Reduction of left ventricular preload by lower body negative pressure alters Doppler transmitral filling patterns.

The objective of this study was to evaluate the effect of alterations in preload induced by lower body negative pressure on Doppler transmitral filling patterns. Echocardiograms and Doppler recordings were performed in 18 normal young men (aged 23 to 32 years) during various levels of lower body negative pressure (0, -20 and -50 mm Hg). Lower body negative pressure induced a reduction in diastolic velocity integral (from 12.17 +/- 0.79 to 8.42 +/- 0.71 cm, p = 0.0067) and consequently left ventricular diastolic diameter (from 5.11 +/- 0.09 to 4.45 +/- 0.1 cm, p less than 0.0001). There was a significant reflex increase in heart rate from 59.9 +/- 1.9 to 77.1 +/- 2.4 beats/min (p less than 0.0001), but blood pressure was unchanged. This reduction in preload altered Doppler transmittral filling patterns as follows: 1) peak early velocity (E) decreased from 59.2 +/- 3.8 to 39.1 +/- 1.7 cm/s (p less than 0.0001); 2) atrial filing velocity (A) was unchanged (35.58 +/- 1.5 to 33.52 +/- 1.4 cm/s, p = 0.517); 3) E/A ratio decreased from 1.7 +/- 0.13 to 1.19 +/- 0.08 (p = 0.0087); 4) mean acceleration (from 482 +/- 37 to 390 +/- 27 cm/s2, p = 0.03) and mean deceleration (from 327 +/- 31 to 169 +/- 21 cm/s2, p less than 0.001) of the early filling wave were significantly reduced; and 5) peak acceleration (from 907 +/- 42 to 829 +/- 29 cm/s2) and peak deceleration (from 771 +/- 94 to 547 +/- 76 cm/s2) also decreased, but not significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutrition and hypertension prevention.

Hypertension has been related to both obesity and a high salt intake. Evidence for the associations of blood pressure with body weight and dietary salt intake is summarized. In both adolescents and adults correlations between blood pressure and weight are highly significant, and in longitudinal studies change in blood pressure over time is correlated with change in weight. Correlations between salt intake and blood pressure are less striking, and the results of trials of modest salt restriction demonstrate a small but significant effect on blood pressure. Individuals vary in their susceptibility to salt, and hypertensive individuals are more responsive than normotensive individuals. Dietary deficiencies of potassium and calcium may amplify the effect of a high salt intake on blood pressure. Animal models provide compelling evidence for a genetic component to salt sensitivity of blood pressure. In two hypertension prevention trials, change in blood pressure was more convincingly related to change in weight than to change in dietary salt. Avoidance of obesity, or weight reduction in overweight individuals, should be key strategies for hypertension prevention. Avoidance of salt excess is also appropriate, although currently available trial data do not justify a recommendation of rigorous salt restriction for the entire population.

Suppression of adrenal mineralocorticoid production in prehypertensive young adult men.

We assessed the renin-aldosterone axis in response to treadmill exercise and adrenal steroidogenesis after graded ACTH infusions in two groups, each composed of nine young adult men from Bourbon County, Kentucky, from the upper and lower deciles of the blood pressure distribution. Those from the upper decile with relatively higher blood pressures, termed prehypertensive, had significantly lower plasma aldosterone and 18-hydroxycorticosterone concentrations after graded ACTH than those with relatively lower pressures, and had significantly lower urinary potassium excretions. Renin and aldosterone responses to exercise were also significantly blunted in the prehypertensive subjects. No differences were found in plasma cortisol, deoxycortisol, deoxycorticosterone, corticosterone, or dehydroepiandrosterone sulfate, although dehydroepiandrosterone was higher at one infusion rate in prehypertensives. These findings suggest that the adrenal mineralocorticoid pathway and the renin-aldosterone axis are suppressed in prehypertensive young males perhaps as an appropriate feedback response to their higher blood pressures.

Blood pressure trends with aging.

In industrialized societies, blood pressure increases with age, and blood pressure at one age is related to blood pressure at an earlier age. Blood pressure is also related to weight, weight change, and maturation. This paper reviews the association of growth and maturation with blood pressure and the evidence for blood pressure "tracking" with age. Additional longitudinal studies are required to determine if blood pressures before puberty are related to blood pressures of sexually mature young adults. Adolescents with "gestational" hypertension also have relatively high blood pressures at long-term follow-up. Thus, it may by possible to identify young individuals who are at increased risk for cardiovascular disease.

Correlates of adolescent blood pressure at five-year follow-up.

