Aortic pressure-only wave separation analysis in adolescents: accuracy and associations with left ventricular mass index.

Early-life exposure to high blood pressure (BP) is associated with cardiovascular target organ damage but not all BP-related risk is attributable to systolic and diastolic BP alone. In adolescence, aortic wave separation (WS) parameters are associated with increased left ventricular mass index (LVMI) but this approach is limited by the requirement for aortic flow measurements. Several methods for estimating the aortic flow waveform from pressure waveforms have emerged, but their accuracy and associations with LVMI have never been tested in adolescents, which was the aim of our study. Carotid pressure waveforms were acquired by tonometry from 58 adolescents (age 16 ± 1.5 years, 59% female). Measured (aortic) flow and LVMI were acquired via 2D echocardiography. Three pressure-only approximations of aortic flow were synthesized, including triangular, excess, and individualized-physiologic flow. A 4th aortic flow (average flow) was approximated from the average of all 58 measured flow waveforms. Forward (Pf) and backward (Pb) pressure and reflection magnitude (Rm) were derived from WS analysis. The individualized-physiologic flow produced the best approximations of Pf (mean difference ± SD, -0.15 ± 2.38 mmHg), Pb (0.14 ± 0.25 mmHg), and Rm (0.01 ± 0.02 mmHg). Pf derived using measured, individualized-physiologic, and average flow, was similarly associated with LVMI adjusting for age, brachial systolic BP, cardiac output, and BMI (P ≤ 0.03 all). Pb derived using all flow waveforms was associated with LVMI and all associations yielded similar effect estimates. Of the estimated flow waveforms, individualized-physiologic flow yielded the best approximation of WS parameters and may provide important physiological and clinical insight among adolescents.

Inactive Matrix Gla Protein, Arterial Stiffness, and Endothelial Function in African American Hemodialysis Patients.

BACKGROUND: Matrix Gla protein (MGP) is a vascular calcification inhibitor dependent upon vitamin K for activation. Evidence suggests that elevated plasma inactive MGP levels (desphospho-uncarboxylated MGP, dp-ucMGP; indicating poorer vascular vitamin K status) are associated with greater cardiovascular disease (CVD) risk. Despite African Americans experiencing highest rates of kidney failure and CVD events, relationships between dp-ucMGP and CVD risk markers have not been examined in this population. We investigated vascular vitamin K status (via plasma dp-ucMGP) between African American hemodialysis (HD) patients and healthy controls, and the associations of dp-ucMGP with arterial stiffness and endothelial function in HD patients only. METHODS: In 37 African American HD patients and 37 age- and race-matched controls, plasma dp-ucMGP was measured by enzyme immunoassay as a marker of vascular vitamin K status. Carotid-femoral pulse wave velocity (PWV; arterial stiffness measurement) and brachial artery flow-mediated dilation (FMD; endothelial function measurement) were assessed by applanation tonometry and ultrasound, respectively, in HD patients only. RESULTS: Mean dp-ucMGP levels were 5.6 times higher in HD patients vs. controls (2,139 ± 1,102 vs. 382 ± 181 pmol/l, P < 0.01). Multiple linear regression, adjusting for age, sex, dialysis vintage, diabetes mellitus, CVD history, body mass index, and blood pressure, revealed that dp-ucMGP was independently related to PWV (standardized ß = 0.49) and FMD (standardized ß = -0.53) (both P < 0.01). CONCLUSIONS: Our data suggest that the higher plasma dp-ucMGP concentrations found in African American HD patients may be associated with greater arterial stiffness and endothelial dysfunction.

Abnormal Central Pulsatile Hemodynamics in Adolescents With Obesity: Higher Aortic Forward Pressure Wave Amplitude Is Independently Associated With Greater Left Ventricular Mass.

