Predictors of future ambulatory blood pressure in youth

Primary hypertension and special aspects of hypertension in older children and adolescents

The prevalence of hypertension has increased at an accelerated rate in older children and adolescents. This has raised great concern about premature development of cardiovascular disease, which has major long-term health and financial implications. While obesity and sedentary habits largely explain this phenomenon, there are other social and cultural influences that may unmask genetic susceptibility to hypertension in the pediatric population. While it is essential to exclude numerous causes of secondary hypertension in every child, these disorders are not discussed in this review. Rather, the aim of this review is to familiarize pediatricians with casual and ambulatory blood pressure measurement, epidemiology, pathophysiology, and management of several common conditions that play a role in the development of hypertension in children and adolescents. Besides primary hypertension and obesity-related hypertension, emphasis is given to epidemiology, measurement of blood pressure, including ambulatory blood pressure monitoring, hypertension associated with drug use, teenage pregnancy, and video and computer games. Lastly, because pediatricians are increasingly confronted with special issues concerning the management of the hypertensive athlete, this topic is also addressed.

Cardiovascular effects in adolescents while they are playing video games: a potential health risk factor?

We analyzed heart rate (HR), systolic and diastolic blood pressure (SBP, DBP), oxygen consumption, and carbon dioxide production in 17 male adolescents during a racing simulation video game (VG) and compared to resting state (RS) and exercise testing (ET) measures. We were able to demonstrate a significant (p<.005) increase from RS to VG concerning HR (+13.1 bpm), SBP (+20.8 mmHg), and DBP (+12.1 mmHg) with SBP and DBP elevations exceeding 2 SD in all children and 14/17 children, respectively. The energy consumption during VG (max 1.71 kcal/min) was unaltered compared to RS and significantly lower compared to ET even at the starting strain of 25 W (1.94 kcal/min). Hemodynamic parameters tested demonstrated lower HR, unchanged SBP, and higher DBP during the VG compared with ET. Comparing all measured parameters it can be said that the relation of blood pressure and energy consumption during VG might not be favorable.

Temporal stability of twenty-four-hour ambulatory hemodynamic bioimpedance measures in African American adolescents

BACKGROUND

The reliability of ambulatory impedance cardiography has not been evaluated.

OBJECTIVE

The purpose of this study was to determine the reproducibility of daytime and night-time ambulatory bioimpedance-derived measures of hemodynamic function in youth.

METHODS

Thirty-five African American adolescents (ages 16.2+/-1.4 years, 14 girls, 21 boys) with high normal systolic resting blood pressure (BP) were evaluated twice, separated by a 2-month interval. Measures were collected using the AIM-8-V3 Wearable Cardiac Performance Monitor (Bio-impedance Technology, Inc., Chapel Hill, North Carolina, USA) and the Spacelabs ambulatory BP monitor 90207 (Spacelabs Inc., Redmond, Washington, USA) from 0600 h to midnight every 20 min and from midnight to 0600 h every 30 min in the natural environment.

RESULTS

There were no significantly different means (P>0.15) between the two visits for daytime ambulatory heart rate (HR, r = 0.81), stroke volume (SV, r = 0.54), cardiac output (CO, r = 0.56), pre-ejection period (PEP, r = 0.59), left ventricular ejection time (LVET, r = 0.74), Heather Index (HI, r = 0.79), systolic BP (SBP, r = 0.79), diastolic BP (DBP, r = 0.66), mean arterial pressure (MAP, r = 0.65) and total peripheral resistance (TPR, r = 0.47). Overall means for night-time ambulatory HR (r = 0.76), SV (r = 0.49), CO (r = 0.45), LVET (r = 0.43), HI (r = 0.82), SBP (r = 0.65), DBP (r = 0.62), MAP (r = 0.63) and TPR (r = 0.20) were not significantly different between visits (P > 0.06). Mean differences (P < 0.01) were observed for PEP (r = 0.57).

CONCLUSIONS

The findings demonstrate that across 2 months in youth daytime and night-time ambulatory bioimpedance-derived measures of HR, HI, SBP, DBP and MAP are highly repeatable and SV, CO, PEP and LVET are moderately repeatable. This methodology should prove useful in cardiovascular research and clinical care.