In 1973, standardized measurements of blood pressure (BP), height, and weight were obtained on all adolescents attending high school in a rural Kentucky county. In 1978, a 5-year follow-up BP study was undertaken of all adolescents who were 14-15 years old at the time of the initial survey (n = 310), and of selected 16-19 year olds who were in the high, intermediate, and low ranges of the initial sex-specific BP distributions (n = 198). Follow-up measurements included height, weight, and BP on all subjects and, in addition, overnight sodium (Na) excretion, serum cholesterol, glucose, triglyceride, and uric acid concentrations on the older group. Our findings indicate that BP in young adults is related to BP in adoleslcence, change in relative weight since adoleslcence, and current relative weight. Relative rank order of initial BP levels were maintained over the 5-year period in both the younger and older groups. Additional cardiovascular disease risk factors were found to cluster in young adults with high BP, and clustering of risk factors may, in part, be related to high relative weight.

Plasma renin activity, reactivity, concentration and substrate following hypertension during pregnancy. Effect of oral contraceptive agents.

Plasma renin activity is suppressed in approximately 25% of patients with essential hypertension, and the rate of in vitro angiotensin I production after addition of exogenous renin (renin reactivity) is increased in plasma of hypertensive patients. We have recently observed that blood pressure (116 +/- 1.5/68 +/- 1.7 mm Hg) of young women who had hypertension during a first pregnancy 3--6 years earlier (n = 63) was higher (p less than 0.005) than blood pressure (109 +/- 1.4/61 +/- 1.7 mm Hg) of women who remained normotensive during pregnancy (n = 52). To determine if alterations of the renin-angiotensin axis observed in patients with established hypertension also occur in young adults with relatively high blood pressure, plasma renin activity (PRA), plasma renin concentration (PRC), plasma renin substrate (PRS) and plasma renin reactivity (PRR) were compared in these two groups of subjects. Overall, PRA and PRC were inversely related to systolic blood pressure (p less than 0.02). Excluding women on oral contraceptive agents, the PRA response to standardized treadmill exercise was suppressed (less than 1.0 ng/ml/hr) in 19% of women with a history of hypertension during pregnancy and in no women who remained normotensive throughout a previous pregnancy; PRR did not differ (p greater than 0.8) in the two groups of young mothers (27.1 ng/ml/30 min +/- 1.2 SE VS 26.2 ng/ml/30 min +/- 0.9 SE). Thus, renin suppression, but not increased PRR, precedes the onset of hypertension. Oral contraceptive usage was associated with higher systolic blood pressures, increased PRS, and low PRC. Highest blood pressures and lowest PRA occurred in women with a history of hypertension during pregnancy who were taking oral contraceptive agents at the time of study.

Low renin in young mothers and their children following hypertension in pregnancy.

Young women who became pregnant as adolescents and developed hypertension during their first pregnancies had higher blood pressures than women who had remained normotensive throughout pregnancy. These young mothers served as subjects for a study to evaluate the relationship between different levels of "normal" blood pressure and renin-aldosterone. Overall, plasma renin activity (PRA), but not plasma aldosterone, was inversely related to systolic blood pressure both before (r = -0.28; p less than 0.003) and after (r = -0.24, p less than 1.01) treadmill exercise. Unrelated to blood pressure, PRA was also lower in blacks and in women using oral contraceptive agents (p less than 0.01). Of women with a history of hypertension in pregnancy, 30% (9 of 30) had low PRA after exercise. Low renin was associated with higher blood pressures. At the time of a second exercise test 3 years later, these women still showed elevated arterial pressure and low renin. PRA was also suppressed in the children of mothers with low renin, and there were significant correlations between maternal and child PRA (r = +0.55; p less than 0.003) and between maternal and child aldosterone (r = +0.60; p less than 0.001). In conclusion, low renin may be an appropriate response to higher arterial pressures, and within families may be a marker of "pre-hypertension."

Low renin-aldosterone in "prehypertensive" young adults.

PRA is suppressed in approximately 25% of patients with essential hypertension. To determine if renin suppression precedes the onset of hypertension, PRA and plasma aldosterone were measured before and after treadmill exercise in 129 young adults with relatively high, intermediate, or relatively low blood pressures sustained over 5 yr. PRA and aldosterone responses to exercise were lower (P less than 0.01) in the high blood pressure group. In contrast, plasma renin substrate was lower (P less than 0.01) in the low blood pressure group. Unrelated to blood pressure, PRA, but not aldosterone, was lower in black than in white subjects both before and after exercise. In conclusion, renin suppression precedes the onset of hypertension and may be an appropriate response to higher levels of arterial pressure.

Genetic determinants of hypertension: identification of candidate phenotypes.