We hypothesized that increased aortic forward pressure wave amplitude (Pf), which is determined by characteristic impedance (Zc) in the proximal aorta, is the primary hemodynamic determinant of obesity-associated higher left ventricular (LV) mass in adolescents. Aortic pulsatile hemodynamics were measured noninvasively in 60 healthy adolescents (age 14-19 years; 42% male; 50% black) by sequential recordings of pulse waveforms via tonometry, brachial blood pressure, and pulsed Doppler and diameter of the LV outflow tract using 2-dimensional echocardiography. Adolescents who were overweight/obese (n=23; age 16.0±0.3 years; body mass index ≥85th percentile) had higher LV mass index, brachial and carotid systolic blood pressure and pulse pressure, normalized Zc and Pf compared with adolescents with healthy weight (n=37; 16.7±0.3 years; body mass index <85th percentile, all P<0.01). In contrast, there was no difference in mean or diastolic blood pressure, carotid-femoral pulse wave velocity, carotid augmentation index, or aortic backward wave amplitude (all P>0.05). Stepwise multiple linear regression analysis that included age, sex, race, normalized Zc, and brachial systolic blood pressure revealed that body mass index (B±SE; 0.49±0.20, P=0.02, R2=0.26), aortic Pf (0.22±0.07; P<0.02, R2 change=0.11), and cardiac output (2.82±1.02, P<0.01; R2 change=0.08) were significant correlates of LV mass index (total R2=0.44, P<0.01). These findings suggest that higher aortic Pf is a major hemodynamic determinant of increased LV mass in adolescents with elevated adiposity. Improper matching between aortic diameter and pulsatile flow during early systole potentially contributes to the early development of LV hypertrophy in childhood obesity.

Brain natriuretic hormone predicts stress-induced alterations in diastolic function.

BACKGROUND: Mental stress (MS) reduces diastolic function (DF) and may lead to congestive heart failure with preserved systolic function. Whether brain natriuretic hormone (brain natriuretic peptide [BNP]) mediates the relationship of MS with DF is unknown. METHODS: One hundred sixty individuals aged 30 to 50 years underwent 2-hour protocol of 40-minute rest, videogame stressor and recovery. Hemodynamics, pro-BNP samples and DF indices were obtained throughout the protocol. Separate regression analyses were conducted using rest and stress E/A, E' and E/E' as dependent variables. Predictor variables were entered into the stepwise regression models in a hierarchical fashion. At the first level, age, sex, race, height, body mass index, pro-BNP and left ventricular mass (LVM) were permitted to enter the models. The second level consisted of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). The final level contained cross-product terms of race by SBP, DBP and HR. RESULTS: E/A ratio was lower during stress compared to rest and recovery (P < 0.01). Resting E/A ratio was predicted by a regression model of age (-0.31), pro-BNP (0.16), HR (-0.40) and DBP (-0.23) with an R² = 0.33. Stress E/A ratio was predicted by age (-0.24), pro-BNP (0.08), HR (-0.38) and SBP (-0.21) with total R² = 0.22. Resting E' model consisted of age (-0.22), pro-BNP (0.26), DBP (-0.27) and LVM (-0.15) with an R² = 0.29. Stress E' was predicted by age (-0.18), pro-BNP (0.35) and LVM (-0.18) with an R² = 0.18. Resting E/E' was predicted by race (0.17, B > W) and DBP (0.24) with an R² = 0.10. Stress E/E' consisted of pro-BNP (-0.36), height (-0.26) and HR (-0.21) with an R² = 0.15. CONCLUSIONS: pro-BNP predicts both resting and stress DF, suggesting that lower BNP during MS may be a marker of diastolic dysfunction in apparently healthy individuals.

Adverse childhood experiences are associated with detrimental hemodynamics and elevated circulating endothelin-1 in adolescents and young adults.

Growing evidence suggests that adverse childhood experiences (ACEs) increase the risks for coronary heart disease and hypertension in mid and late adulthood. We previously reported that early life stress induces a hyperreactive endothelin-dependent cardiovascular phenotype in a rat model. In the present study, we evaluated whether exposure to ACEs is associated with greater peripheral resistance, arterial stiffness, blood pressure, or elevated circulating endothelin-1 levels in humans. In 221 healthy adolescents and young adults (mean age, 21 years; range, 13-29 years), we found a graded association of ACE exposure with plasma endothelin-1 levels, of which on average 18% and 24% were higher in participants with 1 ACE and ≥2 ACEs, respectively, compared with those with no ACEs (P=0.001). Participants with moderate/severe exposure to ACEs (≥2 ACEs) had significantly higher total peripheral resistance index (+12%), diastolic blood pressure (+5%), and pulse wave velocity (+9%) compared with those who were not exposed. These associations were independent of age, race, sex, body mass index, and childhood socioeconomic status. Our results indicate that early life stress promotes cardiovascular disease risk, specifically detrimental vascular and cardiac function, detectable in young adulthood.

