressure and related factors in the elderly living in the community, and to assess their potential impact on cardiovascular risk.Design:Prospective study; from January 1991 to February 1992 blood pressure and other variables were measured at 2-monthly intervals in each subject in their own homes.Subjects:Ninety-six men and women, age range 65–74 years, recruited from a single group general practice in Cambridge.Main outcome measures:Seasonal variation of blood pressure, seasonal variation of prevalence of hypertension, seasonal variation of ambient temperature and body mass index.Results:Both systolic (SBP) and diastolic blood pressure (DBP) were greatest during the winter across the whole distribution of blood pressure. There was a fourfold increase in the proportion of subjects with blood pressures > 160/90 mmHg in winter compared with in summer. Regression analysis revealed highly significant seasonal differences in both SBP and DBP. After adjustment for confounding seasonal effects, a 1°C decrease in living-room temperature was associated with rises of 1.3 mmHg in SBP and 0.6 mmHg in DBP.Conclusions:Seasonal variation of blood pressure is heightened in older adults and may partly explain the greater cardiovascular disease mortality of elderly subjects during the winter. The blood pressures of elderly people may be inversely related to the ambient temperature. The public health implications of these findings deserve further investigation.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To assess the Accutracker II (version 30/23) ambulatory blood pressure monitor by nationally agreed protocols in order to resolve previous conflicting assessments, and to examine the feasibility of combining these protocols into one study.Design:The protocols of the Association for the Advancement of Medical Instrumentation (AAMI) and the British Hypertension Society (BHS) were used simultaneously.Subjects:Five normotensive subjects were used to assess interobserver variation; 30 subjects took part in the field evaluation and 85 in the laboratory evaluation. The latter subjects were selected to cover a wide range of blood pressures and differences in arm circumference.Outcome measurements:Classification of device accuracy according to the criteria of the BHS and AAMI protocols.Results:Among 255 observations the mean ±SD difference between blood pressure measurements by the Accutracker II and the observers was −2.2±0.8/ −3.5±0.9mmHg. There was a small but statistically significant difference between one device and the other two, but all three fulfilled the BHS criteria of 95% of measurements falling within 3 mmHg before and after use. In 30 24-h recordings >80% of the programmed inflations produced valid recordings. Editing criteria accounted for the majority (55%) of invalid readings; weak Korotkoff sounds, imperfect electrocardiogram signals or movement artefact accounted for the remainder.Conclusions:Version 30/23 of the Accutracker II fulfilled the AAMI criteria; using the BHS system, it was graded A for systolic and C for diastolic blood pressure. Although both protocols were readily combined into one study, they do not assess exactly the same aspects of blood pressure measurement. Previous conflicting evaluations could be due to differences in applying the protocols or may result from modifications in production models. Posture may affect the rating given by the BHS protocol. Until there is general international agreement on the method used to validate ambulatory blood pressure monitors, simultaneous use of both the BHS and AAMI protocols is recommended. In future assessments or investigational use of any similar instruments the model used should be described precisely.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To determine whether a microsatellite polymorphism of the insulin receptor gene (INSR) is associated with essential hypertension, as has been demonstrated previously for anRsalrestriction fragment length polymorphism (RFLP), and to examine blood pressure and plasma lipid profiles in relation to genotype.Design and methods:The study involved 75 Caucasian, non-diabetic hypertensive patients whose parents were both hypertensive, and 75 age-matched normotensive subjects whose parents were each normotensive after the age of 50 years. Genotypes for the microsatellite polymorphism were determined for each subject using leucocyte DNA and a polymerase chain reaction method. Other parameters, including pretreatment blood pressure, body mass index and plasma lipids, were also determined.Results:Comparison of microsatellite data for the eight genotypes and four alleles that were detected showed no significant difference by χ2analysis, either between the hypertensive and normotensive groups, or between obese and non-obese subgroups of hypertensives. This is in contrast to the significantly higher frequency seen for theR1- allele of anRsalRFLP ofINSR: 0.71 in the hypertensive group compared with 0.56 in the normotensive group.R1- allele frequency was elevated in all age groups of hypertensives and did not differ between obese and non-obese subgroups. The non-obese hypertensives also had different plasma lipid profiles according to genotypes of the RFLP, with higher total and low-density lipoprotein-cholesterol in patients having the hypertension-associatedR1- allele of the intron 9 polymorphism. Moreover, systolic blood pressure was significantly greater in patients carrying theR1- allele and aged ≤60 years.Conclusions:The present study allows definition of the hypertension-associated variants ofINSRas those which are in linkage disequilibrium with a (CA)-repeat insertion polymorphism in intron 9 of the large, 22 exon, >120-kb gene, but not those associated with a polymorphism in the second intron.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Objective:To delineate more precisely an operational threshold for making clinical decisions based on ambulatory blood pressure (ABP) measurement by studying the ABP in subjects who were diagnosed as either normotensive or hypertensive by conventional blood pressure (CBP) measurement.Subjects:Twenty-four research groups recruited 7069 subjects. Of these, 4577 were normotensive (CBP ≥140/90mmHg), 719 were borderline hypertensive (systolic CBP 141–159mmHg or diastolic CBP 91–94mmHg) and 1773 were definitely hypertensive. Of the subjects in the last of these categories, 1324 had systolic hypertension (systolic CBP ≤160 mmHg) and 1310 had diastolic hypertension (diastolic CBP ≤95 mmHg). Hypertension had been diagnosed from the mean of two to nine (median two) CBP measurements obtained at one to three (median two) visits.Results:The 95th centiles of the 24-h ABP distributions in the normotensive subjects were (systolic and diastolic, respectively) 133 and 82 mmHg. Of the subjects with systolic hypertension, 24% had 24-h systolic ABP <133 mmHg. Similarly, 30% of those with diastolic hypertension had 24-h diastolic ABP <82 mmHg. The probability that hypertensive subjects had 24-h ABP below these thresholds tended to increase with age and was two- to fourfold greater if the CBP of the subject had been measured at only one visit and if fewer than three CBP measurements had been averaged for establishing the diagnosis of hypertension. By contrast, for each 10-mmHg increment in systolic CBP, this probability decreased by 54% for 24-h systolic ABP and by 26% for 24-h diastolic ABP, and for each 5-mmHg increment in diastolic CBP it decreased by 6 and 9%, respectively.Conclusions:The ABP distributions of the normotensive subjects included in the present international database were not materially different from those in previous reports in the literature. One-fifth to more than one-third of hypertensive subjects had an ABP which was below the 95th centile of the ABP of normotensive subjects, but this proportion decreased if the hypertensive subjects had shown a higher CBP upon repeated measurement. The prognostic implications of elevated CBP in the presence of normal ABP remain to be determined.

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID

ISSN:0263-6352    

出版商:OVID    

年代:1993

数据来源: OVID