Our long-term objective is to identify genes whose expression results in hypertension and in phenotypic changes that may contribute to hypertension. The purpose of the present study was to describe evidence for the heritability of hypertension-related phenotypes in hypertensive, hyperlipidemic black sib pairs. Outpatient anthropomorphic measurements were obtained in >200 affected sib pairs. In addition, 68 of these sib pairs were studied under controlled, standardized conditions at an inpatient clinical research center while off both antihypertensive and lipid-lowering medications. Heritability was estimated on the basis of sib-sib correlations and with an association model. Higher heritability estimates for blood pressure were observed with multiple measurements averaged over 24 hours than with measurements at a single time point, and heritability estimates for nighttime blood pressures were higher than those for daytime blood pressures. Heritability estimates for several of the phenotypes were augmented by obtaining measurements in response to a standardized stimulus, including (1) blood pressure responses to the assumption of upright posture, standardized psychological stress, and norepinephrine infusion; (2) plasma renin, aldosterone, epinephrine, and cAMP and cGMP responses to the assumption of upright posture; (3) para-aminohippurate and inulin clearances in response to norepinephrine infusion; and (4) plasma arginine vasopressin in response to NaCl infusion. High heritability estimates were also observed for various measures of body size and body fat, left ventricular size, cardiac index, stroke volume, total peripheral resistance, and serum concentrations of LDL and HDL cholesterol and leptin. These heritability estimates identify the hypertension-related phenotypes that may facilitate the identification of specific genetic determinants of hypertension in blacks with hyperlipidemia.

Baroreceptor sensitivity in prehypertensive young adults.

Decreased baroreceptor reflex sensitivity has been implicated in the pathogenesis of hypertension. The purpose of this study is to determine if alterations of baroreceptor function precede the development of hypertension in humans. Baroreceptor function was evaluated in 13 young adult white men with relatively high blood pressures sustained for 12 to 15 years and 12 age-matched men with sustained relatively low blood pressures. High pressure baroreceptor activity was evaluated by measuring change in pulse interval in response to decreases and increases of arterial pressure, induced by graded infusions of nitroprusside and angiotensin II, respectively. In response to both agents, baroreceptor slopes did not differ in the high and low blood pressure groups. Plasma norepinephrine also increased similarly in both blood pressure groups in response to nitroprusside. To study low-pressure baroreceptor function, responses to graded levels of lower-body negative pressure (LBNP) were measured. Comparing both blood pressure groups, there were similar increases of heart rate, total peripheral resistance, and plasma norepinephrine in response to LBNP. Both blood pressure groups also had similar increases of heart rate and blood pressure in response to isometric (handgrip) exercise. Thus, high-pressure and low-pressure baroreceptor function is not altered in prehypertensive young adults. However, continued follow-up will be required to determine if these individuals with sustained relatively high blood pressures are truly prehypertensive.

Diuretic therapies in low renin and normal renin essential hypertension.

This study was designed to compare the effectiveness of spironolactone, hydrochlorothiazide, and combined spironolactone-hydrochlorothiazide therapy in patients with low renin and those with normal renin essential hypertension. Patients with low renin hypertension had a greater hypotensive response to each regimen (p less than 0.001). Low renin patients responded equally to both spironolactone and to hydrochlorothiazide, and in low renin but not in normal renin patients reduction of blood pressure correlated with weight loss. These results suggest that a volume factor, not specifically related to increased mineralocorticoid production, contributes to the pathogenesis of low renin essential hypertension.

Dietary sodium and blood pressure: interactions with other nutrients.

This paper reviews the evidence that salt sensitivity of blood pressure is related both to the anion ingested with sodium as well as to other components of the diet. In several experimental models of salt-sensitive hypertension and in humans, blood pressure is not increased by a high sodium intake provided with anions other than chloride. Salt-induced increase of blood pressure depends on the concomitant ingestion of both sodium and chloride. Both epidemiologic and clinical evidence suggest that sodium chloride-induced increases of blood pressure are augmented by diets deficient in potassium or calcium. In experimental animals, a high intake of simple carbohydrates also augments sodium chloride sensitivity of blood pressure. These observations indicate that the effect of dietary sodium on blood pressure is modulated by other components of the diet.

Treatment of high blood pressure in the young.

Children with high normal or high BP should also be evaluated for other cardiovascular risk factors, and interventions should address overall cardiovascular risk. Nonpharmacologic interventions include weight reduction when appropriate, avoidance of dietary salt excess, and dynamic exercise. Drug treatment should be required in a minority of children with hypertension. There are concerns about the longterm effects of drug therapy on lipid and carbohydrate metabolism and on physical and cognitive growth and development. Beta adrenergic antagonists and diuretics are usually the first line drugs to be added to the nonpharmacologic therapeutic strategies for BP control in children. After a sufficient period of BP control, a stepped-down approach and discontinuation of drug therapy should be considered.

Blood pressure trends associated with changes in height and weight from early adolescence to young adulthood.