Aldosterone contributes to elevated left ventricular mass in black boys.

BACKGROUND: Left ventricular hypertrophy (LVH) poses a great risk of cardiovascular morbidity and mortality in adults and may pose a serious risk in children. Adult studies have shown that renin-angiotensin-aldosterone system (RAAS) levels directly correlate with left ventricular mass index (LVMI). The purpose of this study is to explore race- and sex-related effects of the RAAS on LVMI in adolescents. METHODS: Data were collected from a sample of 89 blacks (44 girls, 45 boys) and 102 whites (40 girls, 62 boys) aged 15-19. Data collected included sex, age, body mass index (BMI), LVMI, baseline blood pressure, and levels of aldosterone and angiotensin II. RESULTS: In black males, increased aldosterone levels correlated with decreased sodium excretion (r= -0.336, p=0.024), increased blood pressure (r=0.358, p=0.016), and increased LVMI (r=0.342, p=0.022). In black females, increased aldosterone levels correlated with increased baseline blood pressure (r=0.356, p=0.018). In white males, increased aldosterone correlated with decreased sodium excretion (r= -0.391, p=0.002). In white females, aldosterone levels correlated with increased baseline blood pressure (r=0.323, p=0.042) and decreased sodium excretion (r= -0.342, p=0.031). CONCLUSIONS: The results suggest the following model in black males: increased aldosterone leads to increased sodium retention, causing a volume-mediated increase in blood pressure; increased blood pressure results in increased left ventricular mass, and eventually LVH.

Stress reduces diastolic function in youth.

OBJECTIVE: Research regarding the influence of mental stress (MS) on heart function focused primarily on heart contractility. We hypothesized that MS results in attenuated diastolic function (DF) as early as in adolescence and this effect may differ by race and sex. METHODS: 161 normotensive adolescents (81 blacks and 80 females) performed resting (control) and MS (experimental) conditions on separate visits. Visits lasted for 3 hours (1-hour rest, video game challenge and recovery for experimental visit. Mitral inflow early (E) to late (A) filling velocities (E/A) ratio; mitral valve annular early velocity (E') and E/E' ratio were recorded every 30 minutes to evaluate DF. RESULTS: BP and HR increased during experimental visit (all p values < .01). E/A ratio progressively increased during control visit (mean [SE], from 1.93 ± 0.42 to 2.01 ± 0.47) but decreased during the stress phase of experimental visit (from 1.91 ± 0.44 to 1.87 ± 0.50, p interaction < .001). In white males, E' increased from rest to stress phase (from 10.3 ± 2.55 to 10.7 ± 2.28 cm/s), whereas E' decreased in white females (from 11.0 ± 2.62 to 10.6 ± 2.53 cm/s), black males (from 10.5 ± 2.31 to 9.9 ± 2.19 cm/s), and black females (from 10.6 ± 2.22 to 10.3 ± 1.86 cm/s, p interaction < .04). During stress, higher A was associated with higher E/E' ratio. CONCLUSIONS: Recurrent episodes of mental stress may increase the risk of poor DF, and these adverse effects may be stronger in females and black males.

Impact of transcendental meditation on left ventricular mass in african american adolescents.