Cardiovascular reactivity and development of preclinical and clinical disease states

OBJECTIVE

The objective of this review is to evaluate the evidence for the hypothesis that cardiovascular reactivity can predict the development of preclinical (elevated blood pressure, ventricular remodeling, carotid atherosclerosis) and/or clinical cardiovascular disease states.

METHODS

A review of the literature was conducted examining prospective studies.

RESULTS

Three large epidemiological studies with long-term follow-up periods (20 years or more) have found blood pressure responses to the cold pressor task to be predictive of subsequent essential hypertension in initially normotensive samples. Studies showing less consistent results have tended to use shorter-term follow-up periods. A larger body of literature demonstrates consistent associations between stress-related cardiovascular reactivity and blood pressure elevations in youth over the course of 1 to 6 years; such relationships have not been consistently shown among adult samples. Moderately consistent evidence points to a positive relationship between reactivity and other measures of subclinical disease (increased left ventricular mass and carotid atherosclerosis) among the few prospective studies that have examined these issues to date. A number of additional factors, however, such as baseline levels of disease risk and exposure to psychosocial stress, seem to moderate these relationships. Health status at baseline also seems to moderate the association between reactivity and clinical coronary heart disease in recent reports: two of three existing studies in initially healthy samples show no evidence of a relationship between reactivity and clinical outcomes, whereas three of four studies in samples with preexisting coronary heart disease or essential hypertension show a positive relationship between reactivity and subsequent disease states.

CONCLUSIONS

There is reasonable evidence to suggest that cardiovascular reactivity can predict the development of some preclinical states (eg, increased left ventricular mass and blood pressure) states and perhaps even new clinical events in some patients with essential hypertension or coronary heart disease. However, much more information is needed concerning moderating and potentially confounding variables before the robustness of the positive relationships can become clinically useful.

A longitudinal study of ethnic differences in ambulatory blood pressure patterns in youth

BACKGROUND

Many studies demonstrated an ethnic difference in ambulatory blood pressure (BP) patterns. We examined: 1) the stability of this difference; 2) demographic and anthropometric characteristics that predict the difference over 2 years; and 3) the clinical significance of the difference.

METHODS

Recordings were performed 2 years apart on 94 African American and 92 European American youths with a positive family history of hypertension, aged 14 +/- 2 years at initial testing.

RESULTS

African Americans had higher nighttime systolic BP (SBP) on the initial (109 +/- 9 v 105 +/- 8 mm Hg; P < .001) and follow-up (110 +/- 10 v 105 +/- 8 mm Hg; P < .0001) visits despite similar daytime SBP. This was associated with greater left ventricular mass/height2.7 (LVM/height2.7) during the initial (31 +/- 8 v 28 +/- 6 g/height2.7; P < .01) and follow-up (32 +/- 8 v 28 +/- 8 g/height2.7; P < .02) visits. Sex accounted for 17% (P < .0001) of the variance of follow-up daytime SBP in African Americans, and age for an additional 10% (P < .001). In comparison, initial height accounted for 11% (P < .001) of the variance in European Americans. Sex accounted for 18% (P < .0001) of the variance of follow-up nighttime SBP in African Americans, age for an additional 12% (P < .0001), and initial LVM/height2.7 an additional 6% (P < .02). In contrast, sex accounted for 13% of the variance of follow-up nighttime SBP in European Americans, and initial height accounted for an additional 8% (P < .004).

CONCLUSIONS

The pattern of higher nighttime BP despite similar daytime BP in African Americans is stable over time, with sex as the most important predictor of nighttime BP in both groups. This study provides confirmatory data on the clinical significance of the differences.

Cardiovascular (CV) responsivity and recovery to acute stress and future CV functioning in youth with family histories of CV disease: a 4-year longitudinal study