In children, blood pressure is more closely related to height and indices of maturation than to age. This study extends observations on the relationship between height, weight, maturation and blood pressure during early adolescence into young adulthood. Standardized measurements of blood pressure, height, and weight were initially obtained in all 14-15 year old adolescents (N = 304) in a rural Kentucky school system. Measurements were repeated 5 and 8 years later. Adolescents with relatively high blood pressures continued to have higher blood pressures as young adults. Increases in systolic and diastolic blood pressure over time were related to increases of relative weight in both sexes (p less than 0.0001 and p less than 0.005, respectively), and in males increases of systolic blood pressure were related to increases of height (p less than 0.005). However, males who attained their full height at younger ages had higher blood pressures both during adolescence and subsequently, as young adults. Thus blood pressure of young adults is related to blood pressure in adolescence, relative weight and change in relative weight since adolescence, and in males to age of maturation as determined by the age at which adult height is attained.

Planning for a community-based hypertension control program in the inner city.

Uncontrolled hypertension is a significant problem among African-Americans residing in inner city environments. To help address the problem, we are developing community-based hypertension control programs in African-American communities located in Milwaukee, Wisconsin and Chicago, Illinois. The Milwaukee program focuses on an entire, diverse inner city area, while the Chicago program is targeted to several more homogeneous African-American neighborhoods. The investigators hypothesize that the success of a hypertension control program will depend on carefully tailoring the educational approaches to the specific characteristics of the target area. Therefore, the study areas that have been selected differ with regard to community size and diversity, community 'stressors' (poverty, unemployment, crime, etc), and types of organizations which are present in the community. This paper describes the background and the rationale for community hypertension control programs in the inner city. The initial approaches to establishing the program by developing interfaces with the community and the gathering of baseline data through household surveys are described.

The use of itemized register tapes for analysis of household food acquisition patterns prompted by children.

This article describes a method of collecting and analyzing itemized grocery receipts for use in epidemiological studies. As part of a larger study of children's food acquisition and exercise habits related to cardiovascular disease, a sample of 50 families was asked to keep itemized grocery receipts for a 2-week period. To control for bias as a result of differences in food consumption and food acquisition, mothers were asked to log meals eaten away from home, food used from home production, and gifts of foods. Items on the receipts were coded according to food groups and whether they represented child-prompted purchases. The items were expressed in terms of the percentage of the food dollar each category represented. Data from the survey were compared with data collected in national surveys. The method was found to be relatively non-intrusive, easily carried out, and eliminated many of the problems associated with non-response, respondent burden, and recall characteristic of other food account methods. It is suggested as a feasible way of characterizing the family food environment in epidemiological studies.

Incorporating socio-economic and risk factor diversity into the development of an African-American community blood pressure control program.

OBJECTIVE: To develop culturally competent community based blood pressure control programs for inner-city African Americans. DESIGN: Cross sectional study of randomly selected households from three experimental and three control communities. SETTING: Very low, moderately low and moderate socio-economic status (SES) inner-city communities in Chicago, Illinois. PARTICIPANTS: 957 African Americans adults, aged 18 and over from target communities. MAIN OUTCOME MEASURE: Household health assessments included employment, education and other demographic information, history of hypertension, disease prevalence, health behaviors, risk factor prevalence, stress, coping/John Henryism, social support, health care utilization and standardized assessments of blood pressure, height, and weight. RESULTS: There were no significant gender differences in blood pressure levels. Men had more hypertension than women, and women in the very low SES community had significantly more hypertension than women in the moderately low SES community. There was significantly more hypertension overall in the moderately low SES community. Age, education and BMI were the only factors significantly associated with systolic and diastolic blood pressure in all three communities. The very low SES community had significantly more obesity and more uninsured persons than the other communities. CONCLUSIONS: Intraracial diversity is an important factor to be considered in the development of community blood pressure control programs for African Americans. Age, gender, educational background and SES play a major role in influencing health behaviors and access to health care.

Effect of relative weight on familial blood pressure aggregations.

Because of recognized associations between body build and blood pressure in individuals, along with familial clustering of these variables, a study was undertaken to determine whether parent-child blood pressure resemblances reflect parent-child similarities in body build. Adolescents were selected to serve as propositi for the parental study from a large school population. To maximize the liklihood of demonstrating existing associations between blood pressure and the body build in family members, blood pressures and weight status of parents whose adolescent children had high blood pressures (Group I parents) were compared with similar observations in parents whose children had low blood pressures (Group II parents). Group III adolescent propositi were selected for high weight status but blood pressure below the mean for their sex group. Group I parents had higher blood pressures and body weight than did Group II parents, similar to the differences in the groups of children. Parents of Group III propositi had high body weight but blood pressure that was intermediate between the other two parent groups. Differences in Group I and III parental blood pressures, despite similar body weights, suggest that familial blood pressure resemblances cannot be solely attributed to familial similarities in body weight.