Background. An early sign of ventricular remodeling is increased left ventricular mass (LVM) which over time may lead to left ventricular hypertrophy, the strongest predictor of cardiovascular morbidity and mortality, other than advancing age. Methods. 62 (30 TM; 32 CTL) African American adolescents (age 16.2 ± 1.3 years) with high normal systolic BP were randomly assigned to either 4-month Transcendental Meditation (TM) or health education control groups. The echocardiographic-derived measure of LVM index (LVMI = LVM/ht(2.7)) was measured before and after the 4-month TM study and at 4-month followup. 2D-guided M-mode echocardiography using a Hewlett Packard 5500 echosonograph was used to determine LVMI. Results. The TM group exhibited a greater decrease in LVMI at 4-month followup compared to the CTL group (-2.6 versus +0.3 gm/ht(2.7), P < 0.04). The TM group exhibited a lesser increase in BMI at 4-month follow-up compared to the CTL group (0.2 ± 1.6 versus 1.1 ± 1.4, P < 0.03). Conclusion. These findings indicate that among a group of prehypertensive African American adolescents, 4 months of TM compared to heath education resulted in a significant decrease in LVMI, and these changes were maintained at 4-month follow-up.

Does the relationship between natriuretic hormones and diastolic function differ by race?

INTRODUCTION: Heart failure develops earlier and is more prevalent in blacks than whites because of their higher incidence of hypertension and diabetes and likely subsequent diastolic dysfunction. Natriuretic peptides (NP) prevent cardiac malfunction through pressure, natriuresis action. However, whether race affects the relationships of NP action with cardiac function is unknown. METHODS: To assess this, 55 (21 whites and 27 males) normotensive adults underwent a 2-hour protocol of 40 minutes rest, video game stressor and recovery. Mitral inflow and myocardial velocities (tissue Doppler) were recorded every 20 minutes. Blood pressure and heart rate were obtained at 10-minute intervals. Blood samples for pro-atrial NP and pro-brain NP (pro-BNP) were collected every 40 minutes. RESULTS: There were differences in the association between (1) the changes from rest to stress for E/A ratio and double product (whites, r = -0.42; blacks, r = 0. 10; P = 0.034 for difference between correlations); (2) stress E(m) and pro-atrial NP (whites, r = 0.59; blacks, r = -0.25; P = 0.025); (3) rest E(m) and BNP (whites, r = 0.83; blacks r = -0.17; P = 000); (4) rest E(m)/A(m) and pro-BNP (whites, r = 0.70; blacks, r = -0.42; P = 0.003); (5) rest E/E(m) and pro-BNP (whites, r = -0.61; blacks, r = 0.31; P = 0.015) and (6) stress E and pro-BNP (whites, r = 0.56; blacks, r = -0.18; P = 0.043). CONCLUSION: The higher correlations between levels of NP and diastolic function indices both at rest and stress suggest that NP protective action is more pronounced in whites than in blacks.

Stress-induced sodium retention and hypertension: a review and hypothesis.

Hypertension--an important health problem in industrialized nations--is particularly significant in blacks and obese individuals, in whom it is hypothesized to result from impaired renal sodium regulation. We reviewed studies that identified individuals with impaired sodium regulation by examining the natriuretic response to mental stress. A significant percentage of black and obese individuals retain or have a diminished natriuretic response to mental stress despite increased blood pressure (BP). This contributes a volume component to the normal resistance-mediated BP increase, and BP remains elevated after the stressor ceases until the volume expansion diminishes. The stress exposes these individuals to greater cardiovascular load. This response pattern has been linked to renin-angiotensin-aldosterone system activity, and is associated with premature target-organ damage. Assessing stress-induced sodium retention provides a method to identify patients with impaired sodium regulation without using a dietary protocol that poses adherence difficulties, or complicated laboratory assessments. Furthermore, research using this technique indicates the effectiveness of renin-angiotensin-aldosterone system blockers in correcting impaired sodium regulation and consequent hypertension in these individuals.

Change of genetic determinants of left ventricular structure in adolescence: longitudinal evidence from the Georgia cardiovascular twin study.