Blood pressure (BP) and heart rate (HR) data obtained during supine rest, in response to and recovery from four laboratory stressors in a baseline year were used to predict supine resting BP and HR values obtained during each of four consecutive annual follow-up evaluations. Subjects were 385 normotensive youth [95 African American (AA) males, 106 AA females, 92 European American (EA) males, 92 EA females] (mean age 12.7+/-2.6 at baseline year) with a positive family history of cardiovascular disease (CVD). During the baseline evaluation subjects were presented with four laboratory stressors (namely, postural change, video game challenge, social competence interview, and parent--child conflict discussion). The BP and HR values taken during each of the laboratory stressors and during the post stressor recovery periods were converted to z-scores which were averaged to yield aggregate measures for systolic and diastolic BP and HR responsivity and recovery. The data obtained during the baseline evaluation were subsequently used to predict the follow-up values of supine resting BP and HR. The prediction models were fairly consistent across each of the 4 follow-up years. Responsivity or recovery accounted for up to 6% of the total variance after accounting for baseline values. Within the prediction models responsivity or recovery accounted for 4--56% of the variance. The predictive value of the derived models did not decline from one annual evaluation to the next over the length of the study. CV recovery may supplement resting and responsivity in the prediction of future development of CVD

Effect of socioeconomic status on the blood pressure in children living in a developing country

BACKGROUND

Lower socioeconomic status has been reported to favor higher blood pressure both during childhood and adulthood, because obesity is more prevalent among this population. The aim of the present study was to evaluate the effect of socioeconomic status on blood pressure and prevalence of obesity among children living in a developing country.

METHODS

Prepubertal primary school children (total number 1024, male/female ratio 513/511, mean age 10.32 +/- 0.60 years) living in Izmir, a metropolis of Turkey, were enrolled in the present study. The children were classified into three groups according to the locations of their schools as those from the well-developed (WD; n = 290), moderately developed (MD, n = 356) and underdeveloped (UD, n = 378) areas. Body mass index (BMI), ratio of BMI to the 50th percentile value of BMI for that age (BMI%) and systolic (SBP) and diastolic blood pressures (DBP) were determined in all children. Each socioeconomic group was subdivided into three subgroups with respect to BMI% as those with less than 90% (SG(< 90)), 90-110% (SG(90-110)), and more than 110% (SG(> 110)). Then, mean SBP and DBP in each subgroup of the WD, MD and UD groups were compared with the corresponding blood pressure values of each other to evaluate the effect of socioeconomic status on the blood pressure. In addition, the SBP and DBP of each subgroup were compared with other subgroups within that group to evaluate the effect of BMI on blood pressure.

RESULTS

The BMI and BMI% of the UD group were significantly lower than that of the WD and MD groups (P < 0.05). In addition, the number of children with a BMI of more than 95% for their age was significantly lower in the UD group compared with the WD and MD groups (1.7, 1.9 and 0.5% in the WD, MD and UD groups, respectively, P < 0.05). The SBP and DBP were positively correlated with BMI% in each group and in all of the subjects cumulatively (r = 0.26, P < 0.001 for SBP and r = 0.34, P < 0.001 for DBP). The SBP and DBP were significantly higher in SG(> 110) than in SG(90-110) and were also higher in SG(90-110) than in SG(< 90) in each group. Mean DBP values in all subgroups of the MD and UD groups were significantly lower than the respective subgroups of the WD group. The SBP of SG(< 90) and SG(90-110) of the UD group were significantly lower than those of the corresponding subgroups of the WD and MD groups.

CONCLUSION

Obesity is not more prevalent among the children of lower socioeconomic classes in Turkey as a developing country. In addition, independent of anthropometric structure, DBP and SBP were shown to be related to the socioeconomic status in childhood age groups and both values were determined to decrease in accordance with a decrease in the socioeconomic level.

Modes of cardiovascular regulation during middle childhood

Obtaining meaningful baseline measures of children's cardiovascular activity (CVA) has been difficult because of constraints inherent to laboratory procedures that are used to assess individual differences in response to stress. To circumvent these problems, we performed repeated baseline measures of pulse rate (PR) and blood pressure for 174 children (aged 7-10 yr) in their natural school setting throughout 2 1-week periods. In addition, experimental assessments of cardiovascular reactivity (CVR) were conducted after each baseline period while children participated in a challenging cognitive task. Multivariate analyses of physiological indices revealed three primary styles of cardiovascular functioning. Two of them, characterizing children either with high PR and low blood pressure or conversely with low PR and high blood pressure, have already been described in the research literature. However, analyses also revealed a third group of children (48% of the subjects) who had both low PR and low blood pressure. Findings indicate developmental differences in cardiovascular regulation and highlight the need to consider both variations in baseline CVA as well as in CVR when examining children's physiological adaptation in everyday settings.