BACKGROUND: Genetic contribution to left ventricular (LV) structure is generally recognized, but whether and how this influence varies by ethnicity or with age is unknown. METHODS: Participants were 517 European-American (EA) and African-American (AA) twin pairs (mean age: 14.6 +/- 3.0) at visit 1 and 422 EA and AA twin pairs at follow-up 4.1 years later. Echocardiograms were obtained on both visits. Data were analyzed using the structural equation modeling software Mx. RESULTS: Body mass index (BMI) was a strong predictor for all LV measures at both visits 1 and 2, accounting for 3.5-24.2% of the total variance. Hemodynamics explained up to 4.5% additional LV measures variance. After adjusting for BMI, LV measures showed substantial heritability (range: 21-71%). Best-fitting longitudinal models revealed considerable novel genetic effects on the interventricular septum, posterior wall-, and relative wall thickness (RWT) (but not LV internal diameter), accounting for 32-41% of the phenotypic variance at visit 2, with no significant gender and ethnic effects. There was a gender difference for LV mass index in AAs (P < 0.01), with a significant influence of novel genetic effects in males (47%), but not in females. No gender difference was seen in EAs, with 34% of the phenotypic variance at visit 2 attributable to novel genetic effects. CONCLUSIONS: The heritability of cardiac structure and geometry was equally substantial in both AAs and EAs. Significant novel genetic influences were detected for all measures but LV inner diameter and LV mass index in AA females. Further developmental genetic studies are warranted to elucidate the nature of the emerging gene effects during the transition from adolescence to adulthood.

The association of race and sex to the pressure natriuresis response to stress.

OBJECTIVE: Sympathetic nervous system activation promoting sodium retention has long been recognized to play a significant role in the development and maintenance of salt-sensitive hypertension. The purpose of this study was to examine the influence of race and sex on the pressure natriuresis response to prolonged behavioral stress in youth. METHODS: The 190 subjects included 94 boys (41 African American, 53 Caucasian) and 96 girls (44 African American, 52 Caucasian) of similar age (17-19 years). The stress test was composed of a one hour competitive video game task preceded and followed by two-hour rest periods. Blood pressure (BP) was obtained at 15 minute intervals and sodium excretion (U(Na)V) was measured hourly. The general linear model was used to model the effects of race, sex, and their interaction on the variables of interest. RESULTS: Caucasians, compared to African Americans, had a greater change in U(Na)V (F[1,183] = 5.28, P = .0227), as did boys compared to girls (F[1,183] = 5.72, P = .0178), with no interaction between race and sex. The race-by-sex interaction was significant for the change in systolic BP (F[1,183] = 5.66, P = .0184), with Caucasian girls showing a smaller change than the other three race/sex groups. CONCLUSION: African Americans have a reduced natriuretic response to stress, which may be a marker or mechanism for the development of salt-sensitive hypertension in this population. The race difference within girls is of interest and requires further investigation.

Heritability of arterial stiffness in black and white American youth and young adults.

BACKGROUND: Our objectives were to examine the heritability of arterial stiffness measured as pulse-wave velocity (PWV), and its dependence on ethnicity, gender, and blood pressure (BP). METHODS: As part of the Georgia Cardiovascular Twin Study, we measured aorto-radial (radial) and aorto-dorsalis-pedis (foot) PWV in 702 twins (41% black; 49% male) aged 12 to 30 years (mean age, 17.7 +/- 3.3 years), including monozygotic and dizygotic pairs of the same as well as opposite gender. Ethnicity and gender effects on genetic and environmental contributions to PWV were estimated by genetic model fitting. RESULTS: Diastolic BP was the most important hemodynamic predictor. The best-fitting models showed no ethnicity or gender differences in estimates of genetic and environmental influence, and indicated substantial heritabilities of 0.43 (95% confidence interval, 0.30 to 0.54) and 0.53 (95% confidence interval, 0.42 to 0.62) for radial and foot PWV, respectively. Over a quarter of these heritabilities (0.19 for radial PWV; 0.14 for foot PWV) could be attributed to genes that also influenced diastolic BP, as based on multivariate models. CONCLUSIONS: Individual differences in the arterial stiffness of youth and young adults are substantially heritable, and >25% of this heritability is explained by genes that also influence diastolic BP. Heritability estimates do not show any differences between blacks and whites or males and females.

Relationship of visceral adiposity to cardiovascular disease risk factors in black and white teens.

OBJECTIVE: We tested the hypothesis that visceral adiposity, compared with general adiposity, would explain more of the variance in cardiovascular disease (CVD) risk factors. RESEARCH METHOD AND PROCEDURES: Subjects were 464 adolescents (238 black and 205 girls). Adiposity measures included visceral adipose tissue (VAT; magnetic resonance imaging), percent body fat (%BF; DXA), BMI, and waist girth (anthropometry). CVD risk factors were fasting insulin, fibrinogen, total to high-density lipoprotein-cholesterol ratio, triglycerides (TGs), systolic blood pressure, and left ventricular mass indexed to height2.7. RESULTS: After adjustment for age, race, and sex, all adiposity indices explained significant proportions of the variance in all of the CVD risk factors; %BF tended to explain more variance than VAT. Regression models that included both %BF and VAT found that both indices explained independent proportions of the variance only for total to high-density lipoprotein-cholesterol ratio. For TGs, the model that included both %BF and VAT found that only VAT was significant. For systolic blood pressure and left ventricular mass indexed to height2.7, anthropometric measures explained more of the variance than VAT and %BF. DISCUSSION: The hypothesis that visceral adiposity would explain more variance in CVD risk than general adiposity was not supported in this relatively large sample of black and white adolescents. Only for TGs did it seem that VAT was more influential than %BF. Perhaps the deleterious effect of visceral adiposity becomes greater later in life as it increases in proportion to general adiposity.

Vascular endothelium summary statement II: Cardiovascular disease prevention and control.

The prevention and control of cardiovascular disease (CVD), principally ischemic heart disease and stroke, are a major clinical and public health challenge. Worldwide, CVD accounts for substantial morbidity and mortality. The major modifiable CVD risk factors are known and all of them cause endothelial activation and dysfunction. Preventing and controlling the established risk factors are associated with preserved endothelial function and reduced risk of CVD. Research advances that improve our understanding of strategies to preserve endothelial function or make the endothelial cells resilient to environmental insults may help improve our preventive interventions. This summary statement addresses the current state of the science with respect to endothelial dysfunction and CVD pathogenesis, diagnostic evaluation, and suggested strategies for public health practice and research.

Early markers of cardiovascular disease.

Vascular endothelium function plays a pivotal role in cardiovascular pre-clinical markers. Nitric oxide secreted by the vascular endothelium has a vasodilatory effect that reduces blood pressure which, in turn, prevents increases of left ventricular mass and intima-media thickness and improves left ventricular relaxation. Modern ultrasound technique allows noninvasive assessment of endothelial function and permits identification of functional alteration prior to manifestation of anatomical changes in the cardiovascular system. However, effort is needed to improve the reliability and reproducibility of ultrasound derived measure of endothelial function. This article provides an overview of challenges of clinical determination of endothelium-dependent arterial dilatation. In addition, we highlight the necessity of targeting the pediatric population in studies aimed at preventing and treating cardiovascular disease.

Gender influences endothelial-dependent arterial dilatation via arterial size in youth.

BACKGROUND: Reduced endothelial-dependent arterial dilatation (EDAD) has been suggested as an early marker of arteriosclerosis, since it has been reported to correlate with known cardiovascular disease (CVD) risk factors. It is unclear, however, whether gender plays a mediating or a moderating role in these relationships. The aim of this study was to evaluate the influence of gender on EDAD in youth at risk for CVD. METHODS: The sample population of 261 individuals (mean age, 20 yr; SD, 3 yr) consisted of 148 African Americans, 113 European Americans, 133 males, and 128 females, all with a verified family history of CVD (ie, hypertension, myocardial infarction). Anthropometrics, sociometrics, hemodynamics, brachial artery diameter, left ventricular mass, and relative wall thickness were measured and used as independent variables. EDAD (dependent variable) was expressed as percent (%) change of brachial artery diameter to reactive hyperemia induced by pressure cuff occlusion and release. Artery diameters were calculated via an automated border detection system. RESULTS: Percent EDAD change was inversely related to initial diameter of the brachial artery. Mean percent EDAD change was 14.37% for female subjects compared with 10.48% for male subjects. The gender difference was a function of smaller initial artery size in the female subjects. When initial diameter and gender were considered simultaneously within a multivariate model, the gender effect was eliminated. Although a large prediameter effect remained, the relationship between prediameter and EDAD was greater in female than in male subjects (ie, interaction/moderating effect). CONCLUSION: The data suggest that the smaller the artery is, the more it will dilate. Further EDAD investigations are needed to predict arteriosclerosis, taking into account of the gender difference in vessel size.

Adiposity is related to gender differences in impaired stress-induced pressure natriuresis.

The purpose of this study was to determine if there are gender differences in stress-induced pressure natriuresis and to examine the effects of adiposity on these differences. The subjects were 151 boys and 141 girls 15 to 18 years of age who underwent a 5-hour stress protocol (2-hour prestress, 1-hour stress, 2-hour poststress) after being brought into similar levels of sodium balance. The gender-by-condition interaction was significant for systolic and diastolic blood pressure (P=0.001 for both), and the effect of condition was significant for sodium excretion (P=0.001). Systolic blood pressure was higher for boys throughout the protocol (P=0.001 for each) and correlated with body mass index at each condition (range in r=0.28 to 0.35; P<0.001 for each). Hemodynamically, in boys body mass index was correlated with cardiac output during stress (r=0.23; P=0.006), which was correlated with systolic blood pressure (r=0.21; P=0.01). With respect to natriuresis, body mass index was inversely correlated with sodium excretion during stress (r=-0.22; P=0.008) and positively correlated with angiotensin II in a subsample of boys (n=89: r=0.31; P=0.003). The inverse correlation between angiotensin II and sodium excretion during stress approached significance (r=-0.17; P<0.06). Similar results were not observed for girls. In conclusion, gender differences in stress-induced pressure natriuresis appear to be related to the influence of adiposity on both blood pressure and natriuresis.

Impaired stress-induced pressure natriuresis increases cardiovascularload in African American youths.

BACKGROUND: We hypothesized that impaired stress-induced pressure natriuresis increases blood pressure (BP) load. METHODS: The 118 African American youths were brought into similar levels of sodium balance. The protocol consisted of a 2-h baseline period, a 1-h stress period (competitive video games), and a 2-h recovery period. RESULTS: Normal pressure natriuresis (n = 80) resulted from a resistance-mediated (r = 0.23; P <.03) increase in BP (P <.001). In contrast, impaired pressure natriuresis (n = 38), leading to an extended period of elevated BP (P <.05), resulted from a volume-mediated (r = 0.55; P <.002) increase in BP (P <.001). CONCLUSIONS: Impaired stress-induced pressure natriuresis may contribute to the development of essential hypertension, particularly in African Americans.

Plasma endothelin-1 release during acute stress: role of ethnicity and sex.

OBJECTIVES: The purposes of this study were to examine possible ethnic and sex differences in plasma ET-1 levels at rest and in response to acute stress and to examine relationships between ET-1 and vasoconstrictive-mediated BP reactivity to stress. METHODS: Two hundred twenty-two adolescents (mean age = 18.5 +/- 2.8 years; 130 [70 males] EAs and 92 [48 males] AAs) completed two stressors (video game, forehead cold). Hemodynamic measures and blood samples were collected at catheter insertion and before and immediately after the two stressors, separated by 20-minute rest periods. RESULTS: AAs and males exhibited higher levels of SBP and DBP and of TPRI and ET-1 at each sampling point compared with EAs and females, respectively (p values <.001). AAs and males exhibited greater increases in SBP, TPRI, and ET-1 in response to each stressor (p values <.05). Intraindividual correlations between ET-1 and hemodynamic parameters revealed that most individuals exhibited a positive association between ET-1, BP, and TPRI. However, some individuals exhibited a negative association between ET-1 and the above-mentioned hemodynamics, suggesting a compensatory vasodilation mechanism. CONCLUSION: The findings demonstrate significant sex and ethnicity differences in stress-induced vasoconstrictive peptide release and support the hypothesis that these differences may be important in explaining the ethnicity and sex differences in the prevalence of cardiovascular